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Technical notes on the EEC-IV.pdf

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EEC-IV Scanning PDF Print E-mail
Maintenance
Written by Christopher Ihara   
 
Hidden behind the passenger side kick panel of your Mustang is the core of your car's performance capabilities - the Ford Electronic Engine Control version Four (EEC-IV, pronounced eek-four).  Using a myriad of sensors, the EEC-IV manages all aspects of your engine's operations from cold starting to Wide Open Throttle.  These sensors monitor things like Barometric Pressure, Coolant Temperature, Air Temperature, Exhaust Oxygen content, throttle position, and many other atmospheric and driver input parameters affecting the engine's performance.

One of the many other capabilities of the EEC-IV is its ability to diagnose a poorly running engine.  Through the use of self-contained sensor tests the EEC-IV can provide information about failed sensors, or sensors picking up abnormal operating conditions which can cause your car to perform poorly.  In addition to these tests, the EEC-IV can also perform cylinder balance checks informing you of individual cylinders which may be experiencing a drop in compression.

This information is stored in the form of numeric codes.  The 5.0 Liter Mustang's EEC-IV has the ability to record and store data from up to 80 start-up cycles in its memory.  Additionally the EEC-IV runs a continuous self-test during normal operation, and errors detected will be stored in the EEC's Keep Alive Memory, or KAM.  These codes can then be extracted from the KAM for diagnosis later.  The codes are referred to as "Continuous Memory Codes" and are stored in the KAM until they are overwritten or the EEC-IV loses power for more than 10 minutes. When these codes are downloaded from the KAM, they will be displayed in a "morse-code" like fashion.  The EEC-IV emits pulses to represent these numeric codes; for example, two pulses, a short pause, then four more pulses would signal a code 24.

The EEC-IV has two different test modes, the first mode is called Key On Engine Off, or KOEO. The second mode is called Key On Engine Running, or KOER, and each mode has a specific purpose.  The first mode KOEO is designed to test all the sensors and ensure that they are functioning within their parameters.  The KOEO mode will also display any startup error codes stored in the KAM.  The KOER mode is designed to analyse the engine while it is running.  Any sensors that detect abnormal engine functionality or that are operating out of specification will generate error codes.  During KOER it is also possible to perform additional tests like the cylinder balance test.

To properly diagnose any problems with your car you must first ensure that all vacuum hoses, connectors, and sensors are properly connected.  Vacuum leaks, missing sensors, corroded, loose, or unplugged connectors will cause diagnosis problems and should be corrected before continuing.

When you have finished correcting any visible problems you may now begin testing the EEC-IV. These codes may then be extracted using one of three different methods. By connecting to the EEC-IV test wiring harness and the Self-Test Input connector you can extract codes using an analog volt-meter, the car's "Check Engine" light, or a commercial code scanner.

Regardless of the method you use to perform EEC-IV diagnostics you will always need to peform the following steps.  

   1. First ensure that the vehicle is turned off.
   2. Fix or replace any disconnected, loose, or missing sensor connections, sensors, or vacuum hoses.
   3. Jumper the connection between the EEC-IV test harness and the Self-Test Input connector.

 

Method One - Analog Volt Meter

Using an analog volt meter is perhaps one of the most popular ways to test the EEC-IV. It requires very few special tools and is quite simple to accomplish.
 
 

 TOOLS SECTION - Method One  Analog Volt Meter

bulletWire Cutters
bulletWire Crimpers
bullet5 feet of red 12 Gauge wire
bullet2 feet of black 12 gauge wire
bullet4 inches of black 12 gauge wire
bullet(3) Three 1/4" Crimp On Male Blade Plugs
bullet(2) Two Crimp On Alligator Clips
 To use an analog volt meter you will need to connect to the positive battery terminal to the positive lead on your volt meter.  You will then connect the negative lead of the volt meter to the EEC-IV test harness as shown. Finally you will jumper the Signal Test Input (STI) into the EEC-IV test harness.

The next few steps are optional, but they will help make testing your EEC-IV much easier.  We're going to make three wire leads that will simplify our test procedures by allowing us to perform all necessary diagnostics from within the car.  The first thing we'll need is a power lead from the battery to the volt meter, the next is a lead from the EEC-IV harness to the volt meter, and finally we'll need a jumper lead from the STI to the EEC-IV test harness.

To make the power lead we will need a five foot section of our red 12 gauge wire. Strip about 1/2 inch of insulation from  both ends of the wire and crimp an alligator clip onto either end.

For the ground lead we will need a two foot section of black 12 gauge wire.  Strip about 1/2 inch of insulation from both ends of the wire and crimp an alligator clip to one end and a 1/4" male blade connector on the other.

Finally for the STI wire we will use a four inch section of black 12 gauge wire.  Strip about 1/2 inch of insulation from both ends of the wire and crimp a 1/4" male blade connector onto either end.

These extra wires will enable us to connect the volt meter to all necessary circuit points and still work from within the vehicle.  This is particularly handy as the EEC-IV does require some input from vehicle controls like the brake pedal and steering wheel.

With the vehicle off, connect the ground lead to the volt meter using the alligator clip and the other end to the EEC-IV test harness using the 1/4" blade connector.  Next, jumper the STI and the EEC-IV test harness using the four inch connector.  Finally, connect the power lead to the volt meter, then to the positive terminal on the battery.  Be very careful not to let the power lead touch anything metal within  the car!  This will ground the circuit and will cause a spark!

To read the codes output by the EEC-IV on your volt meter you will count the number of times the needle sweeps from about 0 volts to 5 volts.  Each sweep of the needle is one pulse from the EEC-IV.  For example if the volt meter were to sweep six times, then pause for one half second, then sweep six more times this would indicate an error code 66.  An error code 66 indicates that no mass air flow signal is present.

Now continue on to the KOEO Testing Procedures section.

 

Method Two - Check Engine Light

One of the easiest ways to test the EEC-IV is to use the check engine light in the instrument cluster. This method is particularly handy because it requires no special tools and only a small jumper wire to perform the test. For simplicity's sake we will make our own jumper wire that you can store in your glove compartment.  
 

TOOLS SECTION - Method Two 

bulletWire Cutters
bulletWire Crimpers
bullet4 inches of black 12 gauge wire
bullet(2) Two 1/4" Crimp On Male Blade Plugs

 
First, cut a four inch section of black 12 gauge wire and strip 1/4" from each end.  Next crimp a 1/4" male blade plug onto either end.

To read the codes output by the EEC-IV on your Check Engine light you will count the number of times the light flashes.  Each flash of the Check Engine light is one pulse from the EEC-IV.  For example if the light were to flash six times, then pause for one half second, then flash six more times this would indicate an error code 66.  An error code 66 indicates that no mass air flow signal is present.

Now continue on to the KOEO Testing Procedures section.

 

Method Three - Commercial Code Scanner

Perhaps the easiest way to read codes is to purchase a readily available scanner made by companies like Actron. Many companies make EEC-IV scanners, some ranging in price from as little as $30 to several hundred dollars depending on their complexity and features.  Ford's STAR tester sells for several hundred dollars and has scanning, data logging, and other capabilities better suited to professional mechanics.

Actron's EEC-IV code scanner sells for around $30 at your local auto parts store and comes with complete instructions and code listings.  You simply plug the code scanner into the EEC-IV test connector and the EEC-IV test connector's ground.  That is all that needs to be done to set up the EEC-IV for testing using a commercial code scanner.

To read the codes output by the EEC-IV on your code scanner you will count the number of times the scanner's LED flashes, or the number of beeps you hear (depending on how you have your scanner configured).  Each flash of the LED (or beep from the scanner) is one pulse from the EEC-IV.  For example if the LED were to flash six times, then pause for one half second, then flash six more times this would indicate an error code 66.  An error code 66 indicates that no mass air flow signal is present.

Now continue on to the KOEO Testing Procedures section.{mospagebreak}

Key On Engine Off (KOEO) Testing Procedures

We have covered three separate methods of testing the EEC-IV so we will need to simplify our descriptions from here on.  Whether you are using the Check Engine light, a volt meter, or a Code Scanner we will simply refer to it as a "reader."  

During the KOEO test the EEC-IV will output codes twice during its display cycle.  For instance if a code 23 and 66 were present the EEC would display 23, 23, 66, 66.  The EEC will display codes in the following order:

   1. Fast codes - used at the factory and are not readable by most scanners.
   2. KOEO codes - any codes generated during the KOEO test.  If everything checks out OK, you should receive a code 11.  These codes will be repeated twice.
   3. Pause of 6 - 9 seconds.
   4. Separator Pulse - this pulse signifies the end of the KOEO codes.
   5. Pause of 6-9 seconds.
   6. Continuous Memory Codes - any codes generated during continuous self-test will be displayed here.  If everything checks out OK, you should receive a code 11.  These codes will be repeated twice.

The following instructions will walk you through the procedures for performing the EEC-IV Key On Engine Off test.

   1. Make sure you have a paper and pencil ready so that you can write down any codes output by the KOEO test.
   2. With your reader disconnected from the EEC-IV diagnostic port, start and run the engine until it is at normal operating temperature.
   3. Shut the engine off and wait 10 seconds, then connect your reader.
   4. With the engine off, and your reader connected, turn the ignition to "Run" but do not start the car.  Throughout this test do not depress the throttle!
   5. You will hear a few clicks and whirrs from the engine bay as solenoids are activated and sensors are tested.  The reader will flash briefly as high speed codes are output by the EEC-IV.  These codes are read at the factory and are not intelligible to most scanners.  Ignore this flash.
   6.  If everything checks out OK you should receive a code "11."  If not, the EEC-IV will display any errors it has received.  Record these code numbers.
   7. After a 6 to 9 second pause your reader should flash once, this is a separator pulse to let you know that no more KOEO codes are present.
   8. After another 6 to 9 second pause your reader will begin receiving Continuous Memory Codes.  If no Continuous Memory Codes are present, you should receive a code "11."  If Continuous Memory Codes are present, your EEC-IV will display each code twice.  Record these numbers.
   9. When all codes have been downloaded turn the ignition to "OFF."
  10. If you wish to perform the test again simply wait ten seconds and then go to step four.
  11. Check your code readings here and correct any problems, then re-run the KOEO test before continuing on to the KOER test.

Note: If you wish to erase your Continuous Memory Codes, deactivate your reader while codes are being output during the KOEO test.
 

Key On Engine Running (KOER) Testing Procedures

After you have corrected any problems in the KOEO test you are now ready to perform the KOER EEC-IV test.  This test checks all sensors and engine functions while they are in their normal operating states.  This test requires up to three inputs from the driver during the test.  The first input requires that the brake pedal be depressed, the second requires that the steering wheel be turned at least one-half turn and then released.  Finally on cars equipped with an E40D automatic transmission, the Overdrive Cancel Switch (OCS) must be deactivated, then reactivated.

As with the KOEO test, the KOER test will output codes twice during its display cycle.  The EEC will display codes in the following order:

   1. Engine Running I.D. Pulse - this pulse is used to identify the type of engine.  The EEC-IV will pulse half the number of cylinders.  For example, on a 5.0 Liter Mustang the EEC-IV will pulse four times, on a 2.3 Liter Mustang it will pulse two times.
   2. Pause of 6 to 20 seconds
   3. Dynamic Response Test - this is a single pulse that indicates that you should briefly move the throttle to Wide Open Throttle (WOT).  This test checks to verify the functinality of the Throttle Position (TP), Mass Air Flow (MAF), and Manifold Air Pressure (MAP) sensors.
   4. Pause of 4 to 15 seconds during this time Fast Codes will be displayed.
   5. KOER codes - any codes generated during the KOER test.  If everything checks out OK, you should receive a code 11.  These codes will be repeated twice.
   6. KOER codes- if you press the throttle to WOT briefly the EEC-IV will begin a cylinder balance test.  When the test has completed its first cycle it will display result codes.  The test will continue to cycle at twice the threshold of the previous test until the engine is shut off.

The following instructions will walk you through the procedures for performing the EEC-IV Key On Engine Off test.

   1. Make sure you have a paper and pencil ready so that you can write down any codes output by the KOEO test.
   2. With your reader disconnected from the EEC-IV diagnostic port, start and run the engine at 2,000 RPM for two minutes.  This will bring the Heated Exhaust Gas Oxygen sensor to its normal operating temperature.
   3. Shut the engine off and wait 10 seconds, then connect your reader.
   4. Connect your reader, and start the car.  Don't depress the throttle unless you receive a Dynamic Response Code.
   5. Your reader will flash your Engine ID Code, if you have a 5.0 Liter Mustang this will be four flashes.  Immediately after you see the Engine ID Code depress the brake pedal, turn the steering wheel at least 1/2 turn, and for E4OD Automatic Transmission cars cycle the Overdrive Cancel Switch.
   6. After a pause of 6 to 20 seconds you may receive a Dynamic Response Code.  This will be a single pulse on your reader that indicates the EEC-IV is requesting a WOT input from you. If you detect this code, briefly depress the throttle to WOT.  Failure to do so will generate an error code.
   7.  After a pause of about 4 to 15 seconds, and if everything checks out OK, you should receive a code "11."  If not, the EEC-IV will display any errors it has received, they will be displayed twice.  Record these code numbers.
   8. Check your code readings here and correct any problems, then re-run the KOER test before continuing on.
   9. Once you have completed the KOER test you may shut off the ignition or continue on with the Cylinder Balance test.{mospagebreak}

EEC-IV Cylinder Balance Testing Procedures

After you have performed the KOER test and corrected any problems you may now perform the EEC-IV Cylinder Balance test.  This test checks all the cylinders in the engine for matched compression ratios. The Cylinder Balance test is designed to help isolate cylinders that have low compression ratios with respect to the others in the engine.  This test is performed immediately after the KOER test has finished displaying codes.

To perform this test, the EEC-IV will bring the idle of the engine up to about 1,000 RPM.  Once the idle has stabilized it will then shut off spark and fuel to one cylinder, during this time the decrease in RPM will be measured. The EEC-IV will then activate fuel and spark to the cylinder being tested, and will wait for several seconds until the idle stabilizes again.  At this time it will repeat the process for the next cylinder, repeating until all have been tested.  The results of the test will then output one or more of the following codes to your reader:

    * 10 - Number 1 Cylinder Low
    * 20 - Number 2 Cylinder Low
    * 30 - Number 3 Cylinder Low
    * 40 - Number 4 Cylinder Low
    * 50 - Number 5 Cylinder Low
    * 60 - Number 6 Cylinder Low
    * 70 - Number 7 Cylinder Low
    * 80 - Number 8 Cylinder Low
    * 90 - Passed Cylinder Balance Test

After the first cycle of the Cylinder Balance test the EEC-IV will then perfrom the Cylinder Balance test again. The test will continue to cycle at twice the threshold of the previous test until the engine is shut off.   Each time the EEC-IV finishes a Cylinder Balance test cycle it will display codes to your reader.

The following instructions will walk you through the procedures for performing the EEC-IV Cylinder Balance test.

    * Make certain that you have completed both the KOEO and KOER tests and have corrected any errors encountered during those tests to make certain that the Cylinder Balance test results will be accurate.
    * After performing the KOER test wait for the EEC-IV to finish displaying codes to your reader, do not shut the engine off!
    * Briefly depress the accelerator to WOT.
    * Write down any codes output by the Cylinder Balance test.
    * Wait for the EEC-IV to perform the next cycle of the Cylinder Balance test.
    * When you are through simply turn the engine off.

While the EEC-IV Cylinder Balance test is not a substitute for a compression check, it can help you determine where to start looking when diagnosing a rough running engine.  It may also help to pin point impending engine problems.

{mospagebreak}

Conclusion

The EEC-IV is a tremendously powerful engine computer.  When you also take into consideration that it was first implemented in 1984 and continued to be used in the Mustang until 1995 it becomes even more impressive.  The average home PC is now obsolete within two years, yet the EEC-IV was powerful enough to last for eleven years!  Granted once you begin asking the EEC-IV to manage a full race engine you will definitely begin to run into some performance limitations; however, for even highly modified street Mustangs the EEC-IV is more than capable of tackling the job.

Take this performance and add in the EEC-IV's easily accessible diagnostic features and the home mechanic is equipped with a powerful tool that he can carry anywhere.  With simple jumpers this tool can be activated whenever he, or she, thinks there may be a problem. Armed with this information it is possible to either fix the problem yourself, or ensure that your mechanic is not taking you for a ride.  If you happen to be at the race track the EEC-IV can help get you rolling again should trouble arise.  All in all we think you'll find the EEC-IV a nice piece of equipment to have in your Mustang toolbox. 

 

 
CODE MEANING ACTION
1 - 8 Cylinder No (as code) low power Cylinder balance test
9 Pass Cylinder balance test
10 Cylinder No. 1 low Cylinder balance test
11 Cylinder No. 2 low Cylinder balance test
12 Cylinder No. 3 low Cylinder balance test
12 Cylinder No. 4 low Cylinder balance test
111 All systems OK  
112 Low voltage air change temperature sensor (ACT) Normal operating temp not reached
113 High voltage air change temperature sensor (ACT) Normal operating temp not reached
114 Out of range voltage air change temperature sensor (ACT) Normal operating temp not reached
116 Out of range Engine coolant temperature sensor (ECT) Normal operating temp not reached
117 Low voltage Engine coolant temperature sensor (ECT) Normal operating temp not reached
118 High voltage Engine coolant temperature sensor (ECT) Normal operating temp not reached
121 Outside range throttle position sensor (TPS)  
122 Low voltage throttle position sensor (TPS)  
123 High voltage throttle position sensor (TPS)  
124 Above spec throttle position sensor (TPS)  
125 Below spec throttle position sensor (TPS)  
126 MAP voltage above spec  
128 MAP sensor/vacuum hose fault  
129 MAF sensor, no MAF change during throttle depression Repeat self test proceedure
136 Lambda sensor (left) mixture lean  
137 Lambda sensor (left) mixture rich  
139 Lambda sensor (left)  
144 Lambda sensor (right)  
157 Low voltage mass air flow sensor (MAF)  
158 HIGH voltage mass air flow sensor (MAF)  
159 Outside range mass air flow sensor (MAF)  
167 Throttle position sensor (TPS). No change during throttle depression Repeat self test procedure
171 Lambda sensor (right)  
172 Lambda sensor (right) too lean  
173 Lambda sensor (right) too rich  
174 Lambda sensor (right) slow response  
175 Lambda sensor (left)  
176 Lambda sensor (left) too lean  
177 Lambda sensor (left) too rich  
178 Lambda sensor (left) slow response  
179 Fuel system lean, part throttle  
181 Fuel system rich, part throttle  
182 Idle mixture too lean Idle speed control vale (ISC)
183 Idle mixture too rich Idle speed control vale (ISC)
184 Above spec manifold air flow sensor  
185 Below spec manifold air flow sensor  
186 Too long injection time pulse width  
187 Too short injection time pulse width  
188 Lambda sensor on left, mixture too lean (part throttle)  
189 Lambda sensor on left, mixture too rich (part throttle)  
191 Idle mixture too lean, left hand Lambda sensor Check EGR valve, check ISC valve
192 Idle mixture too rich, lright hand Lambda sensor Check EGR valve, check ISC valve
193 Flexible fuel sensor circuit  
194 Lambda sensor  
195 Lambda sensor  
211 PIP signal  
212 Tach, circuit, SPOUT grounded. SPOUT circuit, open circuit  
213 Tach, circuit, SPOUT grounded. SPOUT circuit, open circuit  
214 CID circuit failure  
215 #1 Coil  
216 #2 Coil  
217 #3 Coil  
218 Tachometer circuit  
219 Spark timing default to 10 deg rectify SPOUT circuit
220 Tachometer circuit  
221 Spark timing error  
225 Knock sensor  
226 EEC IV/EDIS module pulse  
227 Engine speed/crankshaft position sensor (CPS)  
228 EDIS module/ignition coil winding 1  
229 EDIS module/ignition coil winding 2  
231 EDIS module/ignition coil winding 3  
232 Primary circuit of ignition coil (IGC)  
233 EDIS module  
234 Ignition Coil (IGC)  
235 Ignition Coil (IGC)  
236 Ignition Coil (IGC)  
237 Ignition Coil (IGC)  
238 EDIS module/ignition coil  
239 PIP signal present when cranking  
241 EEC IV/EDIS module, incorrect self test data Repeat self test procedure
243 Coil failure  
244 Cylinder identification fault when power balance requested  
311- 316 Pulse air/thermactar air system faulty  
326 Electronic pressure transducer (EPT)/differential pressure feedback exhaust (DPFE) sensor  
327 Electronic pressure transducer (EPT)/differential pressure feedback exhaust (DPFE) sensor/electronic vacuum regulator (EVR)  
328 Electronic vacuum regulator (EVR)  
332 EGR valve not opening  
334 Electronic vacuum regulator  
335 Electronic pressure transducer (EPT)/differential pressure feedback exhaust (DPFE) sensor  
336 Exhaust pressure too high  
337 Electronic pressure transducer (EPT)/differential pressure feedback exhaust (DPFE) sensor/electronic vacuum regulator (EVR)  
338 Cooling System  
339 Cooling System  
341 Octane adjust (service multiplug) grounded Disconnect for self test, reconnect after
411 Engine speed during self test too low Cure induction leaks, repeat test
412 Engine speed during self test too low Cure induction leaks, repeat test
413 - 416 ISC valve Cure induction leaks, repeat test
452 Vehicle speed sensor  
453 Servo leaking down  
454 Servo leaking up  
455 Insufficient RPM increase  
456 Insufficient RPM decrease  
457 - 458 Speed control fault  
511 ROM fault Battery disconnected, check KAM fuse. if OK module faulty
512 Keep alive memory (KAM) fault Battery disconnected, check KAM fuse. if OK module faulty
513 EEC IV module reference voltage V  
519 Power steering pressure switch (PSPS) not activated during self test Repeat test
521 Power steering pressure switch (PSPS) not activated during self test Repeat test
522 Neutral/drive switch (NDS)  
525 Vehicle in gear or air conditioning on  
528 Clutch switch error  
536 Brake on/off (BOO) switch not activated during self test Repeat test
538 Operating error during self test. Air Conditioning switched on Repeat test
539 Operating error during self test. Air Conditioning switched on Repeat test
542 Fuel pump (FP) circuit failure  
543 Fuel pump (FP) circuit failure  
551 Idle speed control (ISC) circuit failure  
552 Pulse air circuit failure  
554 Fuel pressure regulator control circuit failure  
556 Electrical circuit of fuel pump  
557 Low speed fuel pump circuit  
558 Electrical circuit of (EVR) electronic vacuum regulator  
563 High speed electric drive fan relay/circuit (HEDF) failure  
564 Electronic drive fan relay/circuit (EDF) failure  
565 Canister purge solenoid (CANP)  
566 3rd/4th gear solenoid (ATA)  
573 Electronic drive fan relay/circuit (EDF) failure  
574 High speed electronic drive fan relay/circuit (HEDF) failure  
575 Fuel pump circuit and/or inertia switch circuit  
576 Kick down switch (KDS) Repeat test
577 Kick down switch (KDS) not activated during self test Repeat test
583 Power to fuel pump fault  
612 4/3 switch failed open circuit  
613 4/3 switch failed open circuit  
614 3/2 switch short circuit  
615 3/2 switch failed short circuit  
621 Shift solenoid 1 circuit failed  
622 Shift solenoid 2 circuit failed  
624 EPC solenoid failure  
625 EPC solenoid circuit failure  
628 MLUS Failure  
629 Torque converter lock up clutch solenoid (LUS)  
634 Neutral drive switch (NDS) circuit failure  
635 Transmission temperature switch failure  
637 Transmission temperature switch failure  
639 TSS failure  
645 1st gear failure  
646 2nd gear failure  
647 3rd gear failure  
648 4th gear failure  
649 ETV failure  
651 ETV intermittent failure  
652 MLUS circuit failure  
653 Transmission control switch not activated during self test Repeat test
998 Fault in ECT/ACT/MAF/TPR circuit

 

Electronic Engine Control self test for Ford vehicles with EEC IV

WARNING!
FOLLOW STANDARD SAFETY PRACTICES WHEN WORKING ON A VEHICLE INCLUDING BUT NOT LIMITED TO:

Transmission in Park or Neutral and the driven wheels off the ground or chocked when cranking/running the engine.
Check fan blade for cracks and do not stand next to the fan when engine is running.
Use caution when working on fuel systems, which can remain pressurized for a long period after the key is turned off.
No smoking around fuel.
Watch for electric fan which can come on at any time.
Watch out for hot and/or moving parts.
When working on a no-start vehicle, use a neon spark tester to check for spark and ground the coil wire to prevent accidental starting if spark should occur while testing.
Watch out for high voltage secondary circuits.
If you are not sure of the safety of any operation DO NOT DO IT. ASK SOMEONE!


 

[MAIN TABLE OF CONTENTS/INDEX]
[GLOSSARY]
[2 digit codes] [3 digit codes]

In this chapter:
[Driveability Diagnosis] - A GOOD PLACE TO START
[No-start Diagnosis] - ANOTHER GOOD PLACE TO START (no pun intended)
[Tests] - Key On Engine Off, Key On Engine Running, Cylinder Balance, Wiggle, Memory Erase, Output State Test
[Ignition Timing Tests]
[Intermittent Wiring Faults]
 

CODE TYPES AND FORMATS

TYPES OF CODES

NOTE: Some people have problems distinguishing the different codes. READ THIS SECTION CAREFULLY.
There are drawings of the code formats at the end of this section.

FAST CODES

Fast codes contain the fault information output in the normal slow codes but are output about 100 times faster.
These are the first things output on a Key On Engine Off test.

HARD FAULTS

Hard faults are problems that the computer has located RIGHT NOW. Examples are a sensor out of range or a broken wire (open circuit).

Hard faults are the FIRST set of slow codes output in a Key On Engine Off test. BEFORE the SEPARATOR pulse.

In a Key On Engine Running test, there are ONLY HARD FAULT codes. These are output right after the fast codes.

SEPARATOR PULSE

The separator pulse is a single pulse that indicates the END of hard fault codes and the BEGINNING of memory codes.
It will show up as a code 10 on most digital testers.

MEMORY CODES

Memory codes are problems that the computer has noticed in the past. If for example there was a loose wire to a solenoid that only lost contact while driving but was making contact while testing the system there would be NO HARD FAULT CODE. The code would show up IN MEMORY. The same would happen for a sensor that only went out of range occasionally. Memory codes come out AFTER the separator pulse.

NOTE: The computer will erase the memory after a certain number of engine re-starts if the problem does not repeat itself. The number of re-starts varies from 20 to 80 depending on the year of the vehicle. The later models keep memory longer.

ENGINE ID

The engine ID in a running test is a series of pulses equal to one half the number of engine cylinders. A 4 cylinder engine ID is 2 pulses, a 6 cylinder ID is 3 pulses and an 8 cylinder ID is 4 pulses. A diesel ID is 5.

GOOSE CODE

A "GOOSE" code (also called a dynamic response test) is output during an engine running test. This is a single pulse to signal you to quickly move the throttle approximately 1/2 way down and release.

NOTE: Not all engines give a "GOOSE" code.

CODE FORMATS

Codes are output as a series of pulses. The following charts show the (approximate) timing of the various code pulses.

NOTE: Two digit codes are shown. Three digit codes have similar timing. It just takes a little practice to distinguish between two and three digit types.


 

 

TESTS

[Top of Page]

 

NOTE: Vehicle should be fully warmed for all tests.

HOOKUP

See figure below. EEC IV vehicles have two connectors for self testing the system. They are located on the firewall or the left or right front fender. The large connector contains the self test output (STO) and ground (SIG RTN). The small pigtail is the self test input (STI).

 

KEY ON ENGINE OFF (KOEO) TEST

NOTE: On 4.9L trucks with a manual transmission hold the clutch pedal in during this test.
On Diesel engine trucks hold the throttle to the floor during this test.

1. Make sure engine is fully warmed. If in doubt, run engine at 2000 rpm for 2 minutes.

2. Turn ignition off and wait 10 seconds for system to shut off. Make sure A/C is off and transmission is in Park (automatic) or Neutral (manual).

3. Hook up light and jumper (or a tester if you have one). Turn key to ON (do not start engine).

4. Fast Codes are output (ignore fast light flashes).
NOTE: Unhook self test input jumper (or tester if used) at any time during code output to erase memory.

5. Read hard faults.

6. Separator Pulse.

7. Read memory codes.

8. See code explanations and check components as necessary.
Use FIRST CODE OUTPUT and retest after any repairs are made.

[2 digit codes] [3 digit codes]

KEY ON ENGINE RUNNING (KOER) TEST

1. Make sure engine is fully warmed. If in doubt, run engine at 2000 rpm for 2 minutes.

2. Turn ignition off and wait 10 seconds for system to shut off. Make sure A/C is off and transmission is in Park (automatic) or Neutral (manual).

3. Hook up light and jumper (or tester if you have one).

4. Make sure vehicle is safe to run and start engine.

5. Engine I.D. should be output.

6. Step on brake and turn steering wheel 1/4 turn.
If the vehicle has an overdrive cancel switch, push it.

7. If a "Goose" pulse is received, move throttle quickly 1/2 way down and release.

8. Fast Codes are output (ignore).

9. Read codes.

10. See code explanations and check components as necessary.
Use FIRST CODE OUTPUT and retest after any repairs are made.

[2 digit codes] [3 digit codes]

CYLINDER BALANCE TEST

NOTE: This test is only available on Sequential Fuel Injection (SFI) Engines.

Start an engine running test and press the accelerator lightly within 2 minutes after the last code is output. The PCM will cancel each cylinder in turn and measure the RPM drop. If any weak cylinders are noted their number will be output as a multiple of 10 (e.g. 30, 40). The output is the actual cylinder number, not the number in the firing order. NOTE: Will not always pinpoint bad injectors.

WIGGLE TEST

Engine running or engine off tests

Hook up for a self test but do not hook up the self test trigger. Turn key to on. Hook up the trigger, wait 10 seconds and disconnect. Hook up trigger again . Tap suspected sensors (be careful if engine is running), wiggle the wiring harnesses etc. IF the PCM picks up a fault the self test output will pulse and a memory code will be stored (The value of this is questionable. I NEVER located a problem with it. - JT).

MEMORY ERASE

To erase the memory disconnect the self test trigger while the codes are being output. You COULD also disconnect the battery but then the PCM forgets some important running characteristics.

OUTPUT STATE TEST

NOTE: Do not perform on E4OD diesel.

Run the KOEO test all the way through and leave the test hooked up.

Cycle throttle 3/4 open and closed while watching tester, light or voltmeter. Self test output will switch with every throttle activation. On some testers (like my old pocket testers) the light will only pulse every other push. But the outputs still switch EVERY time.

Solenoids (EGR etc.) will switch on or off with every throttle activation (push throttle they're on, push throttle they're off). You should be able to hear clicks as the solenoids switch states. The test will work for most solenoids: AIRB, AIRD, BOOST, EGR, EVR (NOTE: EVR does not click but vacuum cycles).

Here's a graphic example of Output State test.

 

 

IGNITION TIMING TESTS

[Top of Page]

 

NOTE: Timing is not adjustable on Electronic Ignition

Engine off. Unplug the SPOUT connector in the (usually) yellow wire coming from the distributor connector (either in-line or shorting plug see figure below).


 

Restart engine, and with a timing light, set to specifications on decal (usually 10 degrees BTDC). Shut off engine and reconnect SPOUT wire.

To check timing advance the SPOUT must be hooked up. Start a running EEC test and when test starts (RPM's go up) check the timing.
It should be advanced about 20 degrees (plus or minus 3 degrees) more than the original base timing. Since base timing is usually 10 degrees BTDC then the advance is usually to 30 degrees BTDC.

 

INTERMITTENT WIRING FAULTS

[Top of Page]

 

The first thing to do for wiring faults is an inspection. Checking the wiring CAREFULLY can make a long job into a quick one. Get into the habit of doing a quick wire harness check first.

Typical bad spots are where wiring runs across engine brackets or body parts. If you see a harness that's laying on any of these areas pick it up and look underneath for shiny metal showing through.

If you have a persistent problem that needs to be fixed, there are a few ways you can check for intermittent faults.

TO CHECK FOR A SHORT TO GROUND:

Key OFF. Disconnect PCM and all other parts that the suspect wire hooks to (e.g. the EGR Vent (EGRV) solenoid). Hook a 12 volt test light clip to battery POSITIVE and the other end of the lamp to the suspect wire. Wiggle, bend and move the wire everywhere it runs. If it shorts to ground, the test light will light.

You can use a meter in the same way but a light is more attention getting.

TO CHECK FOR A SHORT TO POWER:

Key OFF. Disconnect the PCM and all other parts that the suspect wire hooks to (e.g. the Constant Control Relay Module (CCRM)). Hook a 12 volt test light clip to battery NEGATIVE and the other end of the lamp to the suspect wire. Wiggle, bend and move the wire everywhere it runs. If it short to power, the test light will light.

Again, you can use a meter in the same way but a light is easier.

TO CHECK FOR AN OPEN CIRCUIT:

Key OFF. Disconnect the PCM and all other parts that the suspect wire hooks to (e.g. the transmission).

ON THIS TEST IT IS VERY IMPORTANT YOU ARE SURE EVERYTHING IS DISCONNECTED..

Ground one end of the suspect wire. Whichever end is easier at the PCM end or the other.

Hook a 12 volt test light clip to battery POSITIVE and the other end of the lamp to the opposite end of the suspect wire from where you hooked the ground. The light should light. Wiggle, bend and move the wire everywhere it runs. If it opens, the test light will go out.

Again, you can use a meter in the same way but a light is easier.
 

EEC IV 2 DIGIT CODES

[MAIN TABLE OF CONTENTS/INDEX]
[GLOSSARY]

[EEC Tests]

NOTE: When you see "is/was" listed for a code:
For a HARD fault code the sensor IS out of range right now.
For a MEMORY code, it WAS out of range at one time (possible intermittent wire etc.).

Some codes pertain to more than one system but there will be only one of the systems on the vehicle.
For example code 58. A vehicle with a VAT sensor will not have an Idle Tracking Switch.

Differences in test mode noted as:

(O) = Key On Engine Off test
(R) = Key On Engine Running test
(M) = Memory code

 

NOTE: Greyed out links to component tests are not functional in these samples.

11 System checks OK -

12 Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too low) - ISC

13 (O) ISC did not respond properly (extends to touch throttle then retracts for KOEO) - ISC
(R) Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too high)
(M) ISC sticking, open ITS circuit or TP sticking

14 Ignition pickup was erratic - Ignition Systems
E4OD Transmission diesel RPM sensor - Diesel RPM sensor

15 (O) No Keep Alive Memory power to PCM pin 1 or bad PCM (Memory Test Failure)
(M) KAM (pin 1) was interrupted (was battery disconnected ?)

16 1.9L & 2.5L - Throttle stop set too high - IDLE or Idle Set Procedures
2.3L - RPM's too low - IDLE
(O) Electronic ignition - IDM circuit fault - Ignition Systems

17 1.9L & 2.5L - Throttle stop set too low - IDLE
 

18 (R) Check base timing & advance function - Timing Tests
(M) Ignition TACH signal erratic - Ignition Systems

19 (O) No Vehicle Power (pins 37 + 57) or bad PCM VPWR Diagnosis
(R) Erratic idle during test (reset throttle & retest) - Idle Set Procedures
Electronic ignition Cylinder ID sensor/circuit problem - Ignition Systems

21 Engine Coolant Temperature (ECT) sensor out of range - ECT

22 MAP (vacuum) or BARO signal out of range - MAP

23 Throttle sensor out of range or throttle set too high - TPS

24 Intake Air Temperature (IAT) or Vane Air Temperature (VAT) sensor out of range - IAT VAT

25 Knock sensor not tested (ignore if not pinging) - KS

26 Mass Air Flow (MAF) or Vane Air Flow (VAF) out of range - MAF VAF
Transmission Oil Temperature (TOT) sensor out of range - Transmissions

27 Vehicle Speed Sensor problem - VSS

28 Vane Air Temperature (VAT) sensor out of range - VAT
2.3L w/Electronic Ignition - Cyl ID, IDM low or right coil pack failure - Ignition Systems

29 Vehicle Speed Sensor problem - VSS

EGR CODES DEPEND ON WHAT SYSTEM TYPE THE VEHICLE IS EQUIPPED WITH:
 

EVP is for vehicles equipped with EGR solenoid(s), with or without an EVP sensor

EVR is for vehicles equipped with an EGR Vacuum Regulator (EVR) and an EGR Valve Position (EVP) sensor

PFE is for vehicles with Pressure Feedback EGR (PFE) sensor and and an EGR Vacuum Regulator (EVR)

If you don't know what type of system you have, go to the EVP heading, which is the first one.
There are pictures under the different headings to help you identify the system.

31 EVP - (O, R, M) EVP signal is/was out of range - EVP
EVR - (O, R, M) EVP signal is/was low - EVR
PFE - (O, R, M) PFE signal is/was low - PFE

32 EVP - (R) EGR not responding properly during test - EVP
EVR - (O, R, M) EVP signal is/was low - EVR
PFE - (R, M) PFE shows low pressure, EGR not seating or memory, not seating intermittently - PFE

33 ALL - (O, M) EGR did not open/ respond during test or if memory code, did not open intermittently - EVP EVR PFE

34 EVP - (R) EGR did not respond properly during test - EVP
EVR - (O, R, M) EVP sensor is/was high - EVR
PFE - (O, R, M) PFE sensor is/was out of range - PFE

35 EVP - (R) Engine RPM's too low to test EGR system - EVP
EVR - (O, R, M) EVP sensor signal is/was high - EVR
PFE - (O, R, M) PFE sensor signal is/was high - PFE

38 Idle Tracking Switch signal was intermittent - ISC

39 Transmission Torque Converter clutch not engaging - Transmissions

40 SERIES FUEL/AIR INJECTION CODES ON VEHICLES WITH DUAL OXYGEN SENSORS REFER TO THE RIGHT OR REAR SENSOR. EXCEPT: 1984-1988 3.8L ENGINES: LEFT SENSOR

41 (R) System lean - Fuel control
(M) System was lean for 15 seconds or more (no HO2S switching) - Fuel control

42 (R) System rich - Fuel control
(M) System was rich for 15 seconds or more (no HO2S switching) - Fuel control

43 (R) HO2S sensor not reading (run at 2000 rpm's for 2 minutes and retest - check for HO2S switching)
(M) Was lean at WOT for 3 seconds or more - Fuel control

44 AIR system inoperative - Air Injection

45 AIR not Diverting (AIRD) - Air Injection
Electronic Ignition - coil primary circuit failure - Ignition Systems

46 AIR Bypass (AIRB) not working - Air Injection
Electronic Ignition - primary circuit failure coil 2 - Ignition Systems

47 Low flow unmetered air (check for small vacuum leaks, injector o'rings, gaskets etc.)
E4OD transmission 4x4 switch/circuit problem - Transmissions

48 High flow unmetered air (check for large vacuum leak, inlet hoses etc.)
Electronic Ignition - coil primary circuit failure - Ignition Systems

49 Electronic Ignition - spout signal circuit problem - Ignition Systems
Transmission 1/2 shift problem - Transmissions

51 Engine Coolant Temperature (ECT) sensor signal is/was too high - ECT

52 Power Steering Pressure Switch/circuit open - PSP
(R) Did you turn wheel during test ?

53 Throttle Position sensor too high - TPS

54 Intake Air Temperature (IAT) or Vane Air Temperature (VAT) signal high - IAT VAT

55 No or low (under 7.5 V) Key Power to PCM pin 5

56 Vane Air Flow (VAF) or Mass Air Flow (MAF) sensor high - VAF MAF
Transmission Oil Temperature sensor too high - Transmissions

57 Intermittent in Park/Neutral/ Switch or Neutral Pressure switch circuit - PNP or Transmissions
1990 Scorpio - Octane jumper installed (information only code - to inform you if it is installed or not)

58 Idle Tracking Switch (ITS) signal problem ISC
Vane Air Temperature (VAT) sensor out of range or open - VAT

59 AXOD 4/3 circuit fault - Transmissions
3.0L SHO - Low speed fuel pump circuit problem - Power / Fuel Pump Circuits
Transmission 2/3 shift problem - Transmissions
1990 Scorpio - Idle jumper installed (information only code - to inform you if it is installed or not)

61 Engine Coolant Temperature (ECT) sensor is or was too low - ECT

62 AXOD (KOEO only) 3/2 circuit short to ground - Transmissions
AXOD (KOEO AND KOER) 4/3 circuit failure - Transmissions
E4OD excessive converter clutch slippage - Transmissions

63 Throttle Position Sensor (TPS) signal too low TPS

64 Intake Air Temperature (IAT) or Vane Air Temperature (VAT) signal low or grounded - IAT VAT

65 Check intermittent HO2S (signal or ground) - Fuel Control
(R) E4OD truck - cycle OD cancel switch after engine ID is received - Transmissions
1984 3.8L ONLY - O, M Battery voltage high (check for electrical system overcharging)

66 Vane Air Flow (VAF) or Mass Air Flow (MAF) signal low - VAF MAF
Transmission Oil Temperature (TOT) signal low (possibly grounded) - Transmissions

67 Park/Neutral circuit fault - PNP
Transmission Manual Lever Position (MLP) sensor circuit - Transmissions
(M) Intermittent Park Neutral Position (PNP) sensor fault - PNP

68 Idle Tracking Switch (ITS) circuit (possibly grounded) - ISC
Vane Air Temperature (VAT) sensor out of range or grounded - VAT
3.8L AXOD -Transmission Temperature Switch (TTS) open - Transmissions
Electronic Transmission - Transmission Oil Temperature (TOT) sensor was overheated - Transmissions

69 AXOD transmission (O) 3/2 switch closed (possible short circuit) - Transmissions
AXOD (M) 3/2 switch open (poss short to power) - Transmissions
E4OD 3/4 shift problem - Transmissions

70 (M) 3.8L AXOD - Data link to instrument cluster fault. Service any other EEC codes, erase memory and retest.
If code is still present refer to instrument cluster diagnosis manual.

71 (M) 1.9L TBI, 2.3L TBI, 2.5L TBI - ITS signal was grounded when throttle should have been opening ITS - ISC
ISC motor problem or Idle Tracking Switch (ITS) signal wire shorted to ground - ISC
(M) 1.9L MFI - PCM re-initialized. Possible electrical noise, case ground or intermittent VPWR problem - VPWR Diagnosis
(M) 3.8L AXOD - Data link to instrument cluster fault - See code 70

72 (R) No MAP or MAF change in "goose" test - retest, check for frequency or voltage change - MAP MAF
(M) 1.9L MFI - VPWR circuit to PCM was intermittent - VPWR Diagnosis
(M) 2.3L T/C - PCM re-initialized. Possible electrical noise, case ground or intermittent VPWR problem - VPWR Diagnosis
(M) 3.8L AXOD - Message center data link circuit fault - See code 70
 

73 (O) Rerun test, if 73 is still output replace TPS
(R) No Throttle Position Sensor (TPS) change in "goose" test. Must get at least 25% throttle rotation - TPS

74 Was brake depressed after engine ID was received ?
Brake On Off (BOO) signal open or short to ground - BOO

75 Brake On Off (BOO) signal shorted to power - BOO

76 Vane Air Flow (VAF) did not respond to "goose" test - VAF
 

77 System did not receive "goose" test - see TESTS

78 (M) VPWR circuit to PCM was intermittent or the PCM is bad VPWR Diagnosis

79 A/C is on or pin 10 is shorted to power

80 SERIES CODES GENERALLY ARE CIRCUIT PROBLEMS THAT COULD BE WIRING, RELAY OR SOLENOID RELATED.
ONLY ONE OF THE CIRCUITS LISTED UNDER THE CODE IS USED ON EACH VEHICLE. THE FAULT IS IN WHICHEVER SOLENOID OR CIRCUIT IS PRESENT ON THE VEHICLE

81 Boost control solenoid - Solenoids
AIRD solenoid - Solenoids and Air Injection
3.0L SHO - Inlet Air Solenoid - Solenoids

82 2.3L TC - Fan Control wire shorted to ground - A/C and Fan Circuits
AIRB solenoid - Solenoids and Air Injection
3.8L SC - Super Charger Bypass Solenoid - Solenoids

83 High Electro Drive Fan circuit fault - A/C and Fan Circuits
EGR Control solenoid - Solenoids
3.0L SHO - Low Speed Fuel Pump Relay circuit - Power / Fuel Pump Circuits

84 EGR Vacuum Regulator - Solenoids
EGR cutoff solenoid - Solenoids
EGR Vent solenoid - Solenoids

85 2.3L T/C Automatic - 3/4-4/3 Shift solenoid - Transmissions
CANP solenoid (ALL 1989) - Solenoids
(M) 1.9L MFI - System has corrected rich condition - Fuel control

86 2.3L or 2.9L Truck - A4LD 3/4 shift solenoid - Transmissions
(M) 1.9L MFI - System has corrected lean condition - Fuel control

87 (O) Fuel pump circuit fault (check inertia switch) - Power / Fuel Pump Circuits
Vehicles with 2BBL carb - Temperature Compensated Accelerator Pump Solenoid - Solenoids
(M) intermittent in fuel pump primary circuit - Power / Fuel Pump Circuits
NOTE: On some Escorts with automatic seat belts this code is normal IN MEMORY due to the wiring

88 Throttle Kicker Solenoid - Solenoids
Variable Voltage Choke relay circuit fault - VVC
Fan Control circuit fault - A/C and Fan Circuits
A4LD - Converter Clutch Override solenoid - Transmissions
Electronic Ignition - IDM, DPI or spout circuit fault - Ignition Systems

89 A4LD - Converter Clutch Override solenoid - Transmissions
AXOD Torque Converter Control solenoid circuit - Transmissions
Exhaust Heat Control (heat riser) solenoid circuit - Solenoids

90 SERIES FUEL/AIR INJECTION CODES ON VEHICLES WITH DUAL OXYGEN SENSORS REFER TO THE LEFT OR FRONT SENSOR. EXCEPT: 1984-1988 3.8L ENGINES: RIGHT SENSOR

91 (R, M) System running lean - Fuel control
Transmission SS 1 circuit/solenoid problem - Transmissions

92 (R) System running rich - Fuel control
Transmission SS 2 circuit/solenoid problem - Transmissions

93 (O) Throttle linkage binding or bad ISC motor ISC (R) HO2S not reading - Fuel control
Transmission TCC circuit/solenoid problem - Transmissions

94 AIR system inoperative - Air Injection
Transmission TCC circuit/solenoid problem - Transmissions

95 (O) Fuel pump: open, bad ground or always on - Power / Fuel Pump Circuits
(R) AIR not Diverting (AIRD) - Air Injection
(M) Possible bad fuel pump ground or open between fuel pump and pin 8 at PCM (Fuel Pump Monitor signal) - Power / Fuel Pump Circuits

96 (O) Fuel pump monitor circuit shows no power - Power / Fuel Pump Circuits
(R) AIR Bypass (AIRB) not working - Air Injection
(M) (Service 87 code first if present) Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits

97 E4OD OD cancel light circuit failure - Transmissions

98 (R) Did not pass KOEO yet (Get 11 in KOEO first)
Transmission EPC circuit/solenoid failure - Transmissions

99 (R) ISC needs to learn (Let idle for 2 minutes; Erase memory and retest)
Transmission EPC circuit/solenoid failure - Transmissions
 

EEC IV 3 DIGIT CODES

[MAIN TABLE OF CONTENTS/INDEX]
[GLOSSARY]

[EEC Tests]

Applicable only to some 1991 and up vehicles

NOTE: When you see "is/was" listed for a code:
For a HARD fault code the sensor IS out of range right now.
For a MEMORY code, it WAS out of range at one time (possible intermittent wire etc.).

Differences in test mode noted as:

(O) =Key On Engine Off test
(R) =Key On Engine Running test
(M) =Memory code

 

NOTE: Greyed out links to component tests are not functional in these samples.

111 System checks OK

112 (O,M) Intake Air Temperature (IAT) sensor is/was low or grounded - IAT

113 (O,M) IAT sensor is/was high or open - IAT

114 (O,R) IAT sensor out of range - IAT

116 (O,R) Engine Coolant (ECT) sensor out of range - ECT

117 (O,M) ECT sensor is/was low or grounded - ECT

118 (O,M) ECT sensor is/was high or open - ECT

121 (O,R,M) Throttle Position (TP) sensor out of range - TPS

122 (O,M) TP low (possibly grounded or open circuit) - TPS

123 (O,M) TP is/was high or short to power - TPS

124 (M) TP voltage was higher than expected - Fuel control

125 (M) TP voltage was lower than expected - Fuel control

126 (O,R,M) MAP or BARO sensor out of range - ">MAP

128 (M) MAP vacuum has not been changing - check vacuum lines - ">MAP

129 (R) No MAP or Mass Air Flow sensor change during "goose" test - MAP MAF

136 (R) Oxygen sensor not switching/system lean Left or Front HO2S - Fuel control
 

137 (R) Oxygen sensor not switching/system rich Left or Front HO2S - Fuel control
 

138 (R) Fault in Cold Start Injector circuit - Fuel control
 

139 (M) Oxygen sensor not switching Left or Front HO2S - Fuel control
 

144 (M) Oxygen sensor not switching Single, Right or Rear HO2S - Fuel control
 

157 (R,M) Mass Air Flow signal is/was low or grounded - MAF

158 (O,R,M) MAF sensor is/was high or short to power - MAF

159 (O,R) MAF sensor is/was out of range - MAF

167 (R) No Throttle Position sensor change in "goose" test (must get at least 25% rotation) - TPS

171 (M) Oxygen sensor not switching - system was at adaptive limits - Single, Right or Rear HO2S - Fuel control
 

172 (R,M) Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control
 

173 (R,M) Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S - Fuel control
 

174 (M) Oxygen sensor was slow in switching Single, Right or Rear HO2S - Fuel control
 

175 (M) Oxygen sensor not switching - system was at adaptive limits - Left or Front HO2S - Fuel control
 

176 (M) Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control
 

177 (M) Oxygen sensor not switching - system was rich Left or Front HO2S - Fuel control
 

178 (M) Oxygen sensor was slow in switching Left or Front HO2S - Fuel control
 

179 (M) Fuel system was rich at part throttle Single, Right or Rear HO2S - Fuel control
 

181 (M) Fuel system was lean at part throttle Single, Right or Rear HO2S - Fuel control
 

182 (M) Fuel system was rich at idle Single, Right or Rear HO2S - Fuel control
 

183 (M) Fuel system was lean at idle Single, Right or Rear HO2S - Fuel control
 

184 (M) Mass Air (MAF) output higher than expected - Fuel control
 

185 (M) Mass Air (MAF) output lower than expected - Fuel control
 

186 (M) Injector pulse width longer than expected or Mass Air Flow (MAF) lower than expected - Fuel control
 

187 Injector pulse width shorter than expected or Mass Air Flow (MAF) higher than expected - Fuel control
 

188 (M) Fuel system was rich at part throttle - Left or Front HO2S - Fuel control
 

189 (M) Fuel system was lean at part throttle - Left or Front HO2S - Fuel control
 

191 (M) Fuel system was rich at idle - Left or Front HO2S - Fuel control
 

192 (M) Fuel system was lean at idle - Left or Front HO2S - Fuel control
 

193 Failure in Flexible Fuel (FF) sensor circuit - Fuel control
 

194 (M) Perform cylinder balance test to check for inoperative injectors

195 (M) Perform cylinder balance test to check for inoperative injectors

211 (M) Ignition PIP signal was erratic or missing - Ignition Systems

212 (M) Ignition TACH signal was erratic (module/wiring) or SPOUT circuit fault - Ignition Systems

213 (R) Ignition SPOUT or SAW circuit open or shorted - Ignition Systems

214 (M) Error in Cylinder ID (CID) circuit or signal - Ignition Systems

215 (M) Primary circuit failure - ignition coil 1 - Ignition Systems

216 (M) Primary circuit failure - ignition coil 2 - Ignition Systems

217 (M) Primary circuit failure - ignition coil 3 - Ignition Systems

218 (M) IDM signal open or high or left coil pack failure - Ignition Systems

219 (M) SPOUT circuit failure, timing defaulted to 10 degrees - follow code 213 diagnosis

222 (M) IDM open or high or right coil pack failure - Ignition Systems

223 (M) Dual Plug (DPI), SPOUT or IDM circuit fault - Ignition Systems

224 (M) Failure in ignition coil primary circuit - Ignition Systems

225 (R) Knock sensor not tested (ignore if not pinging) - KS

226 (O) Ignition Diagnostic Monitor (IDM) signal fault - Ignition Systems

232 (M) EI primary coil circuit failure - Ignition Systems

238 (M) EI primary circuit failure - ignition coil 4 - Ignition Systems

311 (R) AIR system not working - Single, Right or Rear HO2S - Air Injection

312 (R) AIR not diverting - Air Injection

313 (R) AIR not bypassing - Air Injection

314 (R) AIR inoperative, Left or Front HO2S - Air Injection

326 (R,M) Pressure Feedback EGR shows low pressure EGR not seating or not seating intermittantly - PFE

327 (O,R,M) EGR feedback signal is/was low - EVR or PFE

328 (O,R,M) EGR Valve Position (EVP) is/was low - EVR

332 (R,M) EGR did not open/respond during test or if memory code, did not open intermittantly - EVR or PFE

334 (O,R,M) EVP sensor is/was high - EVR

335 (O) EGR feedback signal is/was out of range - EVR or PFE

336 (O,R,M) PFE sensor signal is/was was high - ">PFE

337 (O,R,M) EGR feedback signal is/was was high - EVR

338 (M) Cooling system did not heat up (check cooling system / thermostat operation)

339 (M) Cooling system overheated (check cooling system / thermostat operation)

341 (O) Octane jumper installed (information only code to notify you if it is installed)

411 (R) Idle speed system not controlling idle properly (generally idle too high) - ISC

412 (R) Idle speed system not controlling idle properly (generally idle too low) - ISC

452 (M) Vehicle Speed Sensor (VSS) problem

511 (O) No power to PCM pin 1 or bad PCM (processor)

512 (M) Memory power (PCM pin 1) was interrupted - Was battery disconnected ?

513 (O) Replace processor (PCM) (internal failure)

519 (O) PSP switch/circuit open - PSP

521 (R) Wheel not turned during test or PSP problem - PSP

522 (O) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault - PNP
Transmission MLP sensor out of range in park - Transmissions

524 Problem in low speed fuel pump circuit - Power / Fuel Pump Circuits

525 (O,M) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault - PNP

528 (M) System shows voltage at pin 10 (is A/C on ?) or pin 30 (PNP, CPP switch) - PNP

529 (M) Data Communications Link to processor failure
Service any EEC codes, erase memory and retest. If code is still present refer to instrument cluster diagnosis manual.

533 (M) Data Communications Link to instrument cluster failure - see 529

536 (O,R,M) Brake On Off open or shorted to ground - BOO

538 (R) System did not receive "goose" test - TESTS

539 (O) System shows voltage at PCM pin 10. Is A/C on ?

542 (O,M) Fuel pump open, bad ground or always on - - Power / Fuel Pump Circuits

543 (O) Fuel pump monitor circuit shows no power - Power / Fuel Pump Circuits
(M) (Service 556 code first if present) Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits

551 Problem in Intake Manifold Runner Control (IMRC) solenoid/circuit - Solenoids

552 (O) AIRB solenoid/circuit failure - Solenoids

553 (O) AIRD solenoid/circuit failure - Solenoids

554 (O) Fuel Press Regulator Control solenoid/circuit fault - Power / Fuel Pump Circuits

556 (O,M) Fuel pump relay primary circuit fault - Power / Fuel Pump Circuits

557 (O,M) Low speed pump relay primary circuit fault - Power / Fuel Pump Circuits

558 (O) EGR vacuum regulator solenoid/circuit failure - EVR or PFE or Solenoids

559 (O) A/C relay primary circuit fault - A/C and Fan Circuits

563 (O) High Fan Control (HFC) circuit failure - A/C and Fan Circuits

564 (O) Fan Control (FC) circuit failure - A/C and Fan Circuits

565 (O) Canister Purge 1 solenoid/circuit failure - Solenoids

566 (O) transmission 3/4 shift solenoid/circuit - Transmissions
 

569 (O) Canister Purge 2 solenoid/circuit failure - Solenoids

578 (M) A/C pressure sensor VREF short to ground - A/C and Fan Circuits

579 (M) ACP sensor did not change with A/C on - A/C and Fan Circuits

581 (M) Cooling fan current was excessive - A/C and Fan Circuits

582 (O) Open cooling fan circuit - A/C and Fan Circuits

583 (M) Fuel pump current was excessive - Power / Fuel Pump Circuits

584 (M) Open power ground circuit - Power / Fuel Pump Circuits

585 (M) A/C clutch current was excessive - A/C and Fan Circuits

586 (M) Open circuit in A/C clutch - A/C and Fan Circuits

587 (O, M) Communication problem between PCM and Variable Control Relay Module (VCRM) - Power / Fuel Pump Circuits

617 (M) Transmission shift failure (1/2 shift) - Transmissions

618 (M) Transmission shift failure (2/3 shift) - Transmissions

619 (M) Transmission shift failure (3/4 shift) - Transmissions

621 (O) Solenoid/circuit failure - shift solenoid 1 - Transmissions

622 (O) Solenoid/circuit failure - shift solenoid 2 - Transmissions

624 (O,M) Solenoid/circuit failure -Electronic Pressure Control (EPC) current is high - Transmissions

625 (O,M) Solenoid/circuit failure - Electronic Pressure Control (EPC) current is low - Transmissions

626 (O) Transmission Coast Clutch (CCS) Solenoid/circuit fault - Transmissions

627 (O) Torque Converter Clutch circuit fault - Transmissions

628 (M) Excessive converter clutch slippage - Transmissions

629 (O,M) Torque Converter Clutch circuit fault - Transmissions

631 (O) Overdrive Cancel Light circuit problem - Transmissions

632 (R) E4OD - Transmission Control Switch (TCS) should be cycled once between engine ID and Goose test

633 (O) 4x4L switch should be in 4x2 or 4x4 high for the test

634 (O,M) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault
Electronic shift transmission - Manual Lever Position (MLP) sensor out of range in PARK - Transmissions

636 (O,R) Transmission Oil Temperature (TOT) sensor out of range - Transmissions

637 (O,M) TOT sensor is/was high or open - Transmissions

638 (O,M) TOT sensor is/was low or grounded - Transmissions

639 (R,M) Transmission Speed sensor (TSS) circuit fault - Transmissions

641 (O) Transmission solenoid/circuit failure Shift Solenoid 3 - Transmissions

643 (O)(M) Torque Converter Clutch (TCC) circuit - Transmissions

645 (M) Transmission 1st gear failure - Transmissions

646 (M) Transmission 2nd gear failure - Transmissions

647 (M) Transmission 3rd gear failure - Transmissions

648 (M) Transmission 4th gear failure - Transmissions

649 (M) Transmission EPC system failure - Transmissions

651 (M) Transmission EPC solenoid/circuit fault - Transmissions

652 (O) Torque Converter Clutch (TCC) circuit fault - Transmissions

654 (O) Transmission selector not in PARK - Transmissions

656 (M) Torque Converter Clutch (TCC) slip - Transmissions

657 (M) Transmission temperature was excessive - Transmissions

998 (R) Did not pass Key On Engine Off test yet (Get 111 in KOEO first)
(O) Transmission Electronic Pressure Control (EPC) solenoid/circuit fault - Transmissions