2.3l Cec Tests W/codes Ford Mustang III рестайлинг

DIAGNOSTIC FORMATS

There are 2 diagnostic formats used to test and service the EEC-IV system: QUICK TEST and CIRCUIT TESTS. A DIAGNOSIS BY SYMPTOM chart is available to identify specific problems and reference specific CIRCUIT TESTS, if no Key On Engine Off (KOEO) or Key On Engine Running (KOER) fault code is identified.

Always start with the QUICK TEST procedures before attempting any CIRCUITS TESTS. The QUICK TEST procedure is designed to allow the technician to identify problems and retrieve service codes. The CIRCUIT TESTS give procedures for testing circuits and checking sensors and actuators. If a vehicle passes the QUICK TEST procedures, and there are no driveability problems, the EEC-IV system is okay. Problem exists somewhere else besides the EEC-IV system. If an intermittent driveability problem exists, use the KOER "Wiggle" Test procedure to set a code or identify the problem.

KOEO & KOER SELF-TEST Codes

All service codes are 2 digit numbers which are generated one digit at a time. These codes indicate a current fault in the system. They should be serviced in the order in which they appear. Use the appropriate code chart to find the correct CIRCUIT TEST. Codes are shown as voltage pulses (needle sweeps) on an analog Volt/Ohmmeter (VOM).

If a VOM is being used, pay careful attention to the length of the pauses in order to read the codes correctly. There will be a 1/2 second pause between the number of sweeps indicating a digit and a 2 second pause between each digit in a code. There will be a 4 second pause between each code. The KOEO SELF-TEST memory codes are separated from the Continuous Memory codes by a 6 second delay, a single 1/2 second sweep (Separator), and another 6 second delay. Always record the codes in the order received.

If a scan tool diagnostic tester is used, it will count the pulses and display them as a digital code. The STAR tester will add a zero (0) to single digit Separator (10) and Dynamic Response (10) codes. The Dynamic Response code is displayed in the KOER SELF-TEST. (Scheme 42)

If the "CHECK ENGINE" light is used, service codes will be displayed as flashes. On Continental models, the "MESSAGE CENTER" may be used to display codes. (Scheme 43)

Separator Pulse

A single 1/2 second separator pulse is issued 6-9 seconds after last functional KOEO Self-Test code. Then 6-9 seconds after the single 1/2 second separator pulse, the continuous memory codes will be displayed.

Continuous Memory Codes

These codes are issued as a result of information stored by the ECA during continuous self test monitoring. These codes are displayed during the KOEO SELF-TEST after the separator pulse code. These codes should be used for diagnosis, ONLY when KOEO and KOER SELF-TEST results in a Code 11 (pass code) and all QUICK TEST steps have been successfully completed. There are a few exceptions which may be checked after the KOEO SELF-TEST codes have been repaired. These codes indicate a fault that has been recorded within the last 40 key starts. The fault may or may not be currently present.

Fast Codes

At the start of the KOEO testing and after the WOT request in the KOER test there is an output from the ECA known as "Fast Codes". These are short bursts of information that are used by the manufacturer during assembly. With most equipment these code bursts are not visible as the whole code sequence lasts less than 1/2 second. Ignore this fluctuation if noticed with your test equipment.

CLEARING CODES

Service codes are retrieved from the EEC-IV system through the Self-Test connector by using various test equipment. The KOEO and KOER SELF-TESTS are used for this purpose. After these codes have been recorded or repaired, they may be cleared from the ECA memory.

To clear continuous memory codes, run the KOEO SELF-TEST, when service codes begin to appear on your test equipment or "Check Engine" light, disconnect the jumper wire from the STI connector. If using a STAR tester, unlatch the center button. This will erase continuous memory codes from the processor's memory. If a problem has not been corrected, or the fault is still present, the code will be immediately reset into the ECA memory.

TEST EQUIPMENT

The following equipment is recommended to diagnose and test EEC-IV system. Some equipment is REQUIRED to perform tests. DO NOT attempt to test this system without proper equipment. Damage to vehicle components may result if improper equipment is used.

1. The Self-Test Automatic Read-Out (STAR) Diagnostic Tester (Rotunda 007 00004 ) or SUPER STAR II (Rotunda 007-00028 ) is recommended but not required. It is specially built for the EEC-IV system and is used to display the 2-digit (numeric) service codes that are programmed into the control module. There are also a number of aftermarket scan tool testers available.
2. Analog Volt/Ohmmeter (VOM) with 0-20V DC range. This can be used as an alternate to diagnostic tester, to read codes only.
3. Digital Volt/Ohmmeter (DVOM) with minimum 10-megohm input impedance.
4. Breakout Box (Rotunda 014-00322). This is a jumper wire assembly which connects between the vehicle harness and the ECA. The breakout box is REQUIRED to perform certain tests on the system. Ford Motor Co. specifically states that back -probing will cause PERMANENT DAMAGE to the ECA 60-pin connector. The "test pin No." called out in CIRCUIT TESTS refers to Test Pin numbers on breakout box. Once the breakout box has been installed during a test sequence, it may remain connected for the remainder of that test unless otherwise specified. Aftermarket breakout boxes are available.
5. Vacuum gauge with 0-30 in. Hg range and resolution (units on scale) of 1 in. Hg.
6. Tachometer with 0-6000 RPM range, accuracy +/- 40 RPM, and a resolution of 20 RPM.
7. Vacuum pump with 0-30 in. Hg range.
8. Timing light.
9. Spark Tester (D81P-6666-A or ST-125). A modified side electrode spark plug IS NOT sufficient for these testing procedures.
10. Fuel Injection Pressure Gauge (T80L-9974-A).
11. 12-volt test light (non-powered type).
12. Jumper wire, about 15" long.
13. MAP/BP Tester. This unit plugs into MAP/BP sensor circuit and DVOM to check input and output signals. The MAP sensor produces a frequency signal which may be checked using a scope with a millivolt scale or a DVOM that measures frequency.

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

HOW TO USE QUICK TESTS

The QUICK TEST diagnostic procedure is a functional test of the EEC-IV system. It consists of 7 basic test steps. These basic steps must be carefully followed in sequence, otherwise misdiagnosis, or replacement of non-faulty components may result.

1. VISUAL CHECK & VEHICLE PREPARATION
2. EQUIPMENT HOOK-UP
3. KEY ON ENGINE OFF (KOEO) SELF-TEST
4. COMPUTED TIMING CHECK
5. KEY ON ENGINE RUNNING (KOER) SELF-TEST
6. CONTINUOUS MONITOR MODE (WIGGLE TEST)
7. DIAGNOSIS BY SYMPTOM

After all tests, servicing, or repairs have been completed, repeat QUICK TEST to ensure all EEC-IV systems work properly.

The KOEO and KOER SELF-TESTS are intended to detect faults present at the time of testing, not intermittent faults. Intermittent faults are recorded and stored as Continuous Memory Codes, or may be detected by CONTINUOUS MONITOR MODE "WIGGLE" TEST, which is entered after the KOER SELF-TEST. A fault discovered during the "Wiggle" Test, may or may not set a code in the Continuous Memory, but the "Wiggle" Test is always circuit specific as directed in the CIRCUIT TESTS.

Note. Correct test results for system are dependent on the correct operation of several related non-EEC components and systems. All non-EEC problems in the engine, ignition or fuel system should be corrected before attempting to diagnose the EEC system.

VISUAL CHECK & VEHICLE PREPARATION

Before hooking up any equipment to diagnose the EEC system, make the following visual checks and perform the preparation procedures

1. Verify condition of air cleaner and air ducting.
2. Check all vacuum hoses for leaks, restrictions, and proper routing.
3. Check the EEC-IV system wiring harness electrical connections for corrosion, bent or broken pins, loose wires or terminals, and proper routing.
4. Check the ECA, sensors and actuators for physical damage.
5. Check engine coolant level.
6. Perform all necessary safety precautions to prevent personal injury or vehicle damage.
7. Set parking brake and place shift lever in "P" for automatic transmissions, and Neutral for manual transmissions. DO NOT move shift lever during test unless specifically directed to do so.
8. Turn off all lights and accessories. Ensure vehicle doors are closed when making voltage or resistance readings.
9. Start engine and idle until upper radiator hose is hot and pressurized, and throttle is off fast idle. Check for leaks around exhaust manifold, exhaust gas oxygen sensor, and vacuum hose connections.
10. Turn ignition off. Service items as required, then go to «EQUIPMENT HOOK-UP»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) .

SELF-TEST CONNECTOR LOCATIONS

Analog Volt/Ohmmeter (VOM)

1. Turn ignition switch to "OFF" position. Set VOM at 0-15V DC range and connect positive lead of VOM to positive battery terminal.
2. Connect negative VOM lead to pin No. 4 (STO) on Self-Test connector. (Scheme 47) Connect timing light, and go to KOEO SELF-TEST. KOEO SELF-TEST is activated by connecting jumper wire from Self-Test Input (STI) pigtail to pin No. 2 (Signal Return) on Self-Test connector with the ignition on.

STAR Tester

Turn ignition switch to "OFF" position. Connect color coded adapter cable leads to diagnostic tester. Connect adapter cable's 2 service connectors to vehicle Self-Test and STI connectors. Connect timing light. Go to KOEO SELF-TEST.

With ignition on, connect a jumper wire between STI and pin No. 2 of Self-Test connector. No additional special equipment hookup is required. (Scheme 45)

Scheme 47

Scheme 48

Key On Engine Off (KOEO) - Self-Test Special Notes

When preparing to perform the Key On Engine Off (KOEO) self-test. Be aware of the following conditions

1. It may be necessary to service non-EEC-IV faults before running Key On Engine Off (KOEO) Self-Test.
2. Continuous Memory Codes recorded in this step will be used for diagnosis in Continuous Self Test after a PASS code 11 is received in both the Key On Engine Off (KOEO) and the Key On Engine Running (KOER) Self-Tests. See «CONTINUOUS SELF TEST»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes).
3. Deviation from this procedure may cause the output of false codes.
4. The first set of codes to appear are the KOEO SELF-TEST codes, they will be repeated twice, followed by the SEPARATOR pulse signal and then the CONTINUOUS MEMORY codes [KOEO-Separator-Continuous Memory]. These codes will also be repeated twice. Example: for a code display of 11-1(0)-11. The first number 11 is a KOEO code 11, the second number is a separator code 10, and the third number is a continuous code 11. An illustration of this code sequence may be found in (Scheme 42) - (Scheme 46).

Key On Engine Off (KOEO) Self-Test - Test Procedure

Note. This test procedures has been revised based on updated procedures in Ford Technical Service Bulletin, 89-18A-10.

1. Turn ignition switch to "OFF" position. Ensure all procedures of «VISUAL CHECK & VEHICLE PREPARATION»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__visual-check-vehicle-preparation) and «EQUIPMENT HOOK-UP»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) have been followed. Engine should be at normal operating temperature.
2. Activate the KOEO Self-Test.
3. Turn ignition switch to the "ON" position. If Star Tester is being used latch center button in down position at this time. If using an analog VOM, connect a jumper wire from Self-Test Input (STI) pigtail to pin No. 2 (Signal Return) on Self-Test connector. (Scheme 42)and (Scheme 44). If using "Check Engine" (MIL) light, connect a jumper wire from Self-Test Input (STI) pigtail to pin No. 2 (Signal Return) on Self-Test connector. This will activate the KOEO Self-Test, "Check Engine" (MIL) light will start to flash.
4. The ECA will run through a test cycle, opening and closing various solenoids and switches. After the completion of the test cycle the codes will appear. Record all codes.

Test Procedure - Code Output

Code Output, indications and actions to be taken.

1. Code Output [11-1(0)-11] Both tests indicate a PASS. Action to take: If engine idles rough or runs rough, Go to «D19 - SYSTEM CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d19-system-check) , step 2). If this symptom is not present; Go to «COMPUTED TIMING CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__computed-timing-check) . If engine is a no start, go to «A1 - NO START»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) .
2. Code Output [Any Code(s)-1(0)-11] KOEO tests indicates a FAULT. Action to take: Go to KOEO service codes. See «KOEO SELF-TEST - CIRCUIT TEST & STEP MENU (2.3L)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) . Always start with the first code displayed.
3. Code Output [11-1(0)-Exceptions] Continuous Memory indicates a FAULT. Action to take: DO NOT service continuous memory codes at this time. If engine idles rough or runs rough, go to «D19 - SYSTEM CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d19-system-check) , step 2). If this symptom is not present, go to «COMPUTED TIMING CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__computed-timing-check) . Refer to code output. See «KOEO CONTINUOUS MEMORY CODE EXCEPTIONS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) . Service only the KOEO CONTINUOUS MEMORY CODE EXCEPTIONS at this time. All other Continuous Memory Codes will be serviced after a Code 11 is displayed during the KOER SELF-TEST.
4. Code Output [Any Code(s)-1(0)-Any Code(s)] Both tests indicate a FAULT. Action to take: DO NOT service CONTINUOUS MEMORY CODES at this time. Go to KOEO service codes. See «KOEO SELF-TEST - CIRCUIT TEST & STEP MENU (2.3L)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) . Always start with the first code displayed.
5. Code Output [11-1(0)-15] Action to take: Go to «D15 - CODE 15 KOEO CONTINUOUS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d15-code-15-koeo-continuous) .

KOEO Continuous Memory Code Exceptions

KOEO continuous memory code (any code(s) except) list. Only codes that apply to vehicle being diagnosed are listed. See KOEO CONTINUOUS MEMORY CODE EXCEPTIONS table.

KOEO CONTINUOUS MEMORY CODE EXCEPTIONS

No Starts

If engine does not start, go to A1 - NO START , step 1). Proceed through this test procedure until engine is running and then repeat KOEO SELF-TEST. If engine stalls or is unable to complete KOEO SELF-TEST, diagnosis by symptom may be used until engine is able to complete KOEO SELF-TEST. See DIAGNOSIS BY SYMPTOM .

No Codes Displayed Or Codes Displayed Not Listed

The KOEO SELF-TEST did not activate or non-system codes were displayed. Repeat KOEO SELF-TEST to verify condition. If condition still exists go to D14 - NO CODES/CODES NOT LISTED , step 1).

COMPUTED TIMING CHECK

1. Turn key off and wait 10 seconds. Start engine. Activate KOER SELF-TEST. After the last service code has been displayed, the timing will remain fixed for 2 minutes, unless KOER SELF-TEST is deactivated.
2. Correct Self-Test timing equals base ignition timing (10 degrees BTDC on most engines, see emission decal) plus 17-23 degrees BTDC. If timing is not 27-33 degrees BTDC, go to CIRCUIT TEST «D13 - SPARK TIMING CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d13-spark-timing-check) . If timing is 27-33 degrees BTDC, proceed with KOER SELF-TEST.

Description

This test checks engine sensors under actual operating conditions and at operating temperature. The ECA operates and tests actuators and sensors during this test. A number of special test procedures may be requested by the ECA during this test, depending on vehicle equipment. These tests allow the ECA to test the following sensors.

Engine ID Codes

The first code displayed during the KOER SELF-TEST is an engine identification code. They indicate the number of cylinders in the engine. An engine ID Code of 2 (20), 3 (30), or 4 (40) indicates 4, 6, or 8 cylinder engines, respectively.

Dynamic Response or Wide Open Throttle (WOT) Check

Allows the ECA to check the TP, VAF and MAP sensors. This test is accomplished by a brief opening of the throttle to the full open position. It is also called the "Goose" test. It is requested by a single pulse or Code 10 approximately 6-20 seconds after the engine identification codes are displayed.

Special Notes

When preparing to perform the Key On Engine Off (KOEO) self-test. Be aware of the following conditions

1. If the engine starts but stalls, or stalls during Self-Test. Go to «D19 - SYSTEM CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d19-system-check) , step 1).
2. On vehicles equipped with the Brake On/Off Switch (BOO), the brake pedal MUST be depressed and released AFTER the ID code.
3. On vehicles equipped with the Power Steering Pressure Switch (PSPS), within 1 to 2 seconds after the ID code, the steering wheel must be turned at least one-half turn and released.
4. The Dynamic Response code is a single pulse (or a 10 code on the Scan Tester) that occurs 6-20 seconds after the engine running identification code. See «DYNAMIC RESPONSE OR WIDE OPEN THROTTLE (WOT) CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__dynamic-response-or-wide-open-throttle) .
5. When the Dynamic Response code occurs, perform a brief wide-open throttle.
6. Code Output [Engine ID-Dynamic Response-Engine Running] display description. Example: for a code display of 2(0)-1(0)-11, the first number 2 is Engine ID, this 2 indicates a four cylinder. The second number is a Dynamic Response code 10, and the third number is a Engine Running code 11. Also, see «ENGINE ID CODES»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__engine-id-codes) .

Test Procedure

Note. This test procedure has been revised due to Ford Technical Service Bulletin 89-18A-10.

1. Deactivate Self-Test by disconnecting STI jumper wire. Start and run engine at 2000 RPM for 2 minutes to warm up HEGO sensor. Turn engine off and wait 10 seconds
2. Activate "Self-Test". See «KEY ON ENGINE OFF (KOEO) SELF-TEST»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) .
3. Start engine. The engine ID code will be displayed. On vehicles equipped with Brake On/Off switch (BOO), the brake pedal MUST be depressed and released AFTER the ID code (within 1-2 seconds). On vehicles equipped with Power Steering Pressure Switch (PSPS), the steering wheel MUST be turned one-half turn and released AFTER the ID code. On vehicles equipped with an Overdrive Cancel Switch (OCS) the switch must be cycled AFTER the ID code.
4. If a Dynamic Response code occurs, briefly depress accelerator pedal to Wide Open Throttle (WOT). A Dynamic Response code is a Code 1 or 10 displayed after the Engine ID code and before the Engine Running codes. DO NOT depress throttle during test unless a Dynamic Response code occurs. The KOER Self-Test service codes will then be displayed. Observe and record all codes.

Test Procedure (Code Output)

Code Output, indications and actions to be taken.

1. Code Output [Eng. ID(0)-1(0) or No display-11] KOER Self-Test indicates a PASS. Action to take: If Continuous Memory Codes were present, Go to «CONTINUOUS SELF TEST»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) . If Continuous Memory is a PASS Code 11 and a symptom is present, Go to «DIAGNOSIS BY SYMPTOM»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__diagnosis-by-symptom) .
2. Code Output [Eng. ID(0)-1(0) or No Display-11] KOER Self-Test indicates a FAULT. Action to take: Go to KOER service codes. See «KOER SELF-TEST - CIRCUIT TEST & STEP MENU (2.3L)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) under KOER CODE/TEST MENU. Always start with the first code displayed.
3. Code Output [98-No Display-Any Code(s)] Code 98 in place of the I.D. code indicates that the vehicle is in FMEM (Failure Mode Effects Management), see «FAILURE MODE EFFECTS MANAGEMENT (FMEM), CODE 98»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__failure-mode-effects-management-fmem-code) under DIAGNOSTIC AIDS. Key On Engine Off (KOEO) Self-Test DID NOT PASS. Engine Running Self-Test will not initiate until a PASS Code 11 is obtained in KOEO Self-Test. Action to take: Perform Key On Engine (KOEO) Off Self-Test and address all codes displayed. Go to «KEY ON ENGINE OFF (KOEO) SELF-TEST»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) . Always start with the first code displayed.
4. Code Output [No Code Display-Codes Not Listed] Indicates Self-Test did not activate. Action to take: Rerun Key On Engine Running Self-Test to verify the above condition. If condition is still present. Go to «D14 - NO CODES/CODES NOT LISTED»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d14-no-codescodes-not-listed) .

1. Verify that a PASS 11 was received in both Key On Engine Off (KOEO) and Key On Engine Running (KOER) Self-Tests before continuing with this test.
2. Refer to «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__continuous-monitor-mode-wiggle-test) for a detailed description of how to use the Continuous Monitor Mode.
3. If Continuous Memory is a PASS code 11 and a symptom is present. GO to «DIAGNOSIS BY SYMPTOM»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__diagnosis-by-symptom) .

Determining The Continuous Memory Codes To Be Serviced

1. Refer to the Continuous Memory Codes recorded from KOEO Self-Test.
2. The cause of some of the Continuous Memory Codes may have been eliminated during either Key On Engine Off or Engine Running Self-Test service.
3. Address only those Continuous Memory Codes for which faults have not been previously serviced. If the fault has been serviced in KOEO Self-Test for Computed Timing Check. Clear Continuous Memory Codes.
4. Go to service codes table of Continuous Self-Test. See «CONTINUOUS MEMORY - CIRCUIT TEST & STEP»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) .

CONTINUOUS MONITOR MODE (WIGGLE TEST)

The Continuous Monitor Mode allows a technician to attempt to recreate an intermittent fault while monitoring the system. This mode, also called the "Wiggle" test, may be used in both KOEO and KOER modes. The CIRCUIT TESTS specify the use of this procedure to identify intermittent faults in specific circuits or components.

KOEO "Wiggle" Test Procedure

Connect test equipment. (Scheme 44) Turn ignition on and activate Self-Test with jumper lead or diagnostic tester. Wait 10 seconds, deactivate, and then reactivate Self-Test. You are now in "Wiggle" test mode. Tap, move, and wiggle the suspected sensor and/or harness area. If a fault is detected, a service code may be stored in memory and indicated at the diagnostic tester or scan tool. Record or retrieve code and perform test indicated in CONTINUOUS MEMORY - CIRCUIT TEST & STEP table.

KOER "Wiggle" Test Procedure

Connect test equipment. (Scheme 44) Turn ignition off and wait 10 seconds. Start engine. Activate Self-Test with jumper lead or diagnostic tester. Wait 10 seconds, deactivate, and then reactivate Self-Test. DO NOT turn engine off. You are now in engine running "Wiggle" test mode. Tap, move, and wiggle the suspected sensor and/or harness area. If a fault is detected, a service code may be stored in memory and indicated at the diagnostic tester or scan tool. Record or retrieve code and perform test indicated in CONTINUOUS MEMORY CODES table.

DIAGNOSIS BY SYMPTOM

A pass code (11-10-11), indicates there are no active codes in the KOEO or KOER SELF-TEST. If driveability symptoms still exist and the EEC system is still suspect, go to SYMPTOM/TEST MENU for referral to the appropriate CIRCUIT TEST.

DIAGNOSTIC AIDS

A number of additional diagnostic test features are available to aid in diagnosis of driveability problems.

Output State Check

The Output State Check is used as an aid in servicing output actuators associated with the EEC-IV system. It allows you to energize and de-energize most of the system output actuators on command. This mode is entered from the KOEO SELF-TEST after all codes have been received. At this time, leave SELF-TEST activated and depress throttle to initiate the test sequence. Each time throttle is depressed and released, the output actuators will change state (go from on to off, or off to on).

Failure Mode Effects Management (FMEM), Code 98

The FMEM mode allows system operation when one or more sensors fail or transmit signals which are out of their normal operating range. The ECA will substitute a mid-range signal for the defective sensor and continue to monitor the sensor. If the faulty sensor signals return to within the normal operating range the ECA will use those signals. A Code 98 will be displayed when the FMEM mode is in effect.

Cylinder Balance Test

The cylinder balance test is an aid in finding a weak or noncontributing cylinder in engines equipped with SEFI fuel systems. The ECA shuts off the fuel supply to each injector and measures the RPM drop. It computes the variation between the cylinders and identifies any weak ones. This test mode is entered during the KOER SELF-TEST after all codes have been displayed. Within 2 minutes after the codes have been displayed lightly depress throttle (a 2-3 degree throttle angle is required, NOT a wide open throttle). After a brief stabilizing period the ECA will activate the test procedure. The test will be repeated if the throttle is depressed within 2 minutes of the final code output. During the 2nd and 3rd test sequence the percentage of allowable variation between cylinders will be reduced. Service codes displayed during this test correspond to cylinder number and indicate a weak or non-contributing cylinder. If Code 90 is displayed during this test it indicates a pass. If Code 77 is displayed, repeat cylinder balance test. If throttle is moved during this test, Code 77 will appear, indicating that test was not completed. Total test time is about 3 minutes.

CYLINDER BALANCE TEST SERVICE CODES

ECA PIN VOLTAGE & RESISTANCE CHECKS

The ECA pin voltage chart may be helpful when diagnosing hard-to-find problems. It must be used with a EEC-IV breakout box and a high impedance DVOM. The voltages and resistances shown are typical component values. Actual measured values may differ slightly from those shown. Always check wiring diagrams for actual pin callouts as some models may vary slightly, depending on equipment.

Components shown may not be on all vehicles. The engine should be at normal operating temperature and run at 2000 RPM for about 2 minutes and returned to idle. Always refer to the appropriate CIRCUIT TEST to diagnose a suspected faulty component.

FREQUENTLY USED EEC-IV ABBREVIATIONS

FREQUENTLY USED EEC-IV ABBREVIATIONS

ECA SENSOR RESISTANCE & PIN VOLTAGE REFERENCE CHART - INPUTS

ECA SENSOR RESISTANCE & PIN VOLTAGE REFERENCE CHART - OUPUTS

KOEO CODE/TEST MENU

KOEO SELF-TEST - CIRCUIT TEST & STEP MENU (2.3L)

KOER CODE/TEST MENU

KOER SELF-TEST - CIRCUIT TEST & STEP MENU (2.3L)

CONTINUOUS CODE/TEST MENU

CONTINUOUS MEMORY - CIRCUIT TEST & STEP

SYMPTOM/TEST MENU

DIAGNOSIS BY SYMPTOM (SYMPTOM-TO-CIRCUIT TEST MENU)

Service Code Definitions - 2.3L OHC MPFI. Scheme 49

Service Code Definitions - 2.3L HSC MPFI. Scheme 50

Service Code Definitions - 2.3L TC MPFI. Scheme 51

HOW TO USE CIRCUIT TESTS

1. DO NOT perform any CIRCUIT TEST unless directed to do so by a QUICK TEST procedure. Ensure all non-EEC related faults are corrected. FOLLOW EACH TEST STEP IN ORDER UNTIL FAULT IS FOUND. DO NOT replace any part unless directed to do so. When more than one service code is received, start with the first code displayed.
2. CIRCUIT TESTS require that you prove the electrical circuits are okay before you replace sensors or any other components. Always test circuits for continuity between the sensor and the ECA. Test all circuits for shorts to power, opens, or shorts to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with KOEO or as specified in CIRCUIT TESTS.
3. DO NOT measure voltage or resistance at ECA or connect any test light, unless specified in testing procedure. All measurements are made by probing REAR of connector. Isolate both ends of a circuit and turn key off whenever checking for shorts or continuity, unless specified. NOTE: When directed in testing procedure to service or repair TFI ignition system, see «IGNITION SYSTEM - TFI-IV»(/ford/mustang/iii-1986-1993/remont/ignition-system/#ignition-system-tfi-iv) article in ENGINE section.
4. Disconnect solenoids and switches from harness before measuring continuity, resistance, or applying voltage. After each repair, check all component connections and repeat CIRCUIT TEST.
5. An "open" is defined as any resistance reading greater than 5 ohms. This specification tolerance may be too high for some items in the EEC-IV system. If resistance approaches 5 ohms, always clean the suspected connector and coat with protective dielectric silicone grease. A "short" is defined as any resistance reading less than 10K ohms to ground, unless otherwise specified in CIRCUIT TEST.
6. On FUEL CONTROL CIRCUIT TESTS C1, and C2, to prevent replacement of good components, be aware that the following non-EEC related areas may also be at fault. These areas include ignition coil, distributor cap and rotor, spark plug wires, fouled spark plugs, canister purge problems, EGR valve and gasket, air filter, poor power and ground circuits, fuel pressure, intake and exhaust manifold leaks, engine not at normal operating temperature, and problems with PCV valves or fuel contaminated engine oil. NOTE: Fuel contaminated engine oil may affect some service codes. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter.
7. On FUEL CONTROL CIRCUIT TESTS C1, and C2, vacuum leaks in non-EEC related areas may also cause code 41 or 91 to be displayed. Check for unmetered air leaks between airflow meter and throttle body, leaking vacuum motors, engine seals, EGR system, PCV system, Canister Purge (CANP) problems, or contaminated HEGO sensor. Code 42 or 92 may be caused by fuel contaminated engine oil, ignition misfire, EGR system, or CANP problems. NOTE: In the following tests, circuits and illustrations are supplied courtesy of Ford Motor Co. NOTE: CIRCUIT TESTS are grouped in the following categories. A1-A3 Preliminary Tests B1-B15 Input Sensor Tests C1-C2 Fuel Control Systems D1-D24 ECA Output Tests

TFI Module Circuits (Part 1 of 4). Scheme 52

TFI Module Circuits (Part 2 of 4). Scheme 53

TFI Module Circuits (Part 3 of 4). Scheme 54

TFI Module Circuits (Part 4 of 4). Scheme 55

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuel quantity and quality, ignition system damage, cracks, moisture, etc., engine mechanical conditions such as bad valves, timing belt, etc. Also included are starter and battery circuit problems.

1. Starting System. Try to start engine. If engine does not crank, check vehicle starting and charging systems. Ensure fuel pump inertia switch is set (button pushed in). If engine cranks, but does not start or stalls after starting, go to next step.
2. Checking VREF Signal at TPS. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect Throttle Position Sensor (TPS). Turn key on, leaving engine off (KOEO). Measure voltage at TPS harness connector between (VREF) and SIGNAL RETURN. If reading is less than 4 volts or more than 6 volts, go to CIRCUIT TEST A3, step 1). If reading is between 4 and 6 volts, reconnect TPS and go to next step.
3. Checking For Spark At Plugs. Disconnect any spark plug wire and connect spark tester between plug wire and engine ground (On 2.3L DIS truck, disconnect exhaust side spark plug only). Crank engine and check for spark. If spark exists, connect spark plug wire and go to step 12). If there is no spark, connect spark plug wire and go to next step or to step 5) for vehicles equipped with DIS.
4. Checking For Spark at Coil. Remove high tension coil wire from distributor and install spark tester. Check for spark while cranking engine. If spark exists, connect coil wire and service or repair TFI ignition system. If no spark exists, connect coil wire and go to next step.
5. Ignition Ground Continuity. Turn key off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale and disconnect TFI or DIS (pins No. 7-12). Measure resistance between test pin No. 16 and TFI harness connector ground. If reading is more than 5 ohms, repair harness and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
6. Isolating SPOUT Circuit Fault. Install breakout box. Connect TFI or DIS (pins No. 7-12). Connect ECA to breakout box. Set breakout box switch to "DISTRIBUTOR" position. Try to start vehicle. If vehicle starts, go to step 10). If vehicle does not start, go to next step.
7. Checking SPOUT Signal. With KOEO, connect breakout box and ECA. Move breakout box timing switch to "COMPUTED" position. Set DVOM on 20-volt scale and measure voltage between test pin No. 36 and chassis ground while cranking engine. If voltage is between 3 and 6 volts, EEC system is NOT at fault. TFI ignition system should be diagnosed. If voltage is less than 3 volts or more than 6 volts, go to next step.
8. Checking SPOUT and PIP For Shorts. Turn key off and wait 10 seconds. With breakout box installed, disconnect ECA. Disconnect TFI (on 2.3L Truck disconnect DIS pins No. 1-6). Set DVOM on 200K-ohm scale. On SPOUT circuit, measure resistance between test pin No. 36 (SPOUT) and test pins No. 16, 20, 40, 46, and 60 for short to ground. Measure resistance between test pin No. 36 and test pins No. 26, 37 and 57 for short to power. Measure resistance between test pins No. 36 and 56 for short to PIP. On PIP circuit, measure resistance between test pin No. 56 and test pins No. 16, 20, 40, 46, and 60 for short to ground. Measure resistance between test pin No. 56 and test pins No. 26, 37 and 57 for short to power. Measure resistance between test pins No. 56 and 36 for short to SPOUT. If any reading is less than 10K ohms, repair short in harness and repeat QUICK TEST. If engine still does not start, go to next step. If all readings are 10K ohms or more, go to next step.
9. Isolating Shorts In Processor. Turn key off and wait 10 seconds. With breakout box installed, connect ECA, but leave TFI or DIS disconnected. Set DVOM on 200K ohm scale. On SPOUT circuit, measure resistance between test pin No. 36 (SPOUT) and test pins No. 37 and 57 for short to power. Measure resistance between test pin No. 36 and test pins No. 40 and 60 for short to ground. On PIP circuit, measure resistance between test pin No. 56 (PIP) and test pins No. 37 and 57 for short to power. Measure resistance between test pin No. 56 and test pins No. 40 and 60 for short to ground. If any reading is less than 500 ohms, replace ECA and repeat QUICK TEST. If all readings are greater than 500 ohms, connect TFI and go to next step.
10. Checking PIP Signal. With key off, install breakout box. Set DVOM on 20-volt scale. On 2.3L Truck with DIS, switch timing switch to "DIST" on breakout box. Measure voltage between test pins No. 56 and 16, while cranking engine. If reading is between 3 and 7 volts, remove breakout box. Replace ECA and repeat QUICK TEST. If reading is less than 3 volts or more than 7 volts, go to next step (on 2.3L DIS Truck, switch timing switch on breakout box to "COMPUTED" position).
11. Continuity of PIP Circuit. Install breakout box, turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect ECA and TFI (on 2.3L Truck, disconnect DIS pins No. 1-6). Measure resistance between test pin No. 56 and TFI connector PIP circuit. If reading is 5 ohms or more, repair open PIP circuit and repeat QUICK TEST. If readings is less than 5 ohms, go to next step.
12. Verifying SPOUT Signal. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damaged pins, corrosion, or loose wires. Repair as necessary. Install breakout box and connect ECA. Ensure breakout box timing switch is in "COMPUTED" position. Set DVOM on 20-volt scale and measure voltage between test pin No. 36 and test pins No. 40 and 60 while cranking engine. If reading is between 3 and 6 volts, go to step 13). If reading is less than 3 volts or more than 6 volts, go to step 8). CAUTION: Use safety precautions when working on fuel system. No smoking or open flame. If fuel starts leaking, immediately turn key off.
13. Fuel Pump Check. Connect pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning key on for one second and observe pressure gauge. Turn key off, and wait 10 seconds. Repeat sequence 5 times. If pressure increased, go to «D19 - SYSTEM CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d19-system-check) , step 1) for MPFI and SEFI fuel injected engines. Go to «D19 - SYSTEM CHECK»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d19-system-check) , step 2) for CFI fuel injected engines. If pressure did not increase, go to next step.
14. Inertia Switch Check. Turn key off. Locate fuel pump inertia switch and ensure push button on switch is pushed down in the "ON" position. Set DVOM on 200-ohm scale. Measure resistance of switch. If resistance is greater than 5 ohms, replace switch. If resistance is less than 5 ohms, go to «C1 - FUEL CONTROL - ALL APPLICATIONS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__c1-fuel-control-all) , step 1).

A2 - VEHICLE BATTERY

Note. Perform this test when directed here by CIRCUIT TEST A3, C2, or D13 test procedures.

Vehicle Battery Circuits (Part 1 of 4). Scheme 56

Vehicle Battery Circuits (Part 2 of 4). Scheme 57

Vehicle Battery Circuits (Part 3 of 4). Scheme 58

Vehicle Battery Circuits (Part 4 of 4). Scheme 59

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: battery cables and ground straps, voltage regulator, alternator, or ignition switch. This test is intended to diagnose the ECA, power relay, battery voltage and the following harness circuits

1. Signal Return
2. STO
3. STI
4. Ground
5. VPWR
6. KAPWR
7. VREF
8. Ignition

1. Battery Voltage Check. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage across battery terminals. If reading is less than 10.5 volts, service or replace discharged battery. If reading is 10.5 volts or more, go to next step.
2. Checking EEC Ground Circuit. Turn key off and wait 10 seconds. Inspect ECA connector and pins. Install breakout box, leave ECA connected. Set DVOM on 200-ohm scale and measure resistance between test pin No. 40 and negative post on battery. Also measure resistance between test pin No. 60 and negative post on battery. If readings are greater than 5 ohms, repair cause of resistance in circuit(s). Repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.
3. Checking ECA Ground Insolation. With breakout box installed and ECA connected, turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 46 and 40 and between test pins No. 46 and 60 at breakout box. If both readings are less than 5 ohms, go to next step. If readings are greater than 5 ohms, disconnect ECA connector and inspect for corrosion or damaged pins. Repair if necessary. If fault is still present, replace ECA and repeat QUICK TEST.
4. Continuity of Signal Return Circuit. With breakout box installed and ECA connected, turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 at breakout box and signal return circuit in SELF-TEST connector. If reading is greater than 5 ohms, repair cause of resistance in signal return circuit. Repeat QUICK TEST. If readings is less than 5 ohms, go to next step.
5. Checking KAPWR Circuit. Turn key on, leaving engine off. With ECA connected, set DVOM on 20-volt scale. Measure voltage between battery negative post and test pin No. 1 (KAPWR circuit at EEC power relay). If reading is less than 10.5 volts, check KAPWR and Vehicle Power (VPWR) circuits for shorts to ground. Also check KAPWR circuit from EEC power relay to battery positive post for open circuit. If reading is 10.5 volts or more, go to next step.
6. Ignition Circuit Voltage. Turn key on, leaving engine off. With breakout box and ECA connected, set DVOM on 20-volt scale. Measure voltage between battery negative post and ignition circuit at EEC power relay. If reading is less than 10.5 volts, check for open ignition switch circuits. Repair wiring and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
7. Checking Power Relay Ground Circuit Continuity. Turn key off and wait 10 seconds. With ECA connected and DVOM on 200-ohm scale, measure voltage between battery negative post and EEC relay ground. If reading is greater than 5 ohms, repair wiring in ground circuit. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
8. Checking Power Circuit (VPWR) at Relay. Turn key on, leaving engine off. With ECA connected and DVOM on 20-volt scale, measure voltage between battery negative post and VPWR circuit at EEC power relay. If reading is 10.5 volts or greater, repair open in VPWR circuit. If okay, repair short to ground in VPWR circuit. If reading is less than 10.5 volts, replace EEC power relay. Repeat QUICK TEST.

A3 - REFERENCE VOLTAGE

Note. Perform this test when check of VREF circuit has failed, or directed here by a sensor test or other CIRCUIT TEST.

Reference Voltage Circuits. Scheme 60

1. Checking Battery Power Circuit. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA connected. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 37 and SIGNAL RETURN in SELF-TEST connector. If reading is less than 10.5 volts, go to «A2 - VEHICLE BATTERY»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a2-vehicle-battery) , step 1). If reading is 10.5 volts or more, go to next step.
2. Checking VREF Voltage. With breakout box installed and ECA connected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins No. 26 and 46. If reading is 6 volts or more, go to step 4). If reading is 4 volts or less, go to step 5). If reading is between 4 and 6 volts, go to next step.
3. VREF and Signal Return Continuity. With breakout box installed and ECA disconnected, turn key off. If directed here by a sensor test, ensure that sensor is disconnected. Set DVOM on 200-ohm scale. Measure resistance from test pins No. 26 and 46 to suspect VREF sensor harness connector. If both readings are less than 5 ohms, VREF voltage is okay. Connect all sensors and repeat QUICK TEST. If any reading is 5 ohms or more, repair open circuit in VREF or signal return and then repeat QUICK TEST.
4. Checking For Excess VREF Circuit Voltage. Turn key off and wait 10 seconds. With breakout box installed and ECA disconnected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 26 and battery ground. If reading is less than 0.5 volt, replace ECA and repeat QUICK TEST. If reading is 0.5 volt or more, repair short to battery power in EEC harness. Repeat QUICK TEST. Replace ECA if fault still occurs.
5. Shorted TPS Sensor. Turn key off and wait for 10 seconds. With breakout box installed and ECA connected, disconnect Throttle Position Sensor (TPS) from vehicle harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace TPS and repeat QUICK TEST. If less than 4 volts on models with EVP/PFE sensor, go to next step. If reading is less than 4 volts on all other models, go to step 7).
6. Shorted EVP/PFE Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect EVP/PFE sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace EVP/PFE sensor and repeat QUICK TEST. If reading is less than 4 volts, go to next step.
7. Shorted MAP/BP Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect MAP/BP sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace MAP/BP sensor and repeat QUICK TEST. If reading is less than 4 volts on models without Vane Airflow (VAF) sensor, go to step 9). If reading is less than 4 volts on models with VAF sensor, go to next step.
8. Shorted VAF Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect VAF sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace VAF sensor and repeat QUICK TEST. If reading is less than 4 volts, go to next step.
9. VREF Shorted to Ground. With breakout box installed and ECA disconnected, turn key off and wait 10 seconds. Disconnect TPS, MAP/BP, EVP/PFE, and VAF sensor (if equipped). Set DVOM on 200-ohm scale. Measure resistance between test pin No. 26 and test pins No. 20, 40, 46, and 60. If any resistance is less than 5 ohms, repair short to ground, connect all sensors and repeat QUICK TEST. If original problem still occurs, replace ECA and repeat QUICK TEST. If reading is 5 ohms or more, connect sensors, replace ECA and repeat QUICK TEST.

B1 - VANE AIR TEMPERATURE (VAT) SENSOR

Note. Perform this test only when service code 24, 28, 54, 58, 64, or 68 is received in QUICK TEST. Ambient air temperature must be at least 50°F (10°C) for test results to be valid. Avoid performing test in unusually hot or cold conditions.

VAT Sensor Circuit. Scheme 61

VANE AIR TEMPERATURE (VAT) SENSOR SPECIFICATIONS

1. Code 24 or 28: Check Ambient Temperature. Codes 24 and 28 indicate that the VAT sensor is out of Self-Test range. Correct range for measurement is .35-3.5 volts. Possible causes are; low ambient temperature, Faulty VAF meter, faulty ECA, faulty wiring or connector. Ensure ambient air temperature is at least 50°F (10°C). If not, repeat QUICK TEST. If temperature is at least 50°F (10°C), go to next step.
2. Voltage Reference at TPS. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect Throttle Position Sensor (TPS). Turn key on, leaving engine off. Measure voltage at TPS harness connector between VREF and SIG RTN. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, connect TPS and go to next step.
3. Checking VAT Sensor. Turn key off and wait 10 seconds. Disconnect harness from airflow meter. Set DVOM on 200K-ohm scale. Measure resistance at VAT sensor between VAT and SIG RTN. If resistance is 125 ohms at 240°F (116°C) to 3700 ohms at 50°F (10°C), replace ECA. Connect airflow meter and repeat QUICK TEST. If reading is out of range, repair or replace VAF meter and repeat QUICK TEST.
4. Code 54 or 58: Induce Opposite Code. Service Code 54 and 58 indicate VAT sensor signal is greater than the Self-Test maximum of 3.5 volts (temperature is too low). Possible causes are a lack of continuity between the VAF harness connector and the ECA, a faulty VAF, or a faulty ECA. Turn key off and wait 10 seconds. Disconnect harness from airflow meter. Inspect for and repair any damaged wiring. Install a jumper wire between VAT SIG and SIG RTN at VAF meter connector. Perform KOEO SELF-TEST. If Code 64 or 68 is displayed, replace VAF meter. Remove jumper wire, connect airflow meter, and repeat QUICK TEST. If code 64 or 68 is not displayed, remove jumper wire and go to next step.
5. Checking VAT Signal and Signal Return. Turn key off and wait 10 seconds. With jumper wire removed, leave airflow meter disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 25, at the breakout box and VAT SIG at VAF meter connector. Also measure resistance between test pin No. 46 and signal return at connector. If both readings are less than 5 ohms, replace ECA. Remove breakout box and connect wiring to ECA and airflow meter. Repeat QUICK TEST. If either reading is 5 ohms or more, repair open circuit. Remove breakout box, connect wiring to ECA and airflow meter. Repeat QUICK TEST.
6. Code 64 or 68: Opposite Code Test. Service Code 64 or 68 indicates VAT sensor signal is less than Self-Test minimum value of 0.35 volts. Possible causes of this fault is, VAT signal shorted to signal return, ground, or VREF. A faulty VAF meter or a faulty ECA. Turn key off and wait 10 seconds. Disconnect harness from airflow meter. Inspect for and repair any damaged wiring. Perform KOEO SELF-TEST. If Code 54 or 58 is displayed, replace VAF meter and connect harness. Repeat QUICK TEST. If Code 54 or 58 is not displayed, go to next step.
7. Checking VREF at TPS. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect TPS. Turn key on, leaving engine off. Measure voltage between VREF and SIG RTN at connector. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, connect TPS and go to next step.
8. Checking VAT Signal For Shorts. Turn key off and wait 10 seconds. Leave airflow meter disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 25 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair shorts. Remove breakout box, connect ECA and airflow meter. Repeat QUICK TEST. If all readings are 10K ohms or more, replace ECA. Remove breakout box and connect ECA. Repeat QUICK TEST.
9. Continuous Code 54 or 58. A Continuous Memory Code 54 or 58 indicates that the VAT signal was greater than the Self-Test maximum of 4.5 volts. The code was set during normal driving conditions. Possible causes for this fault: faulty harness or connectors, ECA or VAF meter. Enter KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while tapping VAT sensor lightly and wiggling connector. If fault is indicated, inspect connector and terminals. If connector and terminals are good, replace VAT sensor and repeat QUICK TEST. If a fault is not indicated, go to next step.
10. Wiggle Testing Harness. While in CONTINUOUS MONITOR (WIGGLE) TEST, wiggle and bend EEC-IV harness from VAT sensor to cowl, a small section at a time. Also check harness from cowl to ECA. If fault is indicated, isolate fault and repair as necessary. Repeat QUICK TEST. If no fault is found, go to next step.
11. Inspecting ECA Connectors and Terminals. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for obvious damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay, and you are unable to duplicate fault at this time, clear codes and repeat QUICK TEST.
12. Continuous Codes 64 or 68. A Code 64 or 68 indicates that the VAT signal was less than the Self-Test minimum of 0.3 volt. The code was set during normal driving conditions. Possible causes for this fault: faulty harness or connectors, ECA or VAF meter. Enter KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while tapping VAT sensor lightly and wiggling connector. If fault is indicated, inspect connector and terminals. If connector and terminals are good, replace VAF meter and repeat QUICK TEST. If no fault is indicated, go back and repeat steps 10) and 11).

B2 - AIR CHARGE TEMPERATURE (ACT) SENSOR

Note. Perform this test when Service Code 24, 54, or 64 is displayed during QUICK TESTS or when directed here by other test procedures.

Air Charge Temperature (ACT) Sensor Circuit. Scheme 62

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: cooling system, improper engine oil level, or air cleaner duct problems. Ambient air temperature must be at least 50°F (10°C) for test results to be valid. Avoid performing test in unusually hot or cold conditions.

AIR CHARGE TEMPERATURE (ACT) SENSOR SPECIFICATIONS

1. Code 24: Checking ACT Sensor. Code 24 indicates that the ACT is out of the Self-Test limit range. Correct range for Self-Test measurement is 0.3-3.7 volts. Possible causes for this code are: ACT resistance out of limits or a faulty ECA. For vehicles with ACT sensor mounted in intake manifold, go to next step. If sensor is properly mounted in air cleaner on all other models, go to next step. If sensor is not properly mounted, install ACT sensor properly and repeat QUICK TEST.
2. Checking VREF at TPS. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect TPS. With KOEO, measure voltage between VREF and SIGNAL RETURN at TPS harness connector. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, connect TPS and go to next step.
3. Checking ACT With Engine Off. Start engine and ensure engine reaches normal operating temperature. Turn key off and wait 10 seconds. Disconnect ACT sensor, set DVOM on 200K-ohm scale, and measure ACT sensor resistance. If reading is less than 1100 ohms or more than 58K ohms, check function of heat stove duct valve. If valve is operating correctly, replace ACT sensor. Connect ACT sensor, and repeat QUICK TEST. If reading is between 1100 and 58K ohms, go to next step.
4. Checking ACT With Engine Running. Turn key off. Disconnect ACT sensor harness. Set DVOM on 200K-ohm scale and run engine for 2 minutes. While engine is running, measure ACT sensor resistance. If reading is between 2400 and 29K ohms, replace ECA. Connect ACT harness, and repeat QUICK TEST. If reading is less than 2400 ohms or more than 29K ohms, check function of heat stove duct valve. If valve works properly, replace ACT sensor. Repeat QUICK TEST.
5. Code 54: Generate Code 64. Code 54 indicates the ACT signal is greater than the Self-Test maximum value of 4.6 volts, which could also indicate an open circuit. Possible causes for this code are, open in harness wiring, faulty ACT sensor or faulty ECA. Turn key off and wait 10 seconds. Disconnect ACT sensor harness. Inspect for and repair any damaged wiring. Install a jumper wire between ACT SIGNAL and SIGNAL RETURN at connector. Perform KOEO SELF-TEST. If code 64 is displayed, replace ACT sensor. Remove jumper wire, connect ACT sensor, and repeat QUICK TEST. If code 64 is not displayed, remove jumper wire and go to next step.
6. Continuity Check of ACT Signal and Signal Return. Turn key off and wait 10 seconds. Leave ACT sensor harness disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 25 and ACT SIGNAL at ACT connector, and between test pin No. 46 and SIGNAL RETURN at ACT connector. If both readings are less than 5 ohms, replace ECA and remove breakout box. Connect ECA and ACT sensor, and repeat QUICK TEST. If either reading is 5 ohms or more, repair opens in circuit. Remove breakout box, and connect ECA and ACT sensor. Repeat QUICK TEST.
7. Code 64: Generate Code 54. Code 64 indicates that the ACT signal is less than the Self-Test minimum value of 0.2 volt (grounded circuit). Possible cause for this fault are, faulty ACT sensor, short to ground in harness, faulty ECA. Turn key off and wait 10 seconds. Disconnect ACT sensor. Inspect for and repair any damaged wiring. Perform KOEO SELF-TEST. If code 54 is displayed, replace ACT sensor. Connect harness, and repeat QUICK TEST. If code 54 is not displayed, go to next step.
8. Checking VREF at TPS. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect TPS. Turn key on, leaving engine off. Measure voltage at TPS harness connector between VREF and SIGNAL RETURN at TPS connector (refer to wiring diagram for «B8 - THROTTLE POSITION SENSOR (TPS)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__b8-throttle-position-sensor-tps) . If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, connect TPS and go to next step.
9. Checking ACT Signal for Ground Short. Turn key off and wait 10 seconds. Disconnect harness at ACT sensor. Disconnect ECA 60 pin connector. Inspect for and repair any damaged wiring. Install breakout box and set DVOM on 200K-ohm scale. Measure resistance between test pin No. 25 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair shorts. Remove breakout box, and connect ECA and ACT sensor. Repeat QUICK TEST. If all readings are 10K ohms or more, replace ECA. Remove breakout box, and connect ECA and ACT sensor. Repeat QUICK TEST.
10. Continuous Code 54 Displayed. Code 54 indicates that the ACT signal was greater then the Self-Test maximum value sometime during vehicle operation. Possible causes for this fault are; faulty ACT sensor, open in harness or faulty ECA. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while tapping ACT sensor lightly and wiggling connector. If fault is indicated, inspect connector and terminals. If connector and terminals are good, replace ACT sensor and repeat QUICK TEST. If no fault is indicated, go to next step.
11. Wiggle Testing ACT Harness. While in CONTINUOUS MONITOR (WIGGLE) TEST, wiggle and bend small sections of harness from ACT sensor to firewall. Repeat action from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory codes and repeat QUICK TEST. If no fault is indicated, go to next step.
12. Inspecting Connectors and Terminals. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for obvious damage. If connectors and terminals are not okay, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay, and you are unable to duplicate fault at this time, clear memory codes and repeat QUICK TEST.
13. Continuous Code 64, Check ACT Sensor. Code 64 indicates that the ACT sensor signal was less than the Self-Test minimum value of 0.2 volt sometime during vehicle operation. Possible causes of this fault are; faulty ACT sensor, open in harness or faulty ECA. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while tapping ACT sensor lightly and wiggling connector. If fault is indicated, inspect connector and terminals. If connector and terminals are good, replace ACT sensor and repeat QUICK TEST. If no fault is indicated, repeat step 11).

B3 - MASS AIRFLOW SENSOR (MAF)

Note. Perform this test when Service Code 26, 56, or 66 in displayed in the QUICK TESTS or when directed here by test charts. This test procedure is intended to diagnose only MAF and ECA.

Mass Airflow Sensor (MAF) Circuits. Scheme 63

MAF SIGNAL VOLTAGE

Note. MAF signal voltage is typical for an A/T equipped vehicle at normal operating temperature. Voltage signal may vary do to load and temperature.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: air cleaner element, inlet air duct, or throttle body.

1. KOER Code 26: Out of Range. Code 26 indicates MAF sensor voltage is not in range of .20-1.50 DC volts, and a KOEO or Continuous memory code has been set. Service Code 26 first and then the Continuous memory code (56 or 66). For Code 26, go to next step. For Code 56, go to step 10). For Code 66, go to step 4).
2. Voltage Check at VPWR Circuit. Turn key off and disconnect MAF sensor from vehicle harness. Set DVOM on 20-volt scale. Measure voltage between VPWR circuit at the MAF sensor connector and the negative battery post. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, go to «A2 - VEHICLE BATTERY»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a2-vehicle-battery) , step 1).
3. Checking MAF Sensor Ground. With KOEO and MAF sensor disconnected, set DVOM on 20-volt scale. Measure voltage between VPWR circuit and PWR GND circuit at the MAF sensor connector. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts repair open PWR GND circuit, reconnect MAF and rerun QUICK TEST.
4. Code 66: Continuity of MAF Signal and VPWR Circuits. Code 66 indicates that MAF signal was less than .40 volt during engine operation or KOER SELF-TEST. Possible causes for this fault are: open MAF signal circuit, open VPWR circuit to MAF, open PWR GND circuit to MAF, MAF SIGNAL shorted to ground, Faulty ECA or MAF sensor, air leak before or after MAF sensor, or MAF sensor disconnected. With KOEO and MAF sensor disconnected, disconnect and inspect 60-pin connector. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between MAF SIGNAL at the MAF sensor connector and test pin No. 50 at the breakout box. Measure resistance between VPWR at the MAF sensor connector and test pins No. 37 and 57 at the breakout box. If both resistances are less than 5 ohms, do to next step. If either resistance is greater than 5 ohms, remove breakout box, repair open circuit, reconnect all components and rerun QUICK TEST.
5. Checking MAF Signal Circuit For Shorts. With key off and MAF sensor disconnected, set DVOM on 200K-ohm scale. Disconnect ECA 60-pin connector, inspect connector and terminals. Install breakout box leaving ECA disconnected. Measure resistance between test pin No. 50 and test pins No. 40, 9 and 60, at the breakout box. If all resistances are greater than 10K ohms, go to next step. If resistance in any circuit is below 10K ohms, repair short circuit and rerun QUICK TEST.
6. Checking Continuity of PWR GND Circuit. With key off disconnect MAF sensor. Set DVOM on 200-ohm scale. Measure resistance between PWR GND circuit at MAF sensor connector and battery negative post. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit, reconnect MAF sensor and rerun QUICK TEST. If resistance is 5 ohms or less, go to next step.
7. Checking MAF SIG RTN Circuit Continuity. With key off and MAF sensor disconnected, set DVOM on 200-ohm scale. Disconnect ECA 60 pin connector, inspect pins and install breakout box, leave ECA disconnected. Measure resistance between MAF SIG RTN, at sensor connector, and test pin No. 9 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, remove breakout box. Service open circuit an rerun QUICK TEST.
8. Checking MAF Signal for Short to Ground. With key off, breakout box installed, and ECA connected, disconnect MAF sensor. Set DVOM on 20K-ohm scale. Measure resistance between test pin No. 50 and pins No. 9, 40, and 60 at the breakout box. If all resistances are less than 10K ohms, remove breakout box. Replace ECA and rerun QUICK TEST. If resistances are greater than 10K ohms, go to next step.
9. Checking MAF Output. With key off, install breakout box. Ensure ECA and MAF are connected. Set DVOM on 20-volt scale. Measure voltage between test pin No. 50 and the battery negative post. Start engine. If voltage is .20-1.50 volts replace ECA. If voltage is not .20-1.5, replace MAF sensor.
10. Code 56: Rerun SELF-TEST With MAF Disconnected. With key off, disconnect MAF sensor from vehicle harness. Start engine and allow to idle for one minute. Turn key off. Rerun KOEO SELF-TEST. If Code 66 is present, replace MAF sensor and rerun QUICK TEST. If Code 66 is not present, go to next step.
11. Checking MAF Signal for Short to VPWR. With key off, install breakout box and disconnect MAF sensor and ECA. Set DVOM on 200K-ohm scale. Measure resistance between MAF SIGNAL and VPWR at MAF sensor connector. If resistance is greater than 10K ohms, remove breakout box. Reconnect MAF sensor, replace ECA, and rerun QUICK TEST. If resistance is less than 10K ohms, repair circuit short and rerun QUICK TEST.

B4 - EGR VALVE POSITION SENSOR EGR CONTROL SOLENOID & EGR VENT SOLENOID

Note. Perform this test when Service Code 31, 32, 33, 34, 35, 83, or 84 is displayed during QUICK TESTS or when directed here by other test procedures.

EVP, EGRC & EGRV Solenoid Circuits. Scheme 64

EVP SENSOR SPECIFICATIONS

To prevent replacement of good components, be aware that the following non-EEC related area may be at fault: damaged EGR valve.

1. KOER Code 31. Code 31 indicates that during the KOER SELF-TEST the EVP sensor signal was out of range with the EGR valve in the closed position. Possible causes for this code are a faulty EGRC/EGRV solenoids or a clogged EGRV filter. Turn key off and wait 10 seconds. Disconnect and plug vacuum line at EGR valve. Perform KOER SELF-TEST. If Code 31 is not displayed, reconnect vacuum and go to step 8). If Code 31 is displayed, go to next step. Ignore all other service codes at this time.
2. KOEO Code 31: Checking EVP Resistance With Vacuum Applied. Code 31 displayed during the KOEO SELF-TEST indicates that the EVP sensor signal was out of range with the EGR valve in the closed position. Possible causes for this code are, an open or shorted circuit, faulty EGR valve, faulty EVP sensor, or a faulty ECA. Turn key off and wait 10 seconds. Leave EGR vacuum line disconnected and plugged. Disconnect EVP sensor harness. Set DVOM on 200K-ohm scale and connect vacuum pump to EGR valve. Measure resistance between EVP SIG and VREF at EVP connector while vacuum is slowly increased to 10 in. Hg. If reading is less than 100 ohms or more than 5500 ohms, replace EVP sensor. Connect vacuum line and harness. Repeat QUICK TEST. If reading does not decrease or valve does not hold vacuum, go to step 11). If reading gradually decreases from a maximum of 5500 ohms to a minimum of 100 ohms, go to next step.
3. Checking EVP Signal for Shorts to VREF and SIG RTN. With KOEO, disconnect harness from EVP sensor. Set DVOM on 20-volt scale. Measure voltage between VREF and SIG RTN at EVP connector. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, go to next step.
4. Checking EVP Signal Continuity. Turn key off and wait 10 seconds. Disconnect harness at EVP sensor and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 27 and EVP SIG at EVP connector. If reading is 5 ohms or more, repair open in circuit. Remove breakout box, connect ECA and EVP sensor, and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
5. Checking EVP Signal Circuit for Shorts. Turn key off and disconnect harness at EVP sensor. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 27 and test pins No. 26, 40, 46, and 60. If any reading is less than 10K ohms, repair short circuit. Remove breakout box, connect ECA and EVP sensor. Repeat QUICK TEST. If all readings are 10K ohms or more, go to next step.
6. EVP Sensor and EGR Valve Substitution Test. Turn key off and wait 10 seconds. Connect known good EVP sensor and EGR valve assembly to harness and vacuum lines. Connect ECA to breakout box. Perform KOEO SELF-TEST. If code 31 is displayed, replace ECA. Connect original EVP sensor and EGR valve assembly. Repeat QUICK TEST. If Code 31 is not displayed, go to next step.
7. Testing EVP Sensor. Turn key off and wait 10 seconds. Ensure breakout box is installed and ECA is connected. Install original EVP sensor to known good EGR valve. Connect EVP sensor and perform KOEO SELF-TEST. If Code 31 is displayed, replace EVP sensor and repeat QUICK TEST. If Code 31 is not displayed, service EGR system.
8. Codes 32, 33, or 34 Displayed. Codes 32, 33 or 34 indicate that the EGR valve did not open when instructed to by the ECA. Code 34 indicates the valve would not open. Code 32 indicates the valve is stuck open. Code 33 indicates the valve would not close correctly. Possible causes for these faults are as follows: Faulty vacuum lines. Clogged EGRV filter. Faulty EVP sensor. Faulty EGR valve. Faulty EGRC/EGRV solenoid. Faulty ECA. With key off, disconnect vacuum line at the EGR valve. Connect a vacuum gauge to the vacuum line, leaving the EGR valve disconnected. Observe vacuum gauge while running KOER SELF-TEST. Disregard all other codes produced during this test. If vacuum reading increased from less than one in. Hg to greater than 5 in. Hg and, within 10 seconds, returned to less than one in. Hg go to step 10). If vacuum did not increase, go to next step. If vacuum increased but did not return to less than one in. Hg, check EGRV filter for obstructions, replace filter or solenoid as necessary. Reconnect all vacuum lines and rerun QUICK TEST.
9. Checking Vacuum Supply to EGRC/EGRV Solenoids. With key off, disconnect vacuum source to EGRC/EGRV solenoids. Install a vacuum gauge at the source vacuum line. Start engine and check vacuum. If vacuum is greater than 10 in. Hg, check vacuum line from EGRC/EGRV solenoids to EGR valve for blockage, leaks or damage, replace as necessary. If supply line is okay, replace solenoid assembly and rerun QUICK TEST. If vacuum was below specification, check vacuum source and repair as necessary.
10. Checking EVP Resistance. With key off, disconnect EVP sensor harness. Inspect for and repair any damaged wiring. Set DVOM on 200K-ohm scale. Disconnect vacuum line at EGR valve and connect vacuum pump to valve. Measure resistance of EVP sensor between EVP signal and VREF terminals while increasing vacuum to 10 in. Hg If reading slowly decreases from maximum of 5500 ohms to minimum of 100 ohms, replace ECA. Connect EVP sensor and EGR vacuum line. Repeat QUICK TEST. If reading does not slowly decrease, go to next step.
11. Manual Test of EVP Sensor. With key off, disconnect EVP sensor harness. Remove EVP sensor and vacuum line from EGR valve. Measure resistance of EVP SIG and VREF at the connector while sensor shaft is slowly pushed in and slowly released. If reading increases and decreases smoothly in range of 100-5500 ohms, service or replace EGR valve assembly. Connect EVP sensor and EGR vacuum line. Repeat QUICK TEST. If either reading changes abruptly during range of 100-5500 ohms, replace EVP sensor. Reconnect harness and EGR vacuum line. Repeat QUICK TEST. NOTE: It is normal for EVP sensor total resistance to drop to less than 100 ohms when disconnected from EGR valve. A defective sensor will change resistance suddenly between 5500 and 100 ohms.
12. Code 83 or 84 Displayed: Checking EGRV/EGRC Solenoid Resistance. A Code 83 indicates an EGRC circuit failure. A Code 84 indicates an EGRV circuit failure. Possible causes for these faults are an open or shorted circuit, a faulty EGRC/EGRV solenoid or a faulty ECA. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect EGRC and EGRV solenoids from harness. Inspect for and repair any damaged wiring. Measure resistance of both solenoids. If either reading is less than 30 ohms or more than 70 ohms, replace EGRC/EGRV solenoid assembly. Repeat QUICK TEST. If both readings are between 30 and 70 ohms, reconnect solenoids and go to next step.
13. Checking VPWR at EGRC/EGRV Solenoids. Disconnect EGRC and EGRV solenoids from harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between battery negative terminal and VPWR circuit for both solenoids. If either reading is less than 10.5 volts, repair open circuit and repeat QUICK TEST. If both readings are 10.5 volts or more, go to next step.
14. Continuity Check. Turn key off and wait 10 seconds. Leave EGRC and EGRV solenoids disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 33 and EGRV signal at EGRV solenoid connector. Measure resistance between test pin No. 52 and EGRC signal at EGRC solenoid connector. If either reading is 5 ohms or more, repair open circuit. Remove breakout box, connect ECA solenoids, and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.
15. Checking For Shorts To Ground. Turn key off and wait 10 seconds. Set DVOM on 200K-ohm scale. Install breakout box, leaving ECA disconnected. Disconnect EGRC and EGRV solenoids. Measure resistance between test pin No. 33 and test pins No. 40, 46, and 60. Measure resistance between test pin No. 52 and test pins No. 40, 46, and 60. If readings are less than 10K ohms, repair short to ground. Repeat QUICK TEST. If readings are 10K ohms or more, go to next step.
16. Checking For Shorts To Power. With key off, disconnect EGRC and EGRV solenoids from harness. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 33 and test pins No. 37 and 57. Measure resistance between test pin No. 52 and test pins No. 37 and 57. If any reading is less than 10K ohms, repair short in circuit. Remove breakout box and connect ECA. Repeat QUICK TEST. If all resistances are greater than 10K ohms, replace ECA. Remove breakout box and connect ECA. Repeat QUICK TEST.
17. Code 35: RPM To Low For EGR Test. This code indicates that engine RPM is too low for correct EGR testing. Possible causes for this fault are a faulty ISC system or a faulty ECA. If Code 12 is also displayed go to «D5 - IDLE SPEED CONTROL (AIR BY-PASS)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d5-idle-speed-control-air) , step 1). If Code 12 is not displayed with Code 35, go to next step.
18. Retest at 1500 RPM. Turn key off and wait 10 seconds. Install tachometer. Perform KOER SELF-TEST at 1500 RPM. Ignore all other codes at this time. Record KOER service codes. If code 35 is displayed, replace ECA. Clear codes and repeat QUICK TEST. If code 35 is not displayed, clear codes and repeat QUICK TEST and repair codes as necessary.
19. Continuous Code 31 Displayed. Continuous Code 31 indicates that sometime during vehicle operation the EVP signal was out of the Self-Test range. Possible causes for this fault are an open or shorted circuit or a faulty EVP sensor. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while doing the following: connect vacuum pump to EGR valve. Very slowly apply 6 in. Hg vacuum to EGR valve. Bleed vacuum slowly and lightly tap on EVP sensor. Wiggle EVP sensor connector. If fault is indicated, go to next step. If no fault is indicated, go to step 21).
20. EVP Signal Voltage During Operation. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Stay in KOEO CONTINUOUS MONITOR (WIGGLE) TEST. Connect DVOM between test pins No. 27 and 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Repeat step 19) while watching voltage. If fault occurs below 4.25 volts, disconnect EVP sensor from harness. Inspect for and repair any damaged wiring. If wiring is okay, replace EVP sensor. Clear codes and repeat QUICK TEST. If fault does not occur below 4.25 volts, EGR valve overshoot may have caused Continuous Memory Code 31. Sensor test is complete. Go to next step for harness test.
21. Checking Harness. While in KOEO CONTINUOUS MONITOR (WIGGLE) TEST, bend, shake, and wiggle small sections of EEC-IV harness from sensor to firewall and from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
22. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and terminals for obvious damage. If connector and terminals are damaged, repair as necessary and repeat QUICK TEST. If connector and terminals are okay, fault cannot be duplicated at this time. Continuous Code 31 testing is complete.

B5 - ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Note. Perform this test when directed to by a Code 21, 51, or 61 during QUICK TEST procedure. For purposes of this test, a "warmed up" engine has a coolant temperature of 50-240°F (10-116°C) for KOEO SELF-TEST and 180-240°F (82-116°C) for KOER SELF-TEST. The test procedure will be invalid outside these ranges.

Engine Coolant Temperature (ECT) Sensor Circuit. Scheme 65

ECT SENSOR SPECIFICATIONS

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: coolant or oil level, blocked or obstructed airflow, engine not at normal operating temperature, or cooling fan.

1. Code 21: Check Engine Temperature. Code 21 indicates that the ECT is out of the 0.3-3.5 volt Self-Test range. Possible causes for this fault are ECT resistance out of limits or a faulty ECA. If engine will not start, go to step 4). Start engine and run at 2000 RPM for 2 minutes. Check that upper radiator hose is hot and pressurized. Repeat QUICK TEST before continuing. If vehicle stalls, DO NOT service code 21 at this time, go directly to DIAGNOSIS BY SYMPTOM TEST. If code 21 is not displayed, service other codes as necessary (if displayed). If code 21 appears, go to next step.
2. Checking for VREF at TPS. Refer to wiring diagram in «B8 - THROTTLE POSITION SENSOR (TPS)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__b8-throttle-position-sensor-tps) . Turn key off and wait 10 seconds. Disconnect TPS. Set DVOM on 20-volt scale. With KOEO measure voltage at TPS harness connector between VREF and SIGNAL RETURN. If voltage is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If voltage is between 4 and 6 volts, reconnect TPS and go to next step.
3. ECT Sensor Resistance. Ensure engine is fully warmed up for this step. Turn key off and wait 10 seconds. Disconnect wiring harness at ECT sensor. Set DVOM on 200K-ohm scale and measure resistance of ECT sensor. If reading is 1300-7700 ohms at engine coolant temperature of 140-240°F (60-116°C) with engine off and 1550-4550 ohms at 180-230°F (82-110°C) with engine running, replace ECA, connect ECT sensor and repeat QUICK TEST. If readings are not correct for coolant temperature, replace ECT sensor, connect harness, and repeat QUICK TEST.
4. Checking ECT Resistance: No Start Condition. With key off, disconnect ECT sensor and set DVOM on 200K-ohm scale. Measure resistance of ECT sensor. If resistance is within specifications, DO NOT service Code 21 at this time. Go to «A1 - NO START»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) . If resistance is not within specification, replace ECT sensor.
5. Code 51: Generate Code 61. Code 51 indicates that the ECT signal was greater than the Self-Test maximum value of 4.6 volts (open circuit). Possible causes for this fault are a faulty ECT sensor, open circuit or faulty ECA. Turn key off and wait 10 seconds. Disconnect ECT sensor at wiring harness and inspect wiring for damage or corrosion. Connect a jumper wire between ECT SIGNAL and SIGNAL RETURN terminals in sensor harness connector. Repeat KOEO SELF-TEST. If Code 61 is displayed, replace ECT sensor and remove jumper wire. Reconnect harness to ECT sensor and repeat QUICK TEST. If Code 61 is not displayed, remove jumper wire and go to next step.
6. ECT Signal and Return Continuity Check. Turn key off and wait 10 seconds. With harness disconnected at ECT sensor and jumper removed from harness connector, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between ECT SIGNAL at ECT connector and test pin No. 7. Measure resistance between SIGNAL RETURN at ECT connector and test pin No. 46. If both readings are less than 5 ohms, replace ECA. Remove breakout box and connect ECA and ECT sensor. Repeat QUICK TEST. If either reading is 5 ohms or more, repair open circuits. Remove breakout box, and connect ECA and ECT sensor. Repeat QUICK TEST.
7. Code 61: Generate Code 51. Code 61 indicates that the ECT signal is less than the 0.2 volt Self-Test minimum value (grounded circuit). Possible causes of this fault are a faulty ECT, grounded circuit or faulty ECA. Turn key off and wait 10 seconds. Disconnect ECT sensor and inspect connector for damage or corrosion. Repair wiring and repeat KOEO SELF-TEST. If Code 51 is displayed, replace ECT sensor, connect sensor, and repeat QUICK TEST. If Code 51 is not displayed, go to next step.
8. Checking VREF at TPS. Refer to wiring diagram in «B8 - THROTTLE POSITION SENSOR (TPS)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__b8-throttle-position-sensor-tps) . Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect TPS. Turn key on, leaving engine off. Measure voltage between VREF and SIGNAL RETURN at TPS connector. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If voltage is between 4 and 6 volts, connect TPS and go to next step.
9. Checking ECT Signal for Short to Ground. Turn key off and wait 10 seconds. Disconnect harness from ECT sensor. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 7 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short circuits. Remove breakout box, connect ECA and ECT sensor, and repeat QUICK TEST. If all readings are 10K ohms or more, replace ECA. Remove breakout box, connect ECA and ECT sensor. Repeat QUICK TEST.
10. Continuous Code 51: Check ECT Sensor. Code 51 indicates that the ECT signal was greater than the Self-Test maximum voltage of 4.6 volts sometime during vehicle operation. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while tapping ECT sensor and wiggling ECT connector. If fault is indicated, disconnect and inspect ECT connector and terminals. If connector and terminals are okay, replace ECT sensor. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
11. Checking Harness. While in KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault as you bend, shake or wiggle EEC-IV harness. Start at sensor connector and work toward firewall. Also test harness from firewall to ECA in same manner. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes and repeat QUICK TEST. If fault is not indicated, go to next step.
12. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Go to next step.
13. Continuous Code 61: Check ECT Sensor. Code 61 indicates that the ECT signal was less than the 0.2 volt Self-Test minimum value (grounded circuit) sometime during vehicle operation. Possible causes of this fault are; faulty ECT, grounded circuit or faulty ECA. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while tapping ECT sensor and wiggling ECT connector. If fault is indicated, disconnect and inspect ECT connector and terminals. If connector and terminals are okay, replace ECT sensor and repeat QUICK TEST. If no fault is indicated, repeat steps 10) and 11).

B6 - MANIFOLD ABSOLUTE PRESS. (MAP)/BAROMETRIC PRESS. (BP) SENSOR

Note. This test should be performed when Service Code 22 or 72 is displayed in QUICK TEST procedures, or when directed here by D20 - INTAKE AIR CONTROL VALVE (IAC) or other symptom. Barometric pressure sensor output is digital and must be measured with an oscilloscope or MAP/BP tester.

MAP/BP Tester Hook-Up. Scheme 66

MAP SENSOR SPECIFICATIONS

MAP/BP SENSOR SPECIFICATIONS

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: unusually high/low atmospheric barometer reading, kinked or blocked vacuum lines, or engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.).

1. KOEO Code 22. Code 22 indicates that the MAP/BP sensor is out of Self-Test voltage range (1.4-1.6 volts). Possible causes of this code are: MAP/BP signal circuit open between sensor and ECA. MAP/BP signal circuit shorted to VREF, SIG RTN or ground. Faulty MAP/BP sensor. High atmospheric pressure. Faulty ECA. VREF circuit open at sensor. SIG RTN open at sensor. Turn key off. Disconnect MAP/BP sensor from harness. Connect MAP/BP tester between wiring harness and MAP/BP sensor. Connect banana plugs of tester into DVOM and set DVOM on 20-volt scale. See MAP/BP TESTER HOOK-UP illustration. Go to next step.
2. Checking Power to Sensor. With MAP/BP tester connected, turn key on. If only Green light on tester is lit, VREF is correct, go to step 4). If "LESS THAN 4 VOLTS" Red light or no lights come on, VREF is too low. If "MORE THAN 6 VOLTS" Red light comes on, VREF is too high. If VREF is too high or too low, go to next step.
3. VREF Testing. With MAP/BP tester connected, turn key on. Disconnect MAP/BP sensor and repeat step 2). If only Green light comes on, VREF is correct. Replace MAP/BP sensor and repeat QUICK TEST. If "LESS THAN 4 VOLTS" Red light or no lights come on, VREF is too low. If "MORE THAN 6 VOLTS" Red light comes on, VREF is too high. If VREF is too high or too low, remove MAP/BP tester, connect sensor, then go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1).
4. Tester Output Reading. With MAP/BP tester connected and key on, measure sensor output voltage. If voltage output is in correct range for altitude of vehicle being tested, remove MAP/BP tester and go to next step. If output reading is outside range, remove MAP/BP tester and go to step 6). NOTE: Measure several known good MAP/BP sensors on available vehicles. Average voltage reading will be typical for your location on date of testing. MAP SENSOR VOLTAGE OUTPUT Elevation (Ft.) Volts 0 1.55-1.63 1000 1.52-1.60 2000 1.49-1.57 3000 1.46-1.54 4000 1.43-1.51 5000 1.40-1.48 6000 1.37-1.45 7000 1.35-1.43
5. Checking Signal Continuity. Turn key off and wait 10 seconds. Disconnect MAP/BP sensor from harness. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between MAP/BP signal at sensor connector and test pin No. 45. If reading is less than 5 ohms, replace ECA. Connect ECA and MAP/BP sensor and repeat QUICK TEST. If reading is 5 ohms or higher, repair opens in wiring. Remove breakout box, connect ECA and MAP/BP sensor. Repeat QUICK TEST.
6. Checking MAP/BP Signal For Shorts. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect harness at MAP/BP sensor. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 45 and test pins No. 26, 46, 40, and 60. If any reading is less than 10K ohms, repair shorts in wiring. Remove breakout box and connect ECA and MAP/BP sensor. Repeat QUICK TEST. If all readings are 10K ohms or more, replace MAP/BP sensor. Remove breakout box and connect all wiring. Repeat QUICK TEST.
7. Code 22: Check for EGR Codes. Check to see if Service Codes 31, 32, 33, 34 or 35 are present. If so, go to KOER SELF-TEST table and perform appropriate CIRCUIT TEST. If not, go to next step.
8. Checking MAP Sensor. Turn key off and wait 10 seconds. Disconnect vacuum hose from MAP sensor. Connect vacuum pump to MAP sensor and apply 18 in. Hg vacuum to sensor. If sensor does not hold vacuum, replace sensor, connect vacuum line and repeat QUICK TEST. If MAP sensor does hold vacuum, release vacuum and go to next step.
9. Eliminating Code 22. Turn key off and wait 10 seconds. Plug vacuum hose going to MAP sensor. Start engine and run at 1400-1600 RPM. Slowly apply 15 in. Hg. vacuum to MAP sensor. With engine under these operating conditions, perform KOER SELF-TEST. Check for Code 22, disregard any other codes at this time. If Code 22 is still present, replace MAP sensor. If Code 22 is no longer displayed, inspect vacuum hose going to MAP sensor. If okay, service other codes at this time. If there are none, check engine for cause of low vacuum.
10. Code 72: Check Vacuum Lines. Code 72 indicates that MAP sensor output did not change enough during dynamic response ("Goose") test. Possible causes for this code are an incorrect MAP sensor vacuum line routing or a faulty MAP sensor. With key on, check vacuum lines for correct routing. Check for disconnections, kinks or blockage. Repair vacuum lines as necessary. If vacuum lines are okay, go to next step.
11. Checking MAP Sensor. Test MAP sensor as described in step 8). If MAP sensor does hold vacuum, release vacuum and go to next step.
12. Checking Vacuum Supply During "Goose" Test. Turn key off, wait 10 seconds. Use a "T" fitting to install a vacuum gauge in the intake manifold MAP sensor supply line. Run the KOER SELF-TEST while observing the vacuum gauge. If vacuum decreased by more than 10 in. Hg during dynamic response ("Goose") test, remove gauge, replace MAP sensor and rerun QUICK TEST. If vacuum did not decrease by 10 in. Hg or more, repair engine mechanical components as necessary to increase engine vacuum.
13. Continuous Code 22: Operating MAP/BP Sensor. Continuous Code 22 indicates the MAP/BP sensor was out of Self-Test range (1.4-1.6 volts) during normal driving conditions. Possible causes for this code are a faulty MAP/BP sensor, faulty wiring harness or connectors, and unusually high or low barometric pressure. In KOEO CONTINUOUS MONITOR TEST mode, observe test equipment while performing the following: Connect a vacuum pump to the MAP/BP sensor. Slowly apply 25 in. Hg vacuum to sensor. Slowly bleed off vacuum from sensor. Lightly tap on sensor (to simulate road shock). "Wiggle" sensor connector. If a fault is indicated disconnect sensor and inspect connectors. Repair as necessary. If connectors are okay, replace MAP/BP sensor. If a fault is not indicated, go to next step.
14. Checking Harness. Stay in KOEO CONTINUOUS MONITOR (WIGGLE) TEST. Observe VOM or diagnostic tester for indication of fault while shaking, bending or wiggling small sections of harness from sensor connector to firewall. Check harness from firewall to ECA in same manner. If fault is indicated, isolate fault in harness and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
15. Checking ECA Connector and Harness. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are not okay, repair as necessary. Repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Code 22 testing is complete.

B7 - KNOCK SENSOR (KS)

Note. Perform this test when Service Code 25 is received during QUICK TEST procedure or you are directed here by other diagnostic tests. Use DYNAMIC RESPONSE CHECK as specified in steps 1) and 6). There is no need to perform WOT during this test. For additional information see QUICK TEST DIAGNOSTIC AIDS, DYNAMIC RESPONSE CHECK in front of this article.

Knock (Detonation) Sensor Circuit. Scheme 67

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuel quality, engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.) and spark timing.

1. Code 25: Generate Knock Manually. Code 25 indicates that the Knock Sensor (KS) signal was not sensed during the dynamic response ("Goose") test after the engine ID code in the KOER SELF-TEST. Possible causes for this fault are a faulty KS, open or shorted harness or faulty ECA. Have 4 oz. hammer ready. Ensure engine is at normal operating temperature. Perform KOER SELF-TEST. When DYNAMIC RESPONSE CHECK signal appears, lightly tap above knock sensor with 4 oz. hammer. DO NOT "Goose" throttle. After 15 seconds, check for Code 25. Ignore all other codes at this time. If code 25 is displayed, go to next step. If Code 25 is not displayed, knock system is okay. Repeat KOER SELF-TEST and service other codes.
2. Circuit Voltage Check. Turn key off and wait 10 seconds. Disconnect knock sensor. Inspect for and repair any damaged wiring. Set DVOM on 20-volt scale. With KOEO measure voltage at knock sensor connector between KS and SIGNAL RETURN. If reading is greater than 4 volts, go to step 5). If voltage is 1-4 volts, go to step 6). If reading is less than one volt, go to next step.
3. Check Continuity of KS and Signal Return Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and knock sensor disconnected. With DVOM on 200-ohm scale, measure resistance between SIGNAL RETURN at sensor harness connector and test pin No. 46, and between knock sensor connector KS signal and test pin No. 23. If either reading is 5 ohms or more, service open circuit and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.
4. Checking KS Circuit for Short to Ground. Turn key off and wait 10 seconds. With breakout box installed, ECA and knock sensor disconnected, set DVOM on 200K-ohm scale. Measure resistance between knock sensor connector KS signal and test pins No. 40, 46 and 60. If all readings are 10K ohms or more, go to step 6). If any reading is less than 10K ohms, repair shorts in harness and repeat QUICK TEST.
5. Checking KS Circuit for Short to Power. Turn key off and wait 10 seconds. With breakout box installed, ECA and sensor disconnected, set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between test pins No. 23 and 40. If reading is 0.5 volt or more, repair knock sensor harness short to power, and repeat QUICK TEST. If reading is less than 0.5 volt, go to next step.
6. Test ECA By Sensor Substitution. Turn key off and wait 10 seconds. Remove breakout box and connect ECA. Connect substitute knock sensor into harness but DO NOT install in engine. Substitute should be a known good unit with the same part number. Ensure engine is at normal operating temperature. Perform KOER SELF-TEST. When DYNAMIC RESPONSE CHECK signal appears, lightly tap knock sensor with 4 oz. hammer. DO NOT "Goose" throttle. If Code 25 is displayed replace ECA, reconnect original knock sensor and rerun QUICK TEST. Ignore all other codes at this time. If Code 25 does not appear, install new knock sensor and repeat QUICK TEST.

B8 - THROTTLE POSITION SENSOR (TPS)

Note. Perform this test when Service Code 23, 53, 63, or 73 is displayed during QUICK TEST.

TPS Electrical Circuit & Specification Table. Scheme 68

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: idle speed/throttle stop adjustment, binding throttle shaft/linkage or cruise control linkage.

1. Code 23. Code 23 indicates that the TPS rotational setting may be out of the Self-Test range. See TPS SPECIFICATION TABLE. If KOEO SELF-TEST Code 68 or KOER SELF-TEST Codes 31, 41, or 58 are displayed, service these codes first. Disregard Code 23 at this time. If these codes have been serviced or are not displayed, go to next step.
2. Check for Stuck Throttle Plate. Inspect throttle body and linkage for binding or sticking. Ensure linkage is set with throttle in closed position. If throttle plate or linkage is binding, check for binding throttle or cruise control linkage, vacuum line or harness interference, etc. Repair any problem and repeat QUICK TEST. If no mechanical problem is found, go to next step.
3. Code 53: Generate Code 63. Code 53 indicates that TPS signal is greater than Self-Test maximum value. Turn key off and wait 10 seconds. Disconnect TPS from harness at throttle body. Inspect for and repair any damaged wiring. Perform KOEO SELF-TEST. Check for Code 63. Ignore all other codes at this time. If Code 63 is not displayed, go to step 5). If Code 63 is displayed, go to next step.
4. Check VREF to Signal Return. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect TPS from harness. Inspect for and repair any damaged wiring. With KOEO, measure voltage at TPS connector between VREF and SIG RTN If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, replace TPS and repeat QUICK TEST.
5. Checking TP Signal For Short to Power. Turn key off and wait 10 seconds. Disconnect TPS from harness. Set DVOM on 200K-ohm scale. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Measure resistance between test pin No. 47 and test pins No. 26 and 57. If either reading is less than 10K ohms, repair short in harness and repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA and repeat QUICK TEST.
6. Code 63: Generate Code 53. Code 63 indicates that TP signal is less than minimum Self-Test value. Turn key off and wait 10 seconds. Disconnect TPS from harness. Install a jumper wire between VREF and TP signal at connector. Perform KOEO SELF-TEST. Check for Codes 53 or 23. Ignore all other codes at this time. If no codes are displayed, immediately remove jumper wire, and go to step 9). If either Code 53 or 23 is displayed, replace TPS and repeat QUICK TEST. If neither Code 53 or 23 is displayed, go to next step.
7. Code 63: Check Voltage VREF to SIG RTN. Turn key off and wait 10 seconds. Disconnect TPS from harness. Inspect for and repair any damaged wiring. Set DVOM on 20-volt scale. With KOEO, measure voltage between VREF and SIG RTN at TP connector. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, go to next step.
8. Checking TPS Circuit Continuity. Turn key off and wait 10 seconds. Leave TPS disconnected. Set DVOM on 200-ohm scale and disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Measure resistance between TP signal at connector and test pin No. 47. If reading is 5 ohms or more, repair faulty circuit. Remove breakout box, connect ECA and TPS, and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
9. Checking Resistance Between Ground and Signal Return. Turn key off and wait 10 seconds. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and set DVOM on 200K-ohm scale. Measure resistance at connector between TPS signal and ground, and between TPS signal and test pin No. 46. If either reading is less than 10K ohms, repair short circuit and repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA. Remove breakout box, connect TPS, and repeat QUICK TEST. NOTE: Code 73 in step 10) indicates that TPS did not exceed 25% of its rotation during DYNAMIC RESPONSE ("Goose") CHECK. For additional information see KOER SELF-TEST, DYNAMIC RESPONSE CHECK in this article.
10. Code 73: TPS Movement. Turn key off. Install breakout box and connect ECA. Set DVOM on 20-volt scale. Connect DVOM to test pins No. 46 and 47. Perform KOER SELF-TEST. Verify that DVOM reading exceeds 3.5 volts during "Goose" check. If reading exceeds 3.5 volts, replace ECA. Clear codes and repeat QUICK TEST. If reading does not exceed 3.5 volts, ensure TPS is correctly installed and adjusted. If okay, replace TPS, clear codes and repeat QUICK TEST.
11. Code 53: TPS Movement. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position, lightly tap TPS and wiggle connector. If no fault is indicated, go to step 13). If fault is indicated, go to next step.
12. TPS Voltage Measurement. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA connected. Stay in KOEO CONTINUOUS MONITOR (WIGGLE) TEST as in previous step 11). Connect DVOM between test pins No. 47 and 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Observe DVOM and repeat step 11). If fault occurs at less than 4.25 volts, inspect TPS connectors and terminals. If okay, replace TPS, clear codes and repeat QUICK TEST. If fault does not occur at less than 4.25 volts, TPS over-travel may have caused Continuous Code 53. TPS is okay, go to next step to check harness.
13. Checking Harness. While in KOEO CONTINUOUS MONITOR (WIGGLE) TEST, shake, bend and wiggle small sections of EEC-IV harness from TPS to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
14. Checking Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary. Clear codes and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Code 53 testing is complete.
15. Continuous Code 63 Displayed. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position and lightly tap TPS and wiggle connector. If fault is indicated, disconnect TPS. Inspect connectors and terminals. If connectors and terminals are okay, replace TPS. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
16. Harness Test. While in KOEO CONTINUOUS MONITOR (WIGGLE) TEST, shake, bend and wiggle small sections of EEC-IV harness from TPS sensor to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
17. ECA Connector Test. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary. Clear codes and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Code 63 testing is complete.

B9 - VANE AIRFLOW (VAF) SENSOR

Note. Perform this test when Service Code 26, 56, 66, or 76 is displayed during QUICK TESTS or when directed here by other test procedures.

VAF Sensor Circuit. Scheme 69

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: check for air leaks between VAF sensor and throttle body. Check for vacuum leaks. Check engine sealing at PCV, CANP, valve cover(s), and at dipstick seal.

Scheme 70

1. Code 26: VAF Movement Obstructed. Code 26 indicates VAF sensor signal is out of Self-Test range. Self-Test range is 0.17-0.50 volts with KOEO or 1.10-1.70 volts with KOER. Possible causes for this fault are a faulty vane meter, faulty ECA or wiring harness. Turn key off and wait 10 seconds. Remove air filter and check for contamination (oil residue or foreign matter). If Code 26 appears in KOEO SELF-TEST, replace or service VAF sensor. Install air cleaner and repeat QUICK TEST. If Code 26 is not displayed, go to next step.
2. Checking VAF Sensor. With key off, check for air leaks allowing unmetered air into system between VAF sensor and throttle body. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA to box. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Place new, unsharpened pencil through air inlet opening of VAF sensor. See VAF SENSOR CHECK illustration. Measure voltage between test pins No. 43 and 46. If reading is between 2.8 and 3.7 volts, VAF sensor is okay. Code 26 may be caused by incorrect engine speed or vacuum leak. Go to «D4 - CANISTER PURGE (CANP)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d4-canister-purge-canp), step 11) and ensure Code 26 has not been caused by canister purge function. Repair problem, remove breakout box and repeat QUICK TEST. If reading is not between 2.8 and 3.7 volts, inspect VAF connector pins and repeat QUICK TEST. Replace VAF if problem still exists. (Scheme 70): VAF Sensor Check
3. Code 56: Generate Code 66. Code 56 indicates that the VAF signal is greater than the Self-Test maximum of 4.89 volts. Possible causes for this fault are a faulty VAF, faulty ECA, VAF SIG circuit shorted to power or a faulty wiring harness. Turn key off and wait 10 seconds. Disconnect harness from VAF. Inspect for and repair any damaged wiring. Rerun KOEO SELF-TEST. If Code 66 is not displayed, go to step 5). If Code 66 is displayed, go to next step.
4. Checking VAF Signal Return Voltage. Turn key off and wait 10 seconds. Leave harness disconnected from VAF sensor. Set DVOM on 20-volt scale. With KOEO measure voltage at VAF harness connector between VREF and SIG RTN. If reading is between 4 and 6 volts, replace VAF sensor. Connect harness and repeat QUICK TEST. If reading is less than 4 or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage), step 1).
5. Checking VAF Signal For Shorts to Power. Turn key off and wait 10 seconds. Leave VAF sensor disconnected. Disconnect 60-pin connector from ECA. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 43 and test pins No. 26 and 57. If either reading is less than 10K ohms, repair short in wiring. Remove breakout box. Connect ECA and VAF sensor and then repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA. Remove breakout box. Connect ECA and VAF sensor. Repeat QUICK TEST.
6. KOEO Code 66: Generate Code 56. Code 66 indicates that the VAF signal is less than the Self-Test minimum of 0.17 volt during the KOEO SELF-TEST. Possible causes for this fault are a faulty VAF, faulty ECA, VAF SIG circuit shorted to ground or a faulty wiring harness. Turn key off and wait 10 seconds. Disconnect harness from VAF sensor. Install jumper wire between VREF and VAF SIG at connector. Perform KOEO SELF-TEST. Ignore all codes except VAF codes at this time. If no codes are displayed, immediately remove jumper wire and go directly to step 9). If Code 56 is displayed, replace VAF sensor. Remove jumper wire, connect VAF sensor, and repeat QUICK TEST. If Code 56 is not displayed, remove jumper wire and go to next step.
7. Checking VREF at VAF Sensor. Turn key off and wait 10 seconds. Leave VAF sensor disconnected. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between VREF and SIG RTN return at VAF sensor harness connector. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage), step 1). If reading is between 4 and 6 volts, go to next step.
8. Checking Continuity of VAF SIG. With key off and VAF sensor disconnected, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between VAF SIG at sensor connector and test pin No. 43. If reading is 5 ohms or more, repair open circuit. Remove breakout box, connect ECA and VAF sensor. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
9. Checking VAF Signal For Short to Ground. Turn key off and wait 10 seconds. Leave ECA and VAF sensor disconnected. Set DVOM on 200K-ohm scale. Measure resistance between VAF SIG and SIG RTN at harness connector. Also measure resistance between VAF SIG and negative battery terminal. If either reading is less than 10K ohms, repair shorts. Connect VAF sensor and repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA. Remove breakout box, and connect ECA and VAF sensor. Repeat QUICK TEST. NOTE: A quick "Goose" test may not be sufficient to pass step 10). Be sure to move throttle to WOT. For additional information, see KOER SELF-TEST, DYNAMIC RESPONSE CHECK in front of this article.
10. KOER Code 76 Displayed. Code 76 indicates that VAF output voltage did not change during the WOT "Goose" test. Possible causes for this fault are an obstructed air cleaner or duct, a faulty vane meter or a faulty ECA. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box and connect ECA. Set DVOM on 20-volt scale. Connect DVOM to test pin No. 43 and 46. Perform KOER SELF-TEST while observing DVOM. As soon as DYNAMIC RESPONSE CHECK signal is displayed, perform WOT. Reading on DVOM should increase by more than 2 volts from the reading before WOT. Observe service codes at end of test. If reading increased by more than 2 volts, go to next step. If not, check air cleaner duct for obstructions. If okay, replace VAF sensor.
11. Checking Service Codes. Observe KOEO SELF-TEST service codes at end of step 10). If Code 76 is still displayed, replace ECA. Remove breakout box and repeat QUICK TEST. If Code 76 is not displayed, VAF sensor is okay. Service other codes as necessary.
12. Continuous Memory Code 56. Code 56 indicates that the VAF sensor signal was greater than the Self-Test maximum value of 4.89 volts. The code was set during normal driving conditions. Possible causes for this fault are a faulty vane meter, Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while lightly tapping VAF sensor and wiggling connector. If a fault is indicated, disconnect connector. Inspect connector and terminals for damage. If connector and terminals are okay, replace VAF sensor and repeat QUICK TEST. If no fault is indicated, go to next step.
13. Checking Harness. While in KOEO CONTINUOUS MONITOR (WIGGLE) TEST, shake, bend and wiggle small sections of EEC-IV harness from VAF sensor connector to firewall and from firewall to ECA. If fault is indicated, isolate and repair damaged wiring. Repeat QUICK TEST. If no fault is indicated, go to next step.
14. Checking Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Clear codes and rerun QUICK TEST.
15. KOER Code 66. KOER Code 66 indicates that the VAF sensor signal was less than the Self-Test minimum of 0.17 volts. The code was set during normal driving conditions. Possible causes for this fault are a faulty VAF harness or connector, faulty VAF sensor, or a fault ECA. Enter KOEO Continuous Monitor mode. Observe DVOM while tapping lightly on VAF sensor to simulate road shock. Wiggle VAF connector. If a fault is indicated repair wiring or connectors as necessary. If connectors and wiring are okay, replace VAF sensor. If a fault is not indicated, check harness and connectors as described in steps 13) and 14).

B10 - PRESSURE FEEDBACK EGR VALVE & EGR VACUM REGULATOR SOLENOID

Note. Perform this test when Service Code 31, 32, 33, 34, 35, or 84 is displayed during QUICK TESTS or when directed here by other test procedures.

Pressure Feedback EGR (PFE) & EGR Valve Regulator (EVR) Circuits. Scheme 71

PFE SENSOR SPECIFICATIONS

1. Code 31: Generate Code 35. Code 31 indicates the PFE sensor signal is less than the Self-Test minimum of 0.2 volt. Turn key off. Disconnect PFE harness at sensor. Install a jumper wire between VREF and PFE SIGNAL at sensor connector. Perform KOEO SELF-TEST. Check for Code 35. Ignore all other codes at this time. If no codes are displayed, immediately remove jumper wire and go directly to step 4). If Code 35 is displayed, remove jumper wire and replace PFE sensor. Repeat QUICK TEST. If Code 35 is not displayed, go to next step.
2. Measuring VREF to SIG RTN Voltage. With key off and PFE harness disconnected, set DVOM on 20-volt scale. With KOEO, measure voltage at PFE connector between VREF and SIG RTN. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, go to next step.
3. PFE Signal Continuity. With key off and PFE harness disconnected, set DVOM on 200-ohm scale. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Measure resistance between PFE SIGNAL at connector and test pin No. 27. If reading is 5 ohms or more, repair faulty circuit. Connect PFE sensor and remove breakout box. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
4. PFE Signal Circuit Resistance. With key off and PFE harness disconnected, install breakout box leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between ground and PFE signal at connector. Measure resistance between PFE signal at connector and test pin No. 46. If either reading is less than 10K ohms, repair short circuit. Connect PFE and remove breakout box. Repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA. Connect PFE and remove breakout box. Repeat QUICK TEST.
5. Code 35: Generate Code 31. Code 35 indicates the PFE sensor signal is greater than the Self-Test maximum of 4.8 volts. Turn key off and disconnect PFE harness at sensor. Inspect for and repair any damaged wiring. Perform KOEO SELF-TEST. Check for Code 31. Ignore all other codes at this time. If Code 31 is not displayed, go to step 7). If Code 31 is displayed, go to next step.
6. Measuring VREF to SIG RTN Voltage. Refer to wiring diagram. With key off and PFE harness disconnected, set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage at PFE connector between VREF and SIG RTN. If reading is between 4 and 6 volts, replace PFE sensor. Repeat QUICK TEST. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1).
7. Checking PFE Circuit For Shorts. With key off and PFE harness disconnected, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 27 and test pins No. 26, 37 and 57. If either reading is less than 10K ohms, repair short. Connect PFE and remove breakout box. Repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA. Connect PFE and remove breakout box. Repeat QUICK TEST.
8. Code 34: PFE Sensor Out Of Range. Code 34 indicates that PFE sensor is out of Self-Test range of 2.6-4.2 volts and that PFE sensor is probably faulty. The PFE system can detect lack of pressure in exhaust system. An efficient garage exhaust ventilation system, installed during KOEO SELF-TEST may cause PFE sensor to generate Code 34. Remove exhaust ventilation system and retest. If Code 34 is not displayed, service other codes displayed during KOEO SELF-TEST. If none are displayed, continue with QUICK TEST. If Code 34 is displayed, go to next step.
9. Inspecting Supply to PFE Sensor. Remove pressure feed tube from PFE sensor. Inspect complete tube, including PFE inlet for blockage. If blockage is found, repair as necessary. Repeat QUICK TEST. If no blockage is found, go to next step.
10. Measuring VREF to SIG RTN Voltage. Turn key off and disconnect PFE sensor. Inspect for and repair any damaged wiring. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage at PFE connector between VREF and SIG RTN. If reading is between 4 and 6 volts, replace PFE sensor. Repeat QUICK TEST. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1).
11. Code 84: Measure EVR Solenoid Resistance. Code 84 indicates a failure in EVR solenoid circuit. Turn key off. Set DVOM on 200-ohm scale. Disconnect EVR solenoid connector and measure solenoid resistance. If reading is less than 30 ohms or more than 70 ohms, replace EVR solenoid assembly. Repeat QUICK TEST. If reading is between 30 and 70 ohms, go to next step.
12. Checking VPWR at EVR Solenoid. With KOEO and EVR solenoid disconnected from harness, set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between negative battery terminal and VPWR circuit at EVR solenoid connector. If reading is less than 10.5 volts, repair VPWR open circuit. Repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
13. Checking Continuity of EVR Circuit. Turn key off and disconnect EVR solenoid from harness. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 33 at the breakout box and EVR signal at the EVR solenoid harness. If reading is 5 ohms or more, repair open circuit. Connect EVR solenoid and remove breakout box. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
14. Checking EVR Circuit For Ground Shorts. Turn key off. Install breakout box, leaving ECA disconnected. Disconnect EVR solenoid. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 33 and test pins No. 37, 57, 40, and 60 at the breakout box. If any reading is less than 10K ohms, repair short circuit. Remove breakout box. Connect ECA and EVR solenoid. Repeat QUICK TEST. If code is repeated, replace ECA. If all readings are 10K ohms or more, replace ECA. Remove breakout box. Connect ECA and EVR solenoid. Repeat QUICK TEST.
15. Code 32: Verify Engine Running Codes. Code 32 indicates EGR valve is not fully seated. Possible causes for this fault are obstructed vacuum line, contaminated EVR filter, faulty EGR valve or faulty EVR solenoid. The PFE system can detect a lack of pressure in exhaust system. An efficient garage exhaust ventilation system, installed during KOER SELF-TEST may cause PFE sensor to generate Code 32. Temporarily remove exhaust ventilation system and retest. If Code 32 is not displayed, service other codes displayed during KOER SELF-TEST. If none, continue with QUICK TEST. If Code 32 is displayed, go to next step.
16. Code 31: Separating EVR From PFE. Code 31 indicates PFE sensor signal is less than Self-Test minimum. Turn key off. Disconnect and plug EGR valve vacuum hose. Perform KOER SELF-TEST. If Codes 31 or 32 are present, go to next step. If not, go to step 18).
17. Checking PFE Supply Tube for Blockage. With key off, check PFE sensor supply tube for blockage or leaks. If these faults are found, repair as necessary. Connect all lines and repeat QUICK TEST. If no faults are found, service exhaust gas recirculation system.
18. EVR Filter Inspection. Turn key off. Remove and inspect EVR filter for contamination. A blocked filter will cause vacuum to be applied to EGR valve prematurely. If filter is contaminated, replace filter. Connect all lines and repeat QUICK TEST. If filter is not contaminated, replace EVR solenoid. Repeat QUICK TEST.
19. Codes 34 or 35: Check for Excessive Backpressure. Codes 34 and 35 in KOER SELF-TEST indicate excessive exhaust backpressure. There are 2 possible causes: the exhaust system is blocked, or faulty PFE sensor. Turn key off. Substitute known good PFE sensor in place of original. Repeat KOER SELF-TEST. If Code 34 or 35 is not displayed, replace PFE sensor. Repeat QUICK TEST. If Code 34 or 35 is displayed, check exhaust system for restrictions.
20. Code 33: Verify Vacuum at EGR Valve. Code 33 indicates PFE sensor input did not change after EVR solenoid received signal from ECA to open the EGR valve. Possible causes for this fault are as follows: Vacuum hose leaks. Obstructed vacuum hose. Faulty EVR solenoid. Faulty PFE sensor. Faulty EGR valve. Turn key off and wait 10 seconds. Using a vacuum "T", connect vacuum gauge at EGR valve. Perform KOER SELF-TEST while observing vacuum gauge. Disregard code output. If vacuum reading is greater than one in. Hg, go to step 26). If vacuum reading is one in. Hg or less, go to next step.
21. Vacuum Supply Hose Inspection. With key off, check vacuum hose from EVR solenoid to EGR valve and from vacuum source to EVR solenoid for loose connections, obstructions, cracks, etc. If vacuum hoses are damaged, repair or replace as necessary. Repeat QUICK TEST. If hoses are okay, go to step No. 24.
22. Supply Hose to EVR Verification. Turn key off and wait 10 seconds. Attach vacuum gauge to supply line between throttle body and EVR solenoid. Start and run engine at 2000 RPM. If vacuum reading is greater than 10 in. Hg, go to next step. If vacuum reading is less than 10 in. Hg, replace vacuum line to EVR, remove vacuum gauge and rerun QUICK TEST.
23. Checking PCV Valve for Operation. With key off, disconnect vacuum hose at PCV valve from EVR solenoid. Connect vacuum pump to PCV valve. Slowly apply 10 in. Hg vacuum. If PCV valve opens and does not leak down, remove vacuum gauge, reconnect valve and go to step 25). If PCV valve does not open, service or replace PCV valve.
24. Vacuum Supply to EVR Verification. Turn key off and wait 10 seconds. Attach vacuum gauge to source line from manifold. Start engine and run at idle. If vacuum is present, go to step 35). If no vacuum is present, replace vacuum hose to EVR solenoid and repeat QUICK TEST.
25. Checking EGR Valve Operation. With KOEO, disconnect vacuum hose at EGR valve. Connect vacuum pump to EGR valve. While observing EGR valve, slowly apply 10 in. Hg vacuum. The EGR valve should begin to open with a very small amount of vacuum (1-1.5 in. Hg) and be fully open with about 4 in. Hg. If EGR opens freely and smoothly, check EVR solenoid filter for obstructions. If filter is okay, replace EVR solenoid and rerun QUICK TEST. If EGR valve does not open freely and smoothly, service or replace EGR valve.
26. Checking PFE Sensor Supply Tube. With key off, check control pressure input tube to PFE sensor for cracks, obstructions or faulty connections. If supply tube is faulty, repair as necessary. If supply tube is okay, go to next step.
27. Substitute Known Good PFE Sensor. Turn key off and wait 10 seconds. Substitute known good PFE sensor in place of original. Rerun KOER SELF-TEST. If Code 33 is present, service or replace EGR valve as necessary. If Code 33 is not present, original PFE sensor was the cause of the original Code 33. Replace PFE sensor and rerun QUICK-TEST.
28. Continuous Memory Code 31 or 35: Testing PFE Sensor. Code 31 or 35 indicates that PFE sensor signal was less than (Code 31) or greater than (Code 35) the Self-Test voltage sometime during vehicle operation. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while performing the following steps. Connect a vacuum pump to PFE sensor and slowly apply 5 in. Hg vacuum to sensor. Slowly bleed vacuum off PFE sensor. Lightly tap on PFE sensor and wiggle PFE connector. If fault is indicated, disconnect harness and inspect connector. If connector and terminals are okay, replace PFE sensor. Repeat QUICK TEST. If no fault is indicated, go to next step.
29. Checking Harness. Observe VOM or diagnostic tester for fault indication while grasping harness close to sensor connector, then wiggling, shaking or bending small sections of harness while working your way to firewall. Also wiggle, shake or bend harness from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Repeat QUICK TEST. If fault is not indicated, go to next step.
30. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and terminals for damage. If connector and terminals are damaged, repair as necessary. Repeat QUICK TEST. If connector and terminals are okay, fault is intermittent and cannot be duplicated at this time.
31. Continuous Memory Code 34: Checking PFE Supply Tube for Blockage. Code 34 indicates that the PFE sensor was restricted sometime during vehicle operation. Turn key off. Remove PFE sensor and inspect sensor supply inlet for liquids or any type of blockage. Inspect PFE supply tube at EGR valve base for liquids or blockage. If supply tube is blocked, clean or service as necessary. Repeat QUICK TEST. If supply tube is not blocked, fault is intermittent and cannot be duplicated at this time.
32. Continuous Memory Code 32: Check EGR Valve Operation. Code 32 indicates that the EGR valve did not seat itself fully sometime during vehicle operation. Turn key off. Connect vacuum pump to EGR valve and apply 10 in. Hg of vacuum. While observing EGR valve, release vacuum, and repeat step if necessary. If EGR valve does not operate smoothly, service or replace EGR valve. If EGR valve works smoothly, go to next step.
33. Vacuum Line Inspection. Inspect EGR valve vacuum supply line, from EVR solenoid to EGR valve for kinks or obstructions. If vacuum supply line is blocked, repair as necessary. Repeat QUICK TEST. If vacuum supply line is okay, go to next step.
34. EVR Solenoid Filter Inspection. Carefully check EVR filter for contamination or obstructions. If EVR filter is contaminated, replace filter and repeat QUICK TEST. If EVR filter is not contaminated, fault is intermittent and cannot be duplicated at this time. Continuous Memory Code 32 testing is complete.
35. Continuous Memory Code 33: Checking EGR Valve Operation. Code 33 indicates that EGR valve intermittently did not open during vehicle operation. Turn key off. Connect a vacuum pump to EGR valve. While observing EGR valve, slowly apply 10 in. Hg of vacuum. EGR valve should begin to open at 1-1.5 in. Hg and be fully open at 4 in. Hg of vacuum. If EGR valve does not move freely and smoothly, service exhaust gas recirculation system. If EGR valve moves freely and smoothly, go to next step.
36. EVR Harness Test. With key off, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA to box. Enter OUTPUT STATE CHECK. Set DVOM on 20 volt scale. Connect DVOM negative test lead to test pin No. 40 at breakout box and DVOM positive test lead on test pin No. 33. Move throttle valve to indicate 10.5 volts or more and maintain position. While observing DVOM, grasp harness closest to EVR connector. Wiggle, shake or bend small sections of harness while working your way to firewall. Lightly tap EVR solenoid to simulate road vibration. If DVOM reads 10.5 volts or less, isolate fault and repair as necessary. Repeat QUICK TEST. If DVOM reads 10.5 volts or more, fault cannot be duplicated at this time. Continuous Memory Code 33 testing is complete.

B11 - EGR VALVE POSITION (EVP) SENSOR & EGR VALVE REGULATOR (EVR) SOLENOID

Note. Perform this test when Service Code 31, 32, 33, 34, 35, 38 or 84 is displayed during QUICK TESTS or when directed here by other test procedures.

EGR Valve Position (EVP) Sensor & EGR Valve Regulator (EVR) Solenoid Circuits. Scheme 72

1. Code 31: Generate Code 35. Code 31 indicates that EVP signal is less than the Self-Test minimum of 0.2 volt. Turn key off and wait 10 seconds. Disconnect EVP harness at sensor. Install a jumper wire between VREF and EVP SIGNAL at sensor harness connector. Perform KOEO SELF-TEST. Check for code 35. Ignore all other codes at this time. If Code 35 is displayed, remove jumper and replace EVP sensor. Repeat QUICK TEST. If Code 35 is not displayed, remove jumper wire and go to next step.
2. Checking VREF to SIG RTN Voltage. With KOEO and EVP disconnected, set DVOM on 20-volt scale. Measure voltage at EVP connector between VREF and SIG RTN. If reading is less than 4 or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, go to next step.
3. Checking EVP SIGNAL Continuity. With key off, wait 10 seconds. Disconnect EVP sensor, set DVOM on 200-ohm scale. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, and connect ECA to box. Measure resistance between EVP SIGNAL at connector and test pin No. 27. If reading is 5 ohms or more, repair open circuit. Connect EVP sensor and remove breakout box. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
4. Checking EVP SIGNAL For Shorts To Ground. With key off and EVP harness disconnected, leave breakout box installed and ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between EVP signal at EVP connector and ground. Measure resistance between test pin No. 27 and test pins No. 40, 46 and 60. If any reading is less than 10K ohms, repair short circuit. Connect EVP and remove breakout box. Repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA. Connect EVP and remove breakout box. Repeat QUICK TEST.
5. Code 35: Generate Code 31. Code 35 indicates EVP signal is greater than the Self-Test maximum of 4.81 volts. Turn key off and wait 10 seconds. Disconnect EVP sensor. Inspect for and repair any damaged wiring. Perform KOEO SELF-TEST. Check for Code 31. Ignore all other codes at this time. If code 31 is not displayed, go to step 7). If Code 31 is displayed, go to next step.
6. Checking VREF To SIG RTN Voltage. With EVP harness disconnected, set DVOM on 20-volt scale. With KOEO, measure voltage at EVP harness connector between VREF and SIG RTN. If reading is between 4 and 6 volts, replace EVP sensor. Repeat QUICK TEST. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1).
7. Checking EVP SIGNAL For Short To Power. Turn key off and disconnect EVP from harness. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 27 and test pins No. 26 and 57. If either reading is less than 10K ohms, repair short in harness. Connect EVP sensor and remove breakout box. Repeat QUICK TEST. If both readings are 10K ohms or more, replace ECA. Connect EVP sensor and remove breakout box. Repeat QUICK TEST.
8. Code 84: EVR Solenoid Resistance. Code 84 indicates a faulty EVR circuit. Turn key off. Set DVOM on 200-ohm scale. Disconnect EVR solenoid connector and measure solenoid resistance. If reading is less than 30 ohms or more than 70 ohms, replace EVR solenoid assembly. Repeat QUICK TEST. If reading is between 30 and 70 ohms, go to next step.
9. Checking VPWR at EVR Solenoid. Leave EVR solenoid disconnected and set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between negative battery terminal and VPWR circuit at EVR solenoid harness connector. If reading is less than 10.5 volts, repair VPWR open circuit. Repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
10. EVR Circuit Continuity. With key off and EVR solenoid disconnected, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 33 and EVR SIGNAL at EVR solenoid connector. If reading is 5 ohms or more, repair open circuit. Connect EVR solenoid and remove breakout box. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
11. Checking EVR Circuit Shorts. With key off, breakout box installed, and ECA and EVR solenoid disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pin No. 33 and test pins No. 37 and 57, 40, 60, and 46 at breakout box. If any reading is less than 10K ohms, repair short circuit. Remove breakout box, and connect ECA and EVR solenoid. Repeat QUICK TEST. If code is repeated, replace ECA. If all readings are 10K ohms or more, replace ECA. Remove breakout box, and connect ECA and EVR solenoid. Repeat QUICK TEST.
12. KOEO Code 34: Check For Code 84. KOEO Code 34 indicates EGR valve and/or EVP is not fully seated in the closed position. EVP voltage signal, in the closed position, is greater than the Self-Test maximum of 0.67 volt. Because of the preload on the installed EVP sensor it is very difficult to determine if the EGR valve is seated or the EVP sensor is in contact with the EGR valve. Turn key off and wait 10 seconds. Check for Code 84 in KOEO SELF-TEST. If Code 84 is present, go to step 8). If Code 84 is not displayed, go to next step.
13. Functional Test of EVP Sensor and EGR Valve. Turn key off and wait 10 seconds. Disconnect EVP sensor. Inspect harness and connector, service as necessary. Remove vacuum line from EGR valve. Test EGR valve operation by applying and releasing vacuum to valve, using a vacuum pump. Reconnect vacuum line. Repeat KOEO and KOER SELF-TEST. If Code 34 is still displayed, go to next step. If Code 34 is not displayed, the original code was set by a faulty connection or a sticking EGR valve. Testing of EGR valve is complete.
14. Substitute EVP Sensor on Original EGR Valve. Turn key off and wait 10 seconds. Install a good known EVP sensor on original EGR valve. Perform KOEO SELF-TEST. If Code 34 is present, check EGR valve for mechanical malfunction. If Code 34 is not present, replace original EVP sensor. Repeat QUICK TEST.
15. KOEO and KOER Code 32 Checking EVP and EGR. Code 32 indicates that EGR valve and/or EVP sensor signal voltage is less than closed position minimum of 0.29 volt. Preload on EVP sensor makes it difficult to determine whether the EGR valve has malfunctioned or if the EVP sensor has abnormally high resistance. Possible causes for this fault are: poor continuity at EVP sensor connector, non-seated or faulty EGR valve or faulty EVP sensor. Turn key off and wait 10 seconds. Inspect connector and harness for damage and service as necessary. Remove vacuum line from EGR valve. Test EGR valve operation by applying and releasing vacuum to valve, using a vacuum pump. Reconnect vacuum line. If Code 32 is still present, go to next step. If Code 34 is not displayed, the original code was set by a faulty connection or a sticking EGR valve. Testing of EGR valve is complete.
16. Substitute EVP Sensor On Original EGR Valve. Turn key off and wait 10 seconds. Install a known good EVP sensor on original EGR valve. Perform KOEO SELF-TEST. If Code 32 is present, check EGR valve for mechanical malfunction. If Code 32 is not present, replace original EVP sensor. Repeat QUICK TEST.
17. KOER Code 33: Checking Vacuum at EGR. KOER Code 33 indicates that EVP sensor input did not change after ECA signaled EGR operation. Because a Code 84 was not received in the KOEO SELF-TEST, the EVR solenoid electrical function is okay. The lack of Code 32 or 34 indicate the EVP sensor is within the closed position specifications. Possible causes for this fault are; leaking vacuum hose, restricted vacuum hose, restricted EVR solenoid filter, or a faulty EGR valve. Turn key off. Using vacuum "T", connect vacuum gauge at EGR valve. Perform KOER SELF-TEST and observe vacuum gauge. If reading is 1.5 in. Hg or greater, go to step 20). If reading is less than 1.5 in. Hg, remove vacuum gauge and reconnect EGR valve, or go to next step.
18. Checking Vacuum Supply to EVR Solenoid. Turn key off. Disconnect vacuum source to EVR solenoid. Install vacuum gauge at source vacuum hose. Start engine. If reading is 10 in. Hg or more, go to next step. If reading is less than 10 in. Hg, check vacuum hose to EVR solenoid. Replace if necessary. Repeat QUICK TEST.
19. Checking Vacuum Hoses. Carefully check vacuum line for cracks, loose connections, blockage, kinks, and leaks. If vacuum hose is not okay, replace hose. Connect new vacuum hose and repeat QUICK TEST. If vacuum hose is okay, check EVR solenoid filter for obstructions. Replace if necessary. If filter is okay, replace EVR solenoid. Connect all vacuum hoses and repeat QUICK TEST.
20. Checking EVP Sensor and EGR Valve. Turn key off and wait 10 seconds. Disconnect EVP sensor. Inspect connector and harness or damage and service as necessary. Remove vacuum line from EGR valve. Test EGR valve operation by manually depressing and releasing the diaphragm. Reconnect vacuum line to EGR valve and connector to EVP sensor. Repeat KOEO and KOER SELF-TEST. If Code 33 is still present, go to next step. If Code 33 is not displayed, the original code was set by poor continuity or a sticking EGR valve. Testing of EGR valve is complete.
21. Checking EGR Valve Vacuum Control. With key off, disconnect EGR valve vacuum supply. Connect a vacuum gauge to EGR valve and apply 2-3 in. Hg for 2 minutes. If EGR holds vacuum, reconnect supply line and go to next step. If EGR valve will not hold vacuum, service or replace EGR valve.
22. Substitute Known Good EVP Sensor. Turn key off and wait 10 seconds. Install a known good EVP sensor on original EGR valve. Perform KOER SELF-TEST. If Code 33 is present, check EGR valve and/or system for mechanical malfunction. If Code 33 is not present, service or replace original EVP sensor. Repeat QUICK TEST.
23. Code 34: EGR Valve Operation. Code 34 indicates that EVP voltage is greater than closed position Self-Test minimum of 0.67 volts. Turn key off. Disconnect and plug EGR valve vacuum hose. Perform KOER SELF-TEST. If Code 34 is not present, check EVR filter for obstructions. Replace if necessary. If filter is okay, replace EVR solenoid. Connect all vacuum hoses and repeat QUICK TEST. If Code 34 is present, go to next step.
24. Checking EVP Resistance, While Applying Vacuum to EGR. Turn key off and wait 10 seconds. Disconnect harness from EVP sensor. Inspect connectors for damaged pins or corrosion. Repair if necessary. Set DVOM on 200K-ohm scale. Disconnect vacuum hose to EGR valve and connect vacuum pump to valve. Measure resistance at EVP sensor between EVP SIGNAL and VREF while gradually increasing vacuum to 10 in. Hg. If reading decreases from no more than 5500 ohms to no less than 100 ohms, check EGR valve for mechanical malfunction and service or replace as necessary. If reading does not change as indicated, replace EVP sensor. Reconnect vacuum hose and rerun QUICK TEST.
25. Continuous Memory Code 32: Check EVP Signal Voltage While Operating EGR. Code 32 indicates that EGR valve closed further than normal with engine at idle and at normal operating temperature. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Connect vacuum pump to EGR valve. Place DVOM on 20-volt scale and connect between test pins No. 27 and 46. With KOEO, observe DVOM readings. Slowly apply 6 in. Hg vacuum to EGR valve. Slowly bleed vacuum off EGR valve and lightly tap on EVP sensor to simulate road shock. If voltage drops to less than .29 volt, the EGR valve may have caused Code 32. Clear Continuous Memory Codes. Check EGR valve for mechanical malfunction. If all readings are more than .29 volt, Code 32 fault cannot be duplicated at this time. Testing is complete.
26. Continuous Memory Code 31 and/or 35: Check Harness. Code 31 indicates an open in the EVP SIGNAL or VREF, or a short to SIG RTN with the engine at idle and at normal operating temperature. Code 35 indicates a short to VREF and/or VPWR, or an open in SIGNAL RETURN with the engine at idle and at normal operating temperature. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for fault indication while grasping harness close to sensor and wiggling, shaking, or bending a small section of EEC-IV harness while working toward dash panel. Wiggle, shake or bend harness from firewall to ECA. If fault is indicated, isolate fault and repair wiring harness as required. Repeat QUICK TEST. If fault is not found, go to next step.
27. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector and terminals for obvious damage. If connector and terminals are damaged, repair as necessary. Repeat QUICK TEST. If connector and terminals are okay, fault cannot be duplicated at this time. Test is completed.
28. Continuous Memory Code 33: Leak Test. Code 33 indicates that EGR valve did not open with the engine at normal operating temperature and with the EVR solenoid signal present. Turn key off and wait 10 seconds. Connect vacuum pump to EGR valve. Apply 20 in. Hg to EGR valve. If EGR valve opens and holds vacuum, go to next step. If not, service or replace EGR valve as necessary, clear codes and repeat QUICK TEST.
29. EVR Check. Using CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for fault indication. Grasp harness close to EVR solenoid connector and wiggle, shake, or bend a small section of harness while working toward ECA. Inspect connectors and terminals for obvious damage. If fault is indicated, isolate fault and repair as necessary. Repeat QUICK TEST. If no fault is indicated, fault cannot be duplicated at this time. Testing is complete.
30. Continuous Memory Code 34: EVP Resistance Check While Operating EGR Valve. Code 34 indicates EGR valve was open with the engine idling at normal operating temperature. Turn key off. Disconnect harness from EVP sensor. Inspect connector for obvious damage. Place DVOM on 200K-ohm scale. Disconnect vacuum hose to EGR valve and connect vacuum pump to valve. Measure resistance at EVP sensor between EVP SIGNAL and VREF at the sensor while increasing vacuum to 10 in. Hg. If reading does not decrease gradually from up to 5500 ohms to not less than 100 ohms, check EGR valve for mechanical malfunction. If reading gradually decreases from no more than 5500 ohms to no less than 100 ohms, go to next step.
31. EVR Check. Turn key off. Disconnect vacuum hose from EGR valve and plug hose. Perform KOER SELF-TEST. If Code 34 is present, check EVR filter for obstructions. Replace if necessary. If filter is okay, replace EVR solenoid. Connect all vacuum hoses and repeat QUICK TEST. If Code 34 is not present, fault cannot be duplicated at this time. Testing is completed.

B12 - VEHICLE SPEED SENSOR (VSS)

Note. Perform this test when Service Code 29 is displayed during QUICK TESTS or when directed here by other test procedures.

Vehicle Speed Sensor Circuit. Scheme 73

To prevent replacement of good components, be aware that the following circuit test is to be used only when Continuous Memory Code 29 is displayed. This test checks vehicle speed sensor, wiring harness, and ECA. Before testing the VSS perform the following drive cycle procedure.

Automatic Transmission Equipped Vehicles. Record and clear CONTINUOUS SELF-TEST codes. Warm engine to normal operating temperature. In Low gear, accelerate moderately to 25 MPH and coast down to idle and stop. Shut off engine. Perform KOEO SELF-TEST. If Code 29 is present, go to step 1). If not, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST. If codes are not present, test is completed.

Manual Transmission Equipped Vehicles. Record and clear CONTINUOUS SELF-TEST codes. Warm engine to normal operating temperature. Start in first gear, shift to second gear, and accelerate moderately to 40 MPH. Coast down to idle and stop. Shut engine off. Perform KOEO SELF-TEST. If Code 29 is present, go to next step. If not, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST. If codes are not present, test is completed.

1. Continuous Memory Code 29. Code 29 indicates there is insufficient input to the ECA from the VSS. Possible causes for this code are a faulty VSS, open or shorted circuit or a faulty ECA. Perform drive cycle procedure. If Code 29 is displayed or driveability complaint can be verified, go to next step. If not, fault cannot be duplicated at this time.
2. Checking VSS Sensor. Turn key off and wait 10 seconds. Disconnect vehicle speed sensor. Set DVOM on 200K-ohm scale. Measure resistance across vehicle speed sensor. If reading is between 190-240 ohms, go to next step. If reading is incorrect, replace vehicle speed sensor and repeat drive cycle procedure.
3. VSS Harness Continuity. Turn key off and wait 10 seconds. Remove ECA 60-pin connector and inspect for damaged pins, corrosion, or loose wires. Repair as necessary. Install breakout box. With ECA and VSS disconnected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 3 at breakout box and VSS harness connector. Also measure resistance between test pin No. 6 at breakout box and VSS harness connector. If both readings are 5 ohms or less, go to next step. If readings are 5 ohms or more, service open circuit in VSS wiring harness. After repairs, repeat step 1).
4. Checking VSS Harness For Shorts. Turn key off. With ECA and VSS disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pin No. 3 and test pins No. 37, 40 and 6 at breakout box. Also measure resistance between test pin No. 6 and test pin No. 37. If all readings are greater than 10K ohms, go to next step. If any reading is less than 10K ohms, repair short(s) in VSS wiring harness. After repairs, repeat step 1).
5. Test By Substitution. Substitute VSS with known good sensor and repeat drive cycle procedure. Connect ECA and VSS. Repeat step 1), and return to this step. If Code 29 is present, replace ECA and repeat step 1). If no code is present, replace original vehicle speed sensor.

B13 - NEUTRAL DRIVE SWITCH (NDS) A/C INPUT

Note. Perform this test when Service Code 67 or 79 is displayed during QUICK TESTS or when directed here by other test procedures. This test is designed to diagnose the following

1. A/C input to ECA.
2. Clutch engagement switch.
3. Neutral clutch switch.
4. Neutral drive switch.
5. ECA
6. Harness connector and electrical circuits.

Scheme 74

Scheme 75

Scheme 76

Scheme 77

Scheme 78

Scheme 79

1. Code 67 System Identification. Code 67 indicates that during engine cranking or KOEO SELF-TEST, signal voltage was greater than specification at test pin No. 10 (A/C input) or test pin No. 30 (NDS). Possible causes for this fault are: A/C circuit shorted to power, Neutral clutch/drive circuits open, Neutral clutch/drive switch open, or a faulty ECA. To continue test, go to appropriate test step. 2.3L OHC MPFI M/T Go to step 2. 2.3L T/C M/T Go to step 6. (Scheme 74): Neutral Gear/Clutch Circuit Diagram
2. Checking Neutral Gear/Clutch Input. Turn key off and wait 10 seconds. Ensure A/C control is in "OFF" position. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leave ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 30 and 46 should be infinite with transmission in Neutral and clutch pedal in the up position. Measure resistance with transmission in gear and clutch pedal depressed. If both resistances are less than 5 ohms. On vehicles with A/C go to step 9). If vehicle is not equipped with A/C, replace ECA. If reading is more than 5 ohms, go to next step.
3. Checking Neutral Gear/Clutch Switch. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Locate Neutral Gear Switch (NGS) on transmission and clutch switch at clutch pedal linkage. Disconnect harness at both switches and inspect connector pins. Set DVOM on 200-ohm scale and measure resistance across NGS with transmission in Neutral, and across clutch switch terminals with clutch pedal depressed. If both resistances are less than 5 ohms, go to next step. If all resistances are more than 5 ohms, replace open switches, remove test equipment, reconnect components and repeat QUICK TEST.
4. Checking Neutral Gear/Clutch Switch Harness. Turn key off and wait 10 seconds. Install breakout box, leave ECA disconnected and set DVOM to 200-ohm scale. Disconnect harness at NGS and clutch switch. Measure resistance between test pin No. 30 and NGS harness connector and, between test pin No. 30 and clutch switch harness connector. Measure resistance between test pin No. 46 and NGS harness connector, and between test pin No. 46 and clutch switch harness connector. If all resistances are less than 5 ohms, on vehicles equipped with A/C, go to step 9). If not equipped with A/C, replace ECA. If any reading is greater than 5 ohms, repair open in harness or connector. Repeat QUICK TEST. (Scheme 75): Clutch Engage Switch Circuit Diagram NOTE: If clutch pedal is not depressed during KOEO test, a Code 67 will be displayed.
5. Checking Clutch Engage Switch. Turn key off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and leave ECA disconnected. Set DVOM on 200-ohm scale. Depress clutch pedal. Measure resistance between test pin No. 30 and test pin No. 46. If both readings are less than 5 ohms, on vehicles equipped with A/C, go to step 9). If not equipped with A/C, replace ECA. If any reading is 5 ohms or more, repair open circuit. (Scheme 76): Neutral Input Circuit Diagram (2.3L Turbo M/T)
6. Checking Neutral Input Circuit: 2.3L Turbo MPFI With M/T. Turn key off, wait 10 seconds. Ensure A/C is turned off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box. Leave ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 30 and 46. If resistance is less than 5 ohms, on vehicles equipped with A/C, go to step 9). If vehicle is not equipped with A/C, replace ECA. If reading is more than 5 ohms, repair open circuit. Rerun QUICK TEST. (Scheme 77): Neutral Drive Input Circuit Diagram
7. Checking Neutral Drive Input. Turn key off and wait 10 seconds. Ensure heater control is in "OFF" position. Ensure transmission is in Neutral or Park position. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and leave ECA disconnected. Set DVOM to 20-volt scale. Connect ECA to breakout box. With KOEO, measure voltage between test pin No. 30 at the breakout box and chassis ground. If voltage is less than one volt, on vehicles equipped with A/C, go to step 9). If not equipped with A/C, replace ECA. If reading is more than one volt, go to next step.
8. Checking Neutral Drive Switch. Turn key off and wait 10 seconds. Install breakout box, leave ECA disconnected. Set DVOM on 200-ohm scale. Disconnect vehicle harness from NDS at transmission and measure resistance across switch. If resistance is less than 5 ohms, remove breakout box. Reconnect all components and service open in NDS circuit. If resistance is more than 5 ohms, replace NDS and rerun QUICK TEST. (Scheme 78): A/C Input Circuit Diagram
9. Checking A/C Input Voltage. Ensure A/C is switched "OFF". If A/C was on, rerun QUICK TEST. If Code 67 or 79 is displayed, continue with this test. Install breakout box and leave ECA disconnected. With KOEO, set DVOM on 20-volt scale. Measure voltage at test pin No. 10 at the breakout box and chassis ground. If reading is greater than one volt, remove breakout box and repair short in A/C clutch power circuit. If voltage is less than one volt replace ECA, except on vehicles equipped with E4OD transmissions. Reconnect all components and rerun QUICK TEST.
10. Checking A/C Input Circuit. A low idle with A/C switched "ON" could result in the ECA not receiving or recognizing A/C input on pin No. 10. Turn key off and wait 10 seconds. Disconnect ECA, inspect pins, and install breakout box. Leave ECA disconnected. Set DVOM on 20-volt scale. With KOEO, and A/C on, measure voltage between test pins No. 10 and 40. If voltage is greater than 10.5 volts, replace ECA. Reconnect all components and rerun QUICK TEST. If voltage is less than 10.5 volts, service open in A/C circuit and rerun QUICK TEST. (Scheme 79): A/C Clutch Circuit Diagram
11. Checking Inoperative A/C With High Idle. A high idle condition with the A/C dash switch in the "ON" position may be the result of a lack of signal reaching the A/C clutch. Turn key off and wait 10 seconds. Disconnect ECA, inspect pins, and install breakout box. Leave ECA disconnected. Disconnect A/C clutch connector. Set DVOM on 20-volt scale. With KOEO, turn on A/C. Measure voltage between input pin on fan connector and test pin No. 40 at the breakout box. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open circuit and rerun QUICK TEST.
12. Check Continuity of A/C Clutch. With KOEO, disconnect A/C clutch harness connector. Measure resistance across both pins of A/C clutch. If resistance is within normal specification of 2.14-3.34 ohms, fault was probably due to faulty connection. If resistance was not within specification repair or replace A/C clutch as necessary.
13. Checking Continuity of A/C Cycle Pressure Switch Circuit. Turn key off and wait 10 seconds. Disconnect ECA, inspect pins, and install breakout box. Leave ECA disconnected. Disconnect A/C cycle pressure switch. Turn on A/C switch. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 43 at the breakout box and battery positive side of the A/C cycle pressure switch. Measure resistance between test pin No. 10 at the breakout box and negative side of the A/C cycle pressure switch connector. If both resistances are less than 5 ohms, EEC-IV system is not at fault. Repair or replace cycle pressure switch. If resistances are greater than 5 ohms, repair open circuit and rerun QUICK TEST.
14. Check A/C Demand and A/C Cycle Pressure Switch For Short to Power. Turn key off. Disconnect ECA, inspect pins, and install breakout box. Leave ECA disconnected. Ensure A/C switch is off. Set DVOM on 20-volt scale. With KOEO, measure voltage between test pin No. 43 and chassis ground. If voltage is greater than 1.0 volt, EEC-IV is not at fault. Repair or replace A/C switches or electrical circuit. If voltage is less than 1.0 volt, reconnect components and check switch operation. If switches are okay, repair short in circuit wiring and rerun QUICK TEST.
15. Checking NDS Circuit For Short to Ground or Closed NDS. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector, inspect pins, and install breakout box. Place transmission in Drive. Set DVOM on 200K-scale. Measure resistance between test pin No. 30 and test pin No. 40 or 60 at breakout box. If resistance is greater than 10K ohms service high idle condition. If resistance is less than 10K ohms, service circuit short or closed NDS and retest.

B14 - BRAKE ON/OFF SWITCH (BOO)

Note. Perform this test when Service Code 74 or 75 is displayed during QUICK TESTS or when directed here by other test procedures.

Brake ON/OFF (BOO) Circuit (2.3L OHC EFI). Scheme 80

Brake ON/OFF (BOO) Circuit (2.3L EFI). Scheme 81

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: brake light bulb, brake light switch, or brake light fuse. This test is intended to diagnose a faulty BOO circuit or ECA.

1. Code 74: Verify Brake Pedal Was Depressed. If brake was NOT depressed during KOER SELF-TEST, repeat test and depress brake pedal ONLY once during test. Depress and release brake pedal AFTER dynamic response code but before brief WOT. If pedal was depressed, go to next step.
2. Checking Power Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, and loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pins No. 2 and 40 while applying and releasing brake. If voltage cycles, switch circuit is okay, replace ECA and repeat QUICK TEST. If voltage does not cycle, go to next step.
3. Checking For Shorts To Ground. Turn key off. Leave breakout box installed and ECA disconnected. Set DVOM on 200K-ohm scale. Disconnect BOO circuit at 12-pin connector (14290 Harness). Measure resistance between test pins No. 2 and 40 at the breakout box. If resistance is greater than 10K ohms, repair stoplamp circuit as necessary. If resistance is less than 10K ohms remove breakout box repair short, and repeat KOER SELF-TEST.
4. Code 75 Displayed. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Disconnect BOO from Transmission Hydraulic Switch 12-pin connector (14290 Harness). Measure resistance between test pin No. 2 and BOO circuit at the 12-pin connector (14290 Harness). If resistance is greater than 5 ohms, remove breakout box. Reconnect ECA, repair open circuit, and rerun SELF-TEST.
5. Code 75: Cycle BOO Circuit. Turn key off. With breakout box installed and ECA disconnected, set DVOM on 20-volt scale. Measure voltage between test pins No. 2 and 40 at the breakout box while depressing and releasing the brake pedal. If voltage cycles, remove breakout box. Replace ECA, and rerun QUICK TEST. If voltage does not cycle, go to next step.
6. Checking BOO Circuit For Short To Power. Turn key off. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Disconnect BOO circuit at 12-pin connector. Measure voltage between test pin No. 2 at the breakout box and engine block ground. If voltage is greater than 10.5 volts, BOO circuit is okay. Check and repair brake light circuit as necessary. If voltage is less than 10.5 volts, remove breakout box. Reconnect ECA, repair circuit short and rerun QUICK TEST.
7. Code 74: Verify Brake Pedal Was Depressed. Code 74 indicates that brake was NOT depressed during KOER SELF-TEST, the BOO signal did not cycle during test. Repeat test and depress brake pedal ONLY once during test. Depress and release brake pedal AFTER dynamic response code, but before brief WOT. If pedal was depressed, go to next step. If voltage did not cycle, repeat KOER SELF-TEST and depress brake pedal once during test.
8. Checking BOO Circuit Cycling. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, and loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pins No. 2 and 40 while applying and releasing brake. If voltage cycles, switch circuit is okay, replace ECA and repeat QUICK TEST. If voltage does not cycle, go to next step.
9. Checking Continuity of BOO Circuit. Turn key off. Leave breakout box installed and ECA disconnected. Set DVOM on 200-ohm scale. Disconnect BOO circuit at 12-pin connector (12A581 to 14290 or 14401 Harness Connector). Measure resistance between test pins No. 2 and 40 at the breakout box. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms remove breakout box repair open circuit, and repeat KOER SELF-TEST.
10. Checking BOO Circuit For Short to Power. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Disconnect BOO from Transmission Hydraulic Switch 12-pin connector (12A581 to 14290 or 14401 Harness). Measure voltage between test pin No. 2 at the breakout box and engine block ground. If voltage is greater than 1.0 volt, remove breakout box. Reconnect ECA, repair short circuit, and rerun SELF-TEST. If voltage is less than 1.0 volt, go to next step.
11. Check BOO Circuit For Short to Ground. Turn key off. Leave breakout box installed and ECA disconnected. Set DVOM on 200K ohm scale. Disconnect BOO circuit at 12-pin connector (12A581 to 14290 or 14401 Harness Connector). Measure resistance between test pin No. 2 and test pin No. 40 at the breakout box. If resistance is greater than 10K ohms, repair stoplamp circuit as necessary. If resistance is less than 10K ohms remove breakout box repair short, and repeat KOER SELF-TEST.

B15 - POWER STEERING PRESSURE SWITCH (PSPS)

Note. Perform this test when Service Code 52 is displayed during QUICK TESTS or when directed here by other test procedures. Some vehicles ECA's may be equipped with PSPS software strategy but DO NOT have power steering. If a KOEO Code 52 is displayed, check to see that vehicle is equipped with power steering. If not, disregard Code 52.

Power Steering Pressure Switch (PSPS) Circuit. Scheme 82

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: idle speed/throttle stop adjustment, binding throttle shaft/linkage or cruise control linkage.

1. Code 52 Elimination. Code 52 indicates that PSPS circuit is open. Turn key off and wait 10 seconds. Disconnect PSPS. Install a jumper wire between PSPS circuit and SIG RTN at harness connector. Repeat KOEO SELF-TEST. If Code 52 is not displayed, replace PSPS and repeat QUICK TEST. If Code 52 is still displayed, go to next step.
2. PSPS Harness Check. Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale and measure resistance between test pin No. 46 and SIG RTN at the PSPS harness connector. Also measure resistance between PSPS CKT. at the harness connector and test pin No. 24. If both readings are less than 5 ohms, replace ECA. Repeat QUICK TEST. If readings are greater than 5 ohms, repair open in circuit. Repeat QUICK TEST.
3. Checking Switch Integrity. Connect tachometer and start engine. Allow engine to idle in Park or Neutral. Disconnect PSPS at switch. If RPM increases, replace PSPS. If RPM does not increase, go to next step.
4. Checking PSPS Harness. Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 24 and test pin No. 46 at the breakout box. If resistance is 10K ohms or less, repair short in harness. If reading is greater than 10K ohms, replace ECA. Repeat QUICK TEST.
5. KOER SELF-TEST Code 52 Displayed. If you turned steering wheel 1/2 turn within 1-2 seconds AFTER engine ID code, but BEFORE dynamic response code, go to next step. If steering wheel was not turned, ensure front wheels are centered (no load condition). Repeat QUICK TEST.
6. Checking ECA Open Circuit Identifying Capabilities. Turn key off and wait 10 seconds. Disconnect PSPS. Perform KOEO SELF-TEST. If Code 52 is present, go to step 8). If Code 52 is not present, go to next step.
7. PSPS Harness Check. Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box, leaving ECA disconnected, and set DVOM on 200K-ohm scale. Measure resistance between test pins No. 46 and 24 at breakout box. If reading is 10K ohms or less, repair short to SIG RTN in PSPS circuit. Repeat QUICK TEST. If reading is 10K ohms or more, replace ECA and repeat QUICK TEST.
8. PSPS Position Comparison. Turn key off and wait 10 seconds. Install breakout box, leaving ECA connected. With PSPS connected, set DVOM on 200-ohm scale. Turn key on and measure resistance between test pins No. 24 and No. 46. Start engine. If reading remains less than 10 ohms between KOEO and KOER, go to next step. If not, go to step 11).
9. PSPS Position: Load/No Load. Install breakout box and connect ECA. Connect PSPS and set DVOM on 200-ohm scale. Start engine and allow it to idle. Measure resistance between test pins No. 24 and No. 46 at breakout box. Turn steering wheel 1/2 turn and return. If reading changes from less than 10 ohms to infinity (indicating PSPS opening) and then returns to 10 ohms or less (when steering wheel is centered), PSPS system is okay. Remove breakout box and return to QUICK TEST. If reading did not change as indicated, go to next step.
10. PSPS Closed or Low Hydraulic Pressure. At this point, there are only 2 possible causes for the original Code 52. They are a PSPS switch that will not open, or low available hydraulic pressure. Turn key off and wait 10 seconds. Substitute original switch with a known good PSPS switch. Perform KOER SELF-TEST and turn steering wheel at least 1/2 turn after engine ID code. If Code 52 is still present, check for low hydraulic pressure. If Code 52 is not present, replace original PSPS switch. Service other codes if necessary.
11. PSPS Always Open or High Hydraulic Pressure. At this point, there are only 2 possible causes for original Code 52. They are a PSPS switch that is always open, or excessively high hydraulic pressure. Turn key off and wait 10 seconds. Substitute original switch with a known good PSPS switch. Perform KOER SELF-TEST and turn steering wheel at least 1/2 turn after engine ID code. If Code 52 is still present, check for high hydraulic pressure. If Code 52 is not present, replace original PSPS switch. Service other codes if necessary.

C1 - FUEL CONTROL - ALL APPLICATIONS

Note. Perform this test when Service Code 41, 91, 42, 92, 43, 65, 85, 86 or 93 is displayed during QUICK TESTS or when directed here by other test procedures.

See HOW TO USE CIRCUIT TESTS, at beginning of circuit tests before performing this test. Fuel contaminated engine oil may affect Service Codes 41, 91 and 42, 92. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter.

To prevent replacement of good components, be aware of the following non-EEC areas which may be cause of driveability concerns

1. Ignition coil, distributor cap or rotor
2. Faulty spark plugs or wires
3. Faulty CANP system
4. DIS ignition system
5. EGR valve and gasket
6. Air filter
7. Fuel or engine oil contamination
8. Poor electrical ground
9. Faulty fuel pressure
10. Intake or exhaust manifold leaks
11. Engine below normal operating temperature

This test is intended to diagnose only the following components

Scheme 83

Scheme 84

1. HEGO sensor
2. HEGO signal and ground circuit
3. HEGO sensor connection
4. Vacuum systems
5. Fuel injector
6. ECA
7. Electrical circuits HEGO GRD, HEGO, INJ 1-8, and VPWR PASSENGER CAR - INDIVIDUAL INJECTOR RESISTANCE Engine Ohms 2.3L OHC MPFI 15.0-19.0 2.3L Turbo MPFI 2.0-3.0 2.3L HSC MPFI 13.5-16.0 CAR - INJECTOR BANK RESISTANCE Engine Ohms 2.3L OHC MPFI 7.0-9.5 2.3L Turbo MPFI 1.2-1.8 2.3L HSC MPFI 7.0-9.5 TRUCK - INDIVIDUAL INJECTOR RESISTANCE Engine Ohms 2.3L MPFI 13.5-18.0 TRUCK INJECTOR BANK RESISTANCE Engine Ohms 2.3L MPFI 7.0-9.5 CAR - FUEL PRESSURE SPECIFICATIONS: psi (kg/cm 2 ) Pressure KOER Pressure KOEO 30-45 (2.11-3.16) 35-45 (2.46-3.16) 30-55 (2.11-3.87) 35-45 (2.46-3.16) 45-60 (3.16-4.22) 50-60 (3.52-4.22) TRUCK - FUEL PRESSURE SPECIFICATIONS: psi (kg/cm 2 ) Pressure KOER Pressure KOEO 30-45 (2.11-3.16) 35-45 (2.46-3.16) (Scheme 83): All MPFI (Except 2.3L MPFI Turbo) Test Schematic (Scheme 84): 2.3L MPFI Turbo Test Schematic

Scheme 85

1. Checking Fuel Pressure. Turn ignition key off, wait 10 seconds. Install fuel pressure gauge. Verify that manifold vacuumsupply is connected to fuel pressure regulator (if equipped). Run engine at idle and check fuel pressure. If vehicle will not start, cycle key on and off several times. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is within specification, go to next step. If pressure is not to specification, remove fuel pressure gauge. Repair electric fuel pump or fuel pressure regulator.
2. Checking Fuel Pressure Check Valve. With KOEO, check that fuel pressure remains to specification for approximately 60 seconds. If system holds pressure, go to next step. If system does not hold pressure, go to step 6) for all engine applications except SEFI. For SEFI engines, go to step 9).
3. Fuel Delivery Test. Ensure fuel is of good quality. With key off, install fuel pressure gauge and pressurize fuel system as in step 1). Disconnect inertia switch. Crank engine for 5 seconds. If fuel pressure drop is greater than 5 psi after 5 seconds of cranking, the EEC-IV system is not the cause of the no start condition. Check additional DIAGNOSIS BY SYMPTOM tests. Reconnect inertia switch and remove fuel pressure gauge. If problem is rough running, missing, or a fuel service code, go to next step. For SEFI engine vehicles, go to step 9). If fuel pressure drop is less than 5 psi, remove fuel pressure gauge, reconnect inertia switch, and go to next step.
4. Checking Injector and Harness Resistance. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect pins for damage. Install breakout box, leave ECA disconnected, and set DVOM on 200-ohm scale. MPFI Engines - Measure resistance of injector banks between test pins No. 37 and 58 (bank No. 1) or 59 (bank No. 2) at breakout box. Record resistance. Refer to INJECTOR BANK RESISTANCE table. SEFI Engines - Measure resistance between suspect cylinder test pin (from Cylinder Balance Test) and test pin No. 37, at the breakout box. Refer to INJECTOR BANK RESISTANCE table. For No Starts: Choose any injector and measure resistance between that injector circuit test pin and test pin No. 37, at breakout box. Record resistance. CFI Engines - Measure resistance of injector circuit between test pins No. 37 and 58, at the breakout box. Record resistance. Compare resistance obtained above with appropriate specification in INJECTOR BANK RESISTANCE table. If injector is within specification, go to step 6). If injector is not within specification, do the following: MPFI Engines - Go to next step. SEFI Engines - Remove breakout box and reconnect ECA. Service open/short in harness/connector. If okay, replace injector. Rerun QUICK TEST and Cylinder Balance Test. For No Start: Service open in VPWR circuit. CFI Engines - Remove breakout box and reconnect ECA. Repair open/short in harness/connector. If okay, replace injector. Rerun QUICK TEST.
5. Isolating Faulty Injector Circuit. Turn key off. Install breakout box and disconnect ECA. Disconnect all injectors on suspect bank. With DVOM set on 200-ohm scale, connect one injector and measure resistance between test pins No. 37 and 58 or 59. Disconnect injector and repeat process for all other injectors. See INDIVIDUAL INJECTOR RESISTANCE table for specifications. If injectors are within specifications, go to step 6). If injectors are not to specification, remove breakout box, reconnect ECA and injectors. Repair open/short in injector harness. If okay, replace injector. Rerun QUICK TEST.
6. Checking Injector Drive Signal. With key off and breakout box installed, connect ECA to breakout box. Use a non-powered 12-volt test light and the following connection procedure: MPFI Engines - Connect test light between test pins No. 37 and 58 at the breakout box. Connect light between test pins No. 37 and 59 at the breakout box. SEFI Engines - Connect test light between test pin No. 37 and the suspect injector(s) test pin at the breakout box. CFI Engines - Connect test light between test pins No. 37 and 58, at the breakout box. Crank or start engine. A properly operating system is indicated by a test light that glows dimly. If light glows dim, go to next step; except on SEFI engines. On SEFI engine, remove breakout box and reconnect ECA. Clean and test injectors. Rerun QUICK TEST and CYLINDER BALANCE TEST. If test light does not glow dimly, perform the following procedure. No Light - Check for 12 volts at test pins No. 37 and 57. Bright Light - Check injector circuit for shorts to ground. If okay, remove breakout box and replace ECA. Rerun QUICK TEST.
7. Fuel Pressure Problems: External Sources. Pressurize fuel system as per step 1). Examine fuel system in the following manner. MPFI Engines - Visually inspect, fuel injector "O" rings, fuel pressure regulator, and fuel rails. CFI Engines - Remove air inlet duct at fuel charging assembly injection inlet. Visually inspect, fuel injector "O" rings, fuel pressure regulator, and fuel line connections. If there is a visible leak, remove pressure gauge. Repair leak as necessary. Rerun QUICK TEST. If there is no leak, go to next step for MPFI engines. For CFI engines, remove pressure gauge. Fuel delivery system is okay. Problem is in common area for all cylinders, such as, vacuum leak, fuel contamination, or EGR leak.
8. Injector Balance Test. Connect tachometer to engine. Start and run engine at idle. Disconnect and reconnect injectors one at a time. Note RPM drop for each injector. Each injector should produce a momentary RPM drop of about 100 RPM drop. Note that ISC will attempt to re-establish correct RPM. If each injector does not produce at least 100 RPM drop when disconnected, service or replace faulty injector(s) and repeat QUICK TEST. If RPM drop is correct for all injectors, fuel delivery is okay. Problem is in area common to all cylinders such as a vacuum leak, fuel contamination, EGR, etc.
9. Cylinder Balance Test: SEFI Engines ONLY. Perform KOER SELF-TEST. After last code is displayed, wait 5-10 seconds. Enter CYLINDER BALANCE TEST by briefly opening throttle for one second (not WOT). Test time is approximately 2-3 minutes. A Code 77 indicates that the throttle was touched when the test was running and that the test was not completed. Use table to interpret codes received from test. If balance test does not display code 90, go to step 4). If balance test displays Code 90 (Pass), fuel delivery is okay, fault is in an area common to all cylinders (except SEFI MA vehicles). If a Code 42 or 92 is displayed, go to step 22). CYLINDER BALANCE TEST SERVICE CODES Service Code Cylinder or Injector No. Breakout Box Test Pin No. 90 (Pass) (Pass) 10 1 58 20 2 59 30 3 12 40 4 13 50 5 14 60 6 15 70 7 42 80 8 52 77 (Retest) (Retest) NOTE: A Code 90 received in the initial stage of the cylinder balance test indicates that the injector harness is not open or shorted, and a signal is being sent to all injectors.
10. Code 41 Or 91: Fuel Control Always Lean. If vehicle is equipped with dual HEGO's, Code 41 refers to the Right, or No. 1 HEGO and Code 91 refers to the Left, or No. 2 HEGO. Run engine at 2000 RPM for 2 minutes. Turn key off and wait 10 seconds. Rerun KOER SELF-TEST. Check for Code 41 or 91. If Code 41 or 91 is not displayed, go to step 19). If Code 41 and 91 is displayed, go to appropriate step number as listed below. Engines equipped with MAP sensors: Go to next step. Engines equipped with VAF meters: Go to step 12). Engines equipped with MA meters: Go to step 13).
11. Checking HEGO Sensor on Engines With MAP Sensors. Turn key off and set DVOM on 20-volt scale. Disconnect appropriate HEGO sensor from vehicle harness. Connect DVOM to HEGO SIGNAL lead at sensor and engine ground. Apply 10-14 in. Hg vacuum to Manifold Absolute Pressure (MAP) sensor and start engine. Run engine at 2000 RPM for 2 minutes. If reading is less than 0.5 volt, replace HEGO sensor(s) and then repeat QUICK TEST. If reading is greater than 0.5 volt, go to step 14). If reading is less than 0.5 volt, replace HEGO sensor, reconnect MAP, and rerun QUICK CHECK. NOTE: Vacuum or air leaks in non-EEC-IV related areas may cause Code 41 or 91. Check the following areas: A/C control motor, engine seals, EGR system, PVC system and lead contamination of HEGO sensor.
12. Checking HEGO Sensor on Engines With VAF meters. With key off and DVOM set on 20-volt scale, disconnect HEGO sensor from harness. Connect DVOM between HEGO sensor and engine ground. Remove air cleaner in order to reach airflow meter inlet. Use a pencil to prop air meter door in partially open position. Start and run engine at 2000 RPM for 2 minutes. If reading is not greater than 0.5 volt after one minute, replace HEGO sensor and repeat QUICK TEST. If reading is greater than 0.5 volt after one minute, go to step 14).
13. Checking HEGO Sensor on Engines With MA Sensor. The purpose of this test is to verify HEGO sensor can generate a voltage signal of greater than 0.5 volt during KOER SELF-TEST. With key off and DVOM set on 20-volt scale, disconnect HEGO sensor from harness. Connect DVOM between HEGO SIGNAL and battery negative post. Rerun KOER SELF-TEST and monitor HEGO sensor voltage. If voltage is greater than 0.5 volt, go to next step. If voltage is less than 0.5 volt, replace HEGO sensor and rerun QUICK TEST.
14. Checking Continuity of HEGO Signal and Ground Circuits. Turn key off. Install breakout box, leaving ECA and HEGO disconnected. Set DVOM on 200-ohm scale and measure resistance between test pin No. 49 and battery negative post. Measure resistance between test pin No. 29 and HEGO SIGNAL at vehicle harness connector. For vehicles with dual HEGO sensors, measure resistance between test pin No. 43 and HEGO SIGNAL at vehicle harness connector. If all readings are greater than 5 ohms, repair open in appropriate circuit, connect HEGO sensor and ECA, and repeat QUICK TEST. If all readings are less than 5 ohms, go to next step.
15. Checking HEGO Circuit For Short to Ground. Turn key off. Leave breakout box installed and ECA disconnected. Disconnect HEGO sensor and set DVOM on 200K-ohm scale. Measure resistance between test pin No. 29 and test pin No. 40 at the breakout box. For vehicles with dual sensors measure resistance between test pin No. 43 and test pin No. 40. If any reading is less than 10K ohms, repair short to ground. Repeat QUICK TEST. If reading is 10K ohms or more, go to next step. On models with 2.3L TC MPFI, go to step 18).
16. Checking HEGO Sensor For Short to Ground. With key off, breakout box installed, and ECA disconnected, set DVOM to 200K-ohm scale. Disconnect HEGO sensor. Measure resistance between PWR GND and HEGO SIGNAL at the HEGO sensor connector. If resistance is less than 10K ohms, replace HEGO sensor and rerun QUICK TEST. If resistance is greater than 10K ohms, do the appropriate following procedure. Engines equipped with MAP sensor: Go to next step. Engines equipped with VAF meter: Go to step 18). Engines equipped with MA (Mass Air Sensor): Remove breakout box, reconnect HEGO sensor, replace ECA and rerun QUICK TEST.
17. Eliminating Code 41: Engines With MAP Sensor. Turn key off. Install breakout box and connect ECA and HEGO sensor. Ensure MAP sensor vacuum hose is disconnected and plugged. Apply 10-14 in. Hg to MAP sensor. Start and run engine at 2000 RPM for 2 minutes. Allow engine to return to idle. Perform KOER SELF-TEST. If Code 41 is still present, check ECA connector for corroded or damaged pins. If connector is okay, replace ECA. Connect MAP sensor vacuum hose and repeat QUICK TEST. If Code 41 is not present, connect MAP sensor vacuum hose. HEGO input circuit is okay. Return to step 1).
18. Eliminating Code 41: Engines With VAF Meter. With key off, install breakout box and connect ECA. Reconnect HEGO sensor. Remove air filter and insert a pencil in VAF meter inlet. Start engine and run at 2000 RPM for approximately 2 minutes. Rerun SELF-TEST. If Code 41 is not present, the HEGO circuit is okay, Remove breakout box, reconnect ECA and go to step 1) of this test. If Code 41 is displayed, remove test set-up, replace ECA, and rerun QUICK TEST.
19. Checking Resistance of HEGO Heating Element. Turn key off, disconnect HEGO sensor, and set DVOM on 200-ohm scale. Measure resistance between KEY POWER circuit and POWER GROUND circuit at HEGO connector. Hot to warm resistance should be 5-20 ohms. Room temperature resistance is 2-5 ohms. If resistance is within specification, go to next step. If resistance is not within specifications, replace HEGO sensor and rerun QUICK TEST.
20. Checking Power at HEGO Harness Connector. With KOEO, and HEGO disconnected, set DVOM on 20-volt scale. Measure voltage between KEY POWER circuit and POWER GROUND circuit at HEGO harness connector. If voltage is greater than 10.5 volts, HEGO system is okay, go to step 1) of this test. If voltage is less than 10.5 volts, go to next step.
21. Checking Continuity of Power Ground Circuit. Turn key off and wait 10 seconds. Disconnect HEGO sensor and set DVOM on 200-ohm scale. Measure resistance between POWER GROUND circuit at HEGO vehicle harness connector and battery negative post. If resistance is less than 5 ohms, repair open in KEY POWER circuit and rerun QUICK TEST. If resistance is more than 5 ohms, reconnect HEGO sensor and repair open in POWER GROUND circuit. Rerun QUICK TEST.
22. Code 42 or 92: Fuel Control Rich, Check HEGO SIGNAL For Short To Power. On dual HEGO systems, Code 42 refers to right side HEGO, Code 92 refers to left side HEGO. Turn key off and wait 10 seconds. Disconnect appropriate HEGO sensor. Set DVOM on 20-volt scale. With KOEO, measure voltage between HEGO SIGNAL and POWER GROUND at HEGO harness connector. If reading is more than.5 volt, repair short to power in HEGO circuit. Repeat QUICK TEST. If reading is less than 0.5 volt, go to next step.
23. Checking HEGO Sensor For Short to Key Power Circuit. Turn key off and leave HEGO disconnected. Set DVOM on 200K-ohm scale. Measure resistance from KEY POWER circuit to HEGO SIGNAL circuit at HEGO sensor connector. If reading is 10K ohms or less, replace HEGO sensor and repeat QUICK TEST. If reading is greater than 10K ohms, go to next step.
24. Attempt to Generate Code 41 or 91. The following non-EEC areas may cause these codes: fuel contaminated engine oil, ignition misfire and faulty CANP system. Turn key off and wait 10 seconds. Disconnect appropriate HEGO sensor. Using jumper wire, connect HEGO SIGNAL circuit at HEGO harness connector to battery negative terminal. Repeat KOER SELF-TEST. If Codes 41 or 91 are present, remove jumper wire and go to next step for engines with MAP. All others, go to step 27). If codes 41 or 91 are not present, remove jumper wire. Disconnect ECA connector and inspect for damage. If connector is okay, replace ECA. Repeat QUICK TEST. NOTE: Because the MAP sensor has a large influence on fuel control, a Code 42 or 92 may be the result of a faulty MAP sensor, even though a Code 22 has not been set. The next 2 test steps will verify the MAP vacuum circuit.
25. Checking MAP Sensor For Vacuum Leaks. Turn key off and wait 10 seconds. Disconnect vacuum hose from MAP sensor and connect vacuum pump to sensor. Apply 18 in. Hg of vacuum to MAP sensor. If sensor does not hold vacuum, replace MAP sensor. Connect vacuum hose and repeat QUICK TEST. If MAP holds vacuum, release vacuum and go to next step.
26. Checking For Loss of Vacuum to MAP Sensor. Using vacuum "T", connect vacuum gauge in intake manifold vacuum hose at MAP sensor. Start engine and note vacuum reading. Turn key off and wait 10 seconds. Remove "T" and vacuum gauge. Reconnect hose to MAP sensor. Connect vacuum gauge at a different intake manifold location. Start engine and note vacuum reading. If readings differ by more than one in. Hg, inspect vacuum hoses for leaks, kinks, or blockage. Repair as required. If readings are within one in. Hg of each other, go to next step.
27. HEGO Sensor Check. Turn key off and wait 10 seconds. Disconnect HEGO sensor. Set DVOM on 20-volt scale and connect to HEGO SIGNAL at HEGO sensor connector. Remove a vacuum hose to create a vacuum leak, which will cause the HEGO sensor to go lean. Create a vacuum leak in the following manner: 2.3L Turbo MPFI Engines: Disconnect the manifold vacuum hose as illustrated. MA SEFI Engines: Disconnect any vacuum hose from the manifold vacuum "T". All Other Engines: Disconnect the PCV valve hose from the PCV valve. Start engine and run at 2000 RPM. The DVOM should indicate 0.4 volt within 30 seconds. If voltage is within specification, HEGO is okay, go to step 1) of this test. If voltage is not within specification, replace HEGO sensor and rerun QUICK TEST. (Scheme 85): 2.3L Turbo MPFI Engines: Induced Vacuum Leaks.
28. Continuous Memory Code 41 or 91. Indicates that a HEGO circuit has not switched during closed loop fuel control. In this situation a Code 41 or 91 may not indicate a lean condition. Diagnose all other driveability complaints in the DIAGNOSIS BY SYMPTOM test before attempting to service a Continuous Memory Code 41 or 91. Check the following areas. Unmetered Air/Vacuum Leaks Canister Purge System PVC System Engine Sealing Crimped Fuel Lines Plugged Fuel Filter Fouled Injectors HEGO Fuel Fouled If an over-rich condition is suspected of fouling the HEGO sensor, run the vehicle at sustained high (legal) speeds followed by a few hard acceleration runs. This will allow the HEGO contamination to be burned off. Ignition System Check for DEFAULT base timing in QUICK TEST procedure. Improper Fuel Used Lead Fouled HEGO Sensor. Fuel Pressure Check Pressure Using Steps 1) and 2). TP Sensor With KOEO, move throttle slowly to WOT. Measure voltage between test pins No. 47 and 46 at breakout box. If voltage does not increase with throttle opening, replace TP sensor or linkage as necessary. If vehicle still has driveability problems, perform test steps 3) through 6).
29. Continuous Memory Codes 41, 42, 43, 65, 85 or 86. Diagnose all other driveability complaints before servicing these codes. Code 41: HEGO indication that the fuel system was lean for more than 15 seconds when the fuel system should have been in closed loop fuel control. Code 42: HEGO indication that the fuel system was rich for more than 15 seconds when the fuel system should have been in closed loop fuel control. Code 43: HEGO indicated that the fuel system was lean during WOT for more than 3 seconds. Code 65: Closed loop not activated on HEGO switching. Code 85: Excessive rich mixture condition corrected by adaptive fuel strategy. Code 86: Excessive lean fuel mixture condition corrected by adaptive fuel strategy. If an over-rich fuel condition is suspected or experienced, check ignition system. Burn off fuel deposits on HEGO by operating the vehicle at sustained high (legal) speeds followed by a few hard acceleration runs. This will allow the HEGO contamination to be burned off. Check the following areas: Code 41: Intermittent HEGO signal (Signal or Ground circuit). If Code 65 also present, repair faulty HEGO circuit (Signal or Ground circuit). If Code 43 also present, service Code 43 first. Check VAF for leaks or sticking (caused by contamination or frost). Low fuel pressure at WOT, check fuel supply. Low fuel flow at WOT (pressure okay), check clogged injectors or low battery voltage. Code 42: Intermittent HEGO signal (Signal or Ground circuit). Airflow meter indicating incorrect airflow, check for high voltage output due to sticking air vane ("flapper door"). Excessive fuel flow, pressure regulator vacuum supply disconnected or blocked fuel return line. Excessive fuel flow, damaged or stuck open injector(s). Codes 41 and 42: Intermittent HEGO signal (Signal or Ground circuit). Sticking air vane ("flapper door"), due to contamination. Contaminated HEGO sensor, lead or silicone fouled. Code 43: Low fuel pressure at WOT, fuel pump or restricted supply. Low fuel flow at WOT, injectors plugged or low battery voltage (less than 11 volts). Code 65: Check for faulty HEGO signal (Signal or Ground circuit). Code 85: If Code 42 also displayed, service it first. Excessive fuel pressure, check regulator vacuum line and fuel supply line. Excessive fuel flow, check for damaged injector pintles or injector stuck open. Code 86: If Code 41 also displayed, service it first. Low fuel pressure, low pressure pump or restricted fuel supply. Low fuel flow, clogged injectors or low battery voltage.

C2 - FUEL PUMP CIRCUIT (INERTIA SWITCH)

Note. Perform this test when Service Code 87, 95, or 96 is displayed during QUICK TESTS or when directed here by other test procedures.

Fuel Pump Circuit Wiring Diagrams (1 of 4). Scheme 86

Fuel Pump Circuit Wiring Diagrams (2 of 4). Scheme 87

Fuel Pump Circuit Wiring Diagrams (3 of 4). Scheme 88

Fuel Pump Circuit Wiring Diagrams (4 of 4). Scheme 89

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuel lines, fuel filters, throttle body, fuel pump or contaminated fuel.

Scheme 90

Scheme 91

1. No Fuel Pressure: Electrical Check. Install fuel pressure gauge. Cycle key from off to on several times to check if fuel pump runs. DO NOT crank engine. Pump should operate briefly each time key is on. If pump runs as indicated, service or replace fuel pump as necessary. If pump does not run as indicated, go to next step.
2. Checking For VPWR to ECA. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and reconnect ECA. With KOEO, set DVOM on 20-volt scale and measure voltage between test pins No. 37 and 40, and between test pins No. 57 and 60. If either reading is less than 10.5 volts, go to «A2 - VEHICLE BATTERY»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a2-vehicle-battery), step 1). If both readings are 10.5 volts or more, go to next step for 2.3L Turbo MPFI or step 5) for all others.
3. Checking Continuity Between Fuel Pump Relay and Fuse. With KOEO, install breakout box and reconnect ECA. Disconnect fuel pump relay. Disconnect fuel pump relay fuse (fuse No. 20). Set DVOM on 200 ohm scale. Measure resistance between the POWER-TO-PUMPS circuit of the relay and the relay side of the fuse holder. If the resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit between fuel pump relay and fuse. (Scheme 90): Fuel Pump Relay Terminal Identification
4. Check Voltage to Power-to-Pumps Circuit (2.3L Turbo MPFI). With KOEO, breakout box installed and ECA connected. Disconnect fuel pump circuit fuse (fuse No. 20). Reconnect fuel pump relay. Set DVOM on 20-volt scale. Measure voltage between chassis ground and power-to pump circuit at fuel pump relay while cranking engine. If reading is less than 8 volts, go to step 6). If reading is 8 volts or more, check the following: open in power-to-pump circuit, open in fuel pump and open in fuel pump ground circuit.
5. Check Voltage to Power-to-Pump Circuit. With KOEO, breakout box installed and ECA connected. Disconnect fuel pump circuit fuse (fuse No. 20). Reconnect fuel pump relay. Set DVOM on 20-volt scale. Measure voltage between chassis ground and power-to-pump circuit at fuel pump relay while cranking engine. If reading is less than 8 volts, go to step 6). If reading is 8 volts or more, check the following: open in power-to-pump circuit, open in fuel pump and open in fuel pump ground circuit.
6. Checking BATT+ Circuit to Fuel Pump Relay. Turn key on, leaving engine off. Leave breakout box installed and ECA connected, locate fuel pump relay. Set DVOM on 20-volt scale. Measure voltage between chassis ground and BATT+ circuit at fuel pump relay. If reading is less than 10.5 volts, repair open in BATT+ circuit between fuel pump relay and battery positive post. Repeat QUICK TEST. If reading is 10.5 volts or greater, go to next step for 2.3L Turbo MPFI. All others, go to step 11).
7. Code 87: Checking VPWR Circuit to Fuel Pump Relay. Code 87 indicates a fuel pump primary circuit failure. Possible causes for this fault are: inertia switch not reset or electrically open, faulty fuel pump relay, ECA or, open or shorted circuit. Turn key on, leaving engine off. Leave breakout box installed and ECA connected. Locate fuel pump relay. Set DVOM on 20-volt scale. Measure voltage between chassis ground and VPWR circuit (ignition start/run circuit on 2.3L HSC engines) at fuel pump relay. If reading is 10.5 volts or more, go to next step. If reading is less than 10.5 volts, ensure inertia switch is on. If inertia switch will not reset, replace switch. If switch is okay, repair open in VPWR circuit (ignition switch Start/Run circuit and fuel pump relay on 2.3L HSC engines) between EEC power relay and fuel pump relay. Repeat QUICK TEST.
8. Checking Fuel Pump Circuit Continuity. Turn key off and wait 10 seconds. Leave breakout box installed and ECA connected. With DVOM on 200-ohm scale, measure resistance between fuel pump circuit at pump relay and test pin No. 22 at breakout box. If reading is 5 ohms or more, repair open in fuel pump circuit. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
9. Checking For Short to Power. Disconnect ECA and fuel pump relay. With key on, and breakout box installed, set DVOM on 20-volt scale. Measure voltage between test pin No. 22 and battery negative terminal. If voltage is less than one volt, go to next step. If voltage is more than one volt, repair short circuit. Reconnect ECA and attempt to start vehicle. If vehicle fails to start, replace ECA. Rerun QUICK TEST.
10. Checking For Shorts to Ground. Turn key off. Leave breakout box installed and disconnect ECA. Disconnect fuel pump relay. With DVOM on 200K-ohm scale, measure resistance between test pin No. 22 and test pins No. 40 and 60. If reading is less than 10K ohms, repair short in fuel pump circuit. Repeat QUICK TEST. If reading is 10K ohms or more, go to next step.
11. Checking Voltage at Power-to-Pump Circuit. Leave breakout box installed and ECA disconnected. Install a jumper wire between test pin No. 22 and test pins No. 40 or 60. Set DVOM on 20-volt scale. With KOEO, measure voltage between chassis ground and power-to-pump circuit at fuel pump relay. If reading is 10.5 volts or more, replace ECA and repeat QUICK TEST. If reading is less than 10.5 volts, replace fuel pump relay. Connect ECA and repeat QUICK TEST.
12. Code 95: Check Inertia Switch. A KOEO code 95 indicates that one of the following has occurred: Inertia switch not reset or electrically open. Open circuit in or between ECA and fuel pump. Faulty ground connection at fuel pump. Fuel pump secondary circuit shorted to power. Fuel pump relay contacts always closed. Faulty ECA. Turn key off and wait 10 seconds. Locate and disconnect inertia switch. Set DVOM on 200-ohm scale. Measure resistance of inertia switch. If resistance is less than 5 ohms, reconnect inertia switch and go to next step. If resistance is more than 5 ohms, replace or reset inertia switch and rerun QUICK TEST.
13. Verifying Fuel Pump is Off. With key off, listen for fuel pump noise. If fuel pump is off, go to step 15). If fuel pump is on, go to next step.
14. Fuel Pump Relay Check. Turn key off. Remove fuel pump relay. If fuel pump turns off, replace fuel pump relay. Repeat QUICK TEST. If fuel pump does not turn off, repair short to power-to-pump circuit. Repeat QUICK TEST.
15. Checking Continuity of Fuel Pump Monitor (FPM) Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and leave ECA disconnected. Disconnect fuel pump relay. Set DVOM on 200-ohm scale and measure resistance between test pin No. 8 at the breakout box and power-to-pump circuit at the fuel pump relay harness. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit and rerun QUICK TEST. (Scheme 91): Fuel Pump Relay Vehicle Harness Connector
16. Checking Continuity Between FPM Circuit and Ground. Turn key off. Install breakout box and disconnect ECA. Disconnect fuel pump relay. Set DVOM on 200-ohm scale and measure resistance between test pin No. 8 at the breakout box and battery negative terminal. If resistance is less than 10 ohms, remove test set-up, reconnect fuel pump relay, replace ECA and rerun QUICK TEST. If resistance is more than 10 ohms, remove test set-up and check the following: open circuit in fuel pump, poor ground connection at fuel pump, or an open in power-to-pump circuit.
17. Checking Fuel Pump Primary Circuit For Short to Ground. Turn key off and wait 10 seconds. Install breakout box and disconnect ECA. Disconnect fuel pump relay and set DVOM on 200K-ohm scale. Measure resistance between test pins No. 22 and 40 at the breakout box. If resistance is greater than 10K ohms, remove test set-up. Replace ECA, and rerun QUICK TEST. If resistance is less than 10K ohms, remove test set-up. Repair short circuit and rerun QUICK TEST.
18. Code 96: Checking BATT+ to Fuel Pump Relay. Service code 96 indicates a fuel pump secondary circuit failure between the BATT+ supply and the FPM connection to the POWER-to-PUMP connection. Possible causes for this fault are; faulty fuel pump relay or ECA, open circuit. Turn key off and wait 10 seconds. Locate fuel pump relay. With the DVOM on 20-volt scale, measure voltage between BATT+ circuit at fuel pump relay and battery negative. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open circuit and rerun QUICK TEST.
19. Verifying Fuel Pump Operation. With key off, set DVOM on 20-volt scale. Connect DVOM between POWER-to-PUMP circuit at fuel pump relay and battery negative post. Check voltage while turning key to ON position (one second) and OFF position (10 seconds). Repeat cycle at least 5 times. If voltage is greater than 10.5 volts for approximately one second after key is turned to ON position, replace ECA and rerun QUICK TEST. If voltage is not to specification, inspect relay harness connector and if okay, replace fuel pump relay.
20. Checking Continuity of Power-to-Pump Circuit. Turn key off and disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and leave ECA disconnected. With DVOM on 200-ohm scale, measure resistance between test pin No. 8 at breakout box and POWER-to-PUMP circuit at relay harness connector. If resistance is less than 5 ohms, remove test set up, replace ECA, and rerun QUICK TEST. If resistance is more than 5 ohms, repair open circuit between FPM connecting splice and relay. Rerun QUICK TEST.
21. Continuous Code 95: Checking EEC-IV Harness. A continuous code 95 indicates that one of the following conditions has occurred intermittently: Open circuit in or between the fuel pump and FPM circuit at the ECA. Faulty ground circuit at the fuel pump. Start engine and perform WIGGLE TEST on harness assembly to fuel pump, and to pump ground circuit harness. Lightly tap inertia switch and pump to simulate road shock. Check for engine miss or stumble while performing test. With key off, check harness connectors for corrosion or damage. Isolate and repair any faults that are found, clear Code 95 and rerun QUICK TEST. If no fault is found, go to next step.
22. Checking FPM Circuit. Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and leave ECA disconnected. With KOEO, connect a test light between test pin No. 8 and test pin No. 37. With test light lit, perform WIGGLE test on FPM circuit between pump and monitor. Light should go out if fault is found during WIGGLE TEST. Isolate and repair any found faults, remove test set-up and rerun QUICK TEST. If no faults are found, go to next step.
23. Check For Short to Power. With KOEO, breakout box installed and ECA disconnected. Connect a test light between test pin No. 8 and test pin No. 40. Observe test light, perform WIGGLE test on FPM circuit and POWER-to-PUMP circuit. Lightly tap the fuel pump relay to simulate road shock. Light should go on when fault is found during WIGGLE TEST, indicating a short to power. Listen for sound of fuel pump turning on. Isolate and repair any found faults, remove test set up and rerun QUICK TEST. If no faults are found, fault is intermittent and cannot be duplicated at this time.
24. Continuous Code 96: Check For Code 87. If Code 87 is also present with Code 96, go to step 26). If code 87 is not displayed, go to next step.
25. Checking EEC-IV Harness. A continuous code 96 without an accompanying code 87 indicates one of the following occurred during vehicle operation: An open in the BATT+ circuit between the BATT+ and the fuel pump relay, relay contacts opened or open in the POWER-to-PUMP circuit from the fuel pump relay to the FPM splice. With engine running attempt to cause a miss or stumble while performing WIGGLE TEST on pump harness and connectors. With engine off, inspect all connectors for damage or corrosion. If a fault is found, isolate and repair it. Clear codes and rerun QUICK TEST. If no fault is found, fault may not be duplicated at this time. Clear memory codes, code 96 testing is complete.
26. Continuous Code 87: Checking EEC-IV Harness. A continuous Code 87 indicates the primary fuel pump circuit has failed during vehicle operation. Possible causes for this fault are; An open in the VPWR circuit between the EEC power relay and the fuel pump relay, open coil in fuel pump relay or open in fuel pump circuit. Faulty inertia switch. With engine running, attempt to cause a miss or stumble while performing WIGGLE TEST on VPWR circuit between EEC power relay and fuel pump relay. Wiggle fuel pump circuit harness (test pin No. 22) between ECA and the fuel pump relay. Lightly tap fuel pump relay to simulate road shock. With key off, inspect ECA 60-pin connector for damage or corrosion. If a fault is found, isolate and repair it. Rerun QUICK TEST. If no fault is found, fault may not be duplicated at this time.

D1 - EGR ON/OFF CONTROL

Note. Perform this test when Service Code 34 is displayed during QUICK TESTS or when directed here by other test procedures. Code 34 may be result of high volume exhaust vent system reducing backpressure. If this is suspected, perform test in well-ventilated area without exhaust vent connected.

EGR On/Off Circuit. Scheme 92

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: air or vacuum leaks, EGR flow restrictions or EGR valve.

1. Code 34: Enter Output State Check. KOER Code 34 indicates that with engine RPM above idle and stable, a specified RPM drop did not occur when EGR was cycled. Possible causes for this fault are: Faulty EGR On/Off control solenoid Faulty EGR solenoid Faulty EGR vent solenoid Faulty EVP sensor Faulty wiring harness Faulty ECA Manifold vacuum line blocked or leaking Use only VOM/DVOM, not diagnostic tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect negative DVOM lead to STO at SELF-TEST connector and positive lead to positive battery terminal. Jumper STI to SIGNAL RETURN at SELF-TEST connector. Rerun KOEO SELF-TEST until end of CONTINUOUS SELF-TEST code display (DVOM will read zero volts). Depress and release throttle and observe DVOM reading. If DVOM reading changes to a higher voltage, stay in OUTPUT STATE CHECK and go to next step. If DVOM did not show high voltage, depress throttle to WOT and release. If STO voltage does not go high, go to «D16 - OUTPUT STATE CHECK NOT FUNCTIONING»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d16-output-state-check-not) , step 1). Leave test equipment hooked up.
2. Checking Solenoid Electrical Operation. Set DVOM on 20 volt scale. Connect DVOM positive lead to VPWR circuit at EGR solenoid and negative lead to EGR output circuit. Depress and release throttle several times to cycle EGR solenoid output on and off. If output does not cycle on and off, remove STI jumper wire and go to step 5). If output cycles on and off, go to next step.
3. Checking Solenoid For Vacuum Cycling. Connect vacuum pump to solenoid vacuum supply port and vacuum gauge to output port of solenoid. Apply minimum vacuum of 6 in. Hg. Depress and release throttle several times to cycle EGR solenoid output while maintaining vacuum at supply port. Note gauge reading. If vacuum output does not cycle, replace EGR solenoid and repeat QUICK TEST. If vacuum output cycles, go to next step.
4. Checking Manifold Vacuum Lines. With vacuum lines disconnected at EGR solenoid, start engine. If vacuum is present, EEC system is not cause of problem. Check exhaust gas recirculation system. If vacuum is not present, correct vacuum source blockage or leak and repeat QUICK TEST.
5. Measuring Solenoid Resistance. Turn key off and wait 10 seconds. Disconnect EGR solenoid. Set DVOM on 200-ohm scale and measure solenoid resistance. If reading is less than 65 ohms or more than 110 ohms, replace EGR solenoid and repeat QUICK TEST. If reading is between 65 and 110 ohms, go to next step.
6. Checking VPWR Circuit. With KOEO, set DVOM on 20-volt scale. Measure voltage between VPWR circuit at EGR solenoid harness connector and battery ground. If reading is less than 10.5 volts, repair open in harness and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
7. Checking Continuity of EGR Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 35 at the breakout box and EGR circuit at harness connector. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
8. Checking Circuit For Short to Ground. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Disconnect EGR solenoid. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 35 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short to ground and repeat QUICK TEST. If all readings are 10K ohms or more, go to next step.
9. Checking For Short to Power Circuit. Turn key off and wait 10 seconds. Leave breakout box installed. Disconnect ECA and EGR solenoid. With DVOM on 200K-ohm scale, measure resistance between test pin No. 35 and test pins No. 37 and 57. If any reading is less than 10K ohms, repair short to power and repeat QUICK TEST. If code is still repeated, replace ECA. If all readings are 10K ohms or more, replace ECA and repeat QUICK TEST.

D2 - IDLE SPEED CTRL (DC MOTOR/IDLE TRACKING SW. ASSEMBLY & TPS)

Perform this test only when Codes 12, 13, 16, 17, 19, 23, 38, 53, 58, 63, 68, 71, 73, or 93 are displayed or when directed here by DIAGNOSIS BY SYMPTOM TEST. To prevent replacement of good components be aware that the following non-EEC related areas may be at fault: throttle stop screw out of adjustment, vacuum leaks, sticking throttle, or basic engine (valves, timing, etc.).

DC Motor/Idle Tracking Switch (ITS) & TPS Circuit (1 of 2). Scheme 93

DC Motor/Idle Tracking Switch (ITS) & TPS Circuit (2 of 2). Scheme 94

DC Motor Shaft Measurements. Scheme 95

1. Code 13: Checking DC Motor Operation. Code 13 indicates and error in idle speed control management. Engine did not return to a specified lower RPM prior to "Goose" test portion of Self-Test. Possible causes for this fault are; faulty DC motor, open or shorted ISC circuit, faulty ECA. Turn key off and wait 10 seconds. Disconnect harness from DC motor. Using jumper wires, connect ISC positive (+) circuit of DC motor to battery positive (+) terminal and ISC negative (-) circuit of DC motor to battery negative terminal for 4 seconds. DC motor shaft should extend more than 2" (50 mm). See DC MOTOR SHAFT MEASUREMENTS illustration. Now connect ISC + circuit of DC motor to battery negative terminal and ISC- circuit of DC motor to battery positive terminal for 4 seconds. DC motor shaft should retract to less than 1 3/4" (44 mm). If DC motor shaft moves in and out as indicated, go to next step. If not, replace DC motor and repeat QUICK TEST.
2. Checking Continuity of ISC+ and ISC- Circuits. Turn key off and wait 10 seconds. Leave harness disconnected from DC motor. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 41 and ISC- circuit at harness connector and between test pin No. 21 and ISC+ circuit at harness connector. If both readings are less than 5 ohms, go to next step. If readings are 5 ohms or more, repair circuit(s) and repeat QUICK TEST.
3. Checking ISC+ and ISC- Circuits For Shorts To Ground. Turn key off and wait 10 seconds. Leave breakout box and ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 41 and test pins No. 40, 46 and 60. Also measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If all readings are greater than 10K ohms, go to next step. If any reading is less than 10K ohms, repair faulty circuit(s) and repeat QUICK TEST.
4. Checking ISC+ and ISC- For Shorts to PWR. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Disconnect DC motor from harness. Set DVOM to 20 volt scale. Measure voltage between test pin No. 41 and test pins No. 40 and 60. Also measure voltage between test pin No. 21 and test pins No. 40 and 60. If all readings are less than one volt, replace ECA and repeat QUICK TEST. If any reading is more than one volt, repair faulty circuit(s) and repeat QUICK TEST.
5. Code 58: Check For Full Motor Retraction. Turn key off and wait 10 seconds. Disconnect DC motor from harness. Using jumper wires, connect DC motor ISC - circuit to battery positive (+) terminal and ISC positive (+) circuit to battery negative (-) terminal for 4 seconds. DC motor shaft should be fully retracted, away from throttle lever. If shaft is retracted, go to step 7). If shaft does not retract, go to next step.
6. Measuring Motor Retraction. Turn key off and wait 10 seconds. Disconnect DC motor from harness. Ensure DC motor is fully retracted. Measure distance from DC motor mounting bracket to tip of motor shaft. See DC MOTOR SHAFT MEASUREMENTS. If DC motor shaft is retracted to less than 1 3/4" (44 mm), reconnect DC motor. Check throttle stop adjustment. If DC motor shaft does not retract, replace DC motor and repeat quick test.
7. Checking Idle Tracking Switch (ITS). Turn key off and wait 10 seconds. Disconnect DC motor from harness. Ensure DC motor is fully retracted and not touching throttle lever. Set DVOM on 200-ohm scale. Measure resistance between ITS circuit and SIG RTN at DC motor connector. If reading is less than 5 ohms, go to next step. If not, replace DC motor and repeat QUICK TEST.
8. Checking Continuity of ITS & SIG RTN Circuits. Turn key off and wait 10 seconds. Disconnect DC motor from harness. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and SIG RTN circuit at DC motor harness connector. Also measure resistance between test pin No. 28 at the breakout box and ITS circuit at DC motor harness connector. If both readings are less than 5 ohms, reconnect DC motor. Replace ECA and repeat QUICK TEST. If any reading is 5 ohms or more, reconnect DC motor. Repair open circuit(s) and repeat QUICK TEST.
9. Code 68: Checking Idle Tracking Switch. Code 68 indicates DC motor shaft is in contact with throttle lever when DC motor signal was produced to retract shaft. Possible causes for this fault are: faulty DC motor, short to ground in ITS circuit or faulty ECA. Turn key off and wait 10 seconds. Disconnect DC motor from harness. Set DVOM on 200-ohm scale. Measure resistance between ITS circuit and SIG RTN circuit at DC motor connector. If all readings are greater than 5 ohms, go to next step. If any reading is 5 ohms or less, replace DC motor and repeat QUICK TEST.
10. Checking ITS For Shorts To Ground. Turn key off and wait 10 seconds. Disconnect DC motor from harness. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Connect breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 28 and test pins No. 40, 46, and 60. If all readings are greater than 10K ohms, reconnect DC motor. Replace ECA and repeat QUICK TEST. If any reading is 10K ohms or less, reconnect DC motor. Repair faulty circuit(s) and repeat QUICK TEST.
11. Code 93: Checking Throttle Linkage. Code 93 indicates a fault between DC motor a throttle linkage. Turn key off and wait 10 seconds. Inspect throttle for freedom of movement to wide open throttle and for damaged or bent throttle lever. If throttle lever and linkage are okay, replace DC motor and repeat QUICK TEST. If throttle lever and/or linkage are damaged, repair as necessary and repeat QUICK TEST.
12. Code 23: Checking Throttle Plate Closing. Code 23 indicates throttle plate is not in correct position during Self-Test. Possible causes for this fault are: a faulty TPS, open in TPS circuit, or a faulty ECA. Perform KOEO SELF-TEST. Disconnect DC motor when shaft is fully retracted. Turn key off and wait 10 seconds. Remove air cleaner from throttle body. Inspect throttle for freedom of movement and for proper closing of throttle valves. If throttle moves freely and closes without obstructions, reconnect DC motor and go to next step. If throttle binds or does not close properly, repair as necessary and repeat QUICK TEST.
13. Checking Voltage Of VREF to SIG RTN. Turn key off and wait 10 seconds. Disconnect TPS harness connector at throttle body. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between VREF and SIG RTN at TPS harness connector. If reading is between 4-6 volts, reconnect TPS and go to next step. If reading is incorrect, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1).
14. Checking Throttle Stop RPM. Perform KOEO SELF-TEST. Disconnect DC motor after shaft has fully retracted and exit SELF-TEST. Start engine and verify that throttle stop RPM is less than curb idle speed. If throttle stop RPM is set to less than curb idle speed, replace TPS. Connect DC motor and repeat QUICK TEST. If throttle stop RPM is not less than curb idle speed, adjust throttle stop RPM. Connect DC motor and repeat QUICK TEST.
15. Code 53: Generate Code 63. Code 53 indicates TPS output signal is greater than the Self-Test maximum of 4.7 volts. Possible causes for this fault are: faulty TPS, faulty ECA or short to power in TPS circuit. Turn key off and wait 10 seconds. Disconnect harness from TPS at throttle body. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Perform KOEO SELF-TEST and record codes. If Code 63 is displayed, go to next step. If Code 63 is not displayed, go to step 17). Ignore all other codes.
16. Check Voltage at VREF to SIG RTN. Turn key off and wait 10 seconds. Disconnect TPS harness at throttle body. Set DVOM on 20 volt scale. Turn key on, leaving engine off. Measure voltage between VREF and SIG RTN at TPS harness connector. If reading is 4-6 volts, replace TPS and repeat QUICK TEST. If not, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1).
17. Check TP Signal For Short To Power. Turn key off and wait 10 seconds. Disconnect TPS harness at throttle body. Set DVOM on 200K ohm scale. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Measure resistance between test pin No. 47 and test pins No. 26 and 57 at breakout box. If both readings are 10K ohms or greater, replace ECA and repeat QUICK TEST. If any reading is less than 10K ohms, repair faulty circuit(s) and repeat QUICK TEST.
18. Code 63: Generate Service Code 53. Code 63 indicates TP signal is less than Self-Test minimum of 0.2 volt. A failure mode signal indicates a closed throttle to the ECA. Possible causes for this fault are: a faulty TPS or ECA, open in TPS circuit or short to ground in TPS. Turn key off and wait 10 seconds. Disconnect TPS harness at throttle body. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Using jumper wire, connect VREF to TP signal at TPS harness connector. Perform KOEO SELF-TEST. If no codes are displayed, immediately remove jumper wire and go directly to step 21). If Code 53 is displayed, replace TPS sensor and repeat QUICK TEST. If Code 53 is not displayed, go to next step. Ignore all other codes at this time.
19. Voltage Check: VREF to SIG RTN. Turn key off and wait 10 seconds. Disconnect TPS harness at throttle body. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between VREF and SIG RTN at TPS harness connector. If reading is between 4-6 volts, go to next step. If not, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1).
20. Checking Continuity of TP Signal Circuit. Turn key off and wait 10 seconds. Disconnect TPS harness at throttle body. Set DVOM on 200-ohm scale. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Measure resistance between TPS signal at harness connector and test pin No. 47 at breakout box. If reading is less than 5 ohms, go to next step. If not, repair circuit. Reconnect TPS harness and repeat QUICK TEST.
21. Checking TP Signal For Short To Ground. Turn key off and wait 10 seconds. Disconnect TPS harness at throttle body. With breakout box installed and ECA disconnected, set DVOM on 200K-ohm scale. Measure resistance between TP signal at harness connector and test pins No. 40, 46, and 60 at breakout box. If all readings are greater than 10K ohms, replace ECA. Connect TPS and repeat QUICK TEST. If any reading is less than 10K ohms, repair faulty circuit(s) and repeat QUICK TEST.
22. Code 73: Displayed. Code 73 indicates ECA did not detect sufficient change in throttle position during "Goose" test. Possible causes for this fault are: faulty TPS or sensor circuit, faulty EGR system, faulty EGO sensor or sensor circuit or faulty ITS circuit. Perform KOEO SELF-TEST. If Code 73 is still displayed in KOEO SELF-TEST, replace TPS and repeat QUICK TEST. If Code 73 is not displayed, repair other codes.
23. Code 12: Check For Codes That Could Cause Code 12. Code 12 indicates system is not capable of raising engine speed above curb idle. Perform KOER SELF-TEST. If Codes 31, 32, 34, 35, 41, or 58 are displayed, repair these codes first. See KOER SELF-TEST table for instructions. If these codes are not displayed, go to next step.
24. Check For Sticking Throttle Linkage. Check throttle plates and linkage for binding. Check cruise control linkage for proper adjustment. If throttle opens and closes properly, go to next step. If throttle does not operate properly, repair throttle as required and repeat QUICK TEST.
25. Checking DC Motor Operation. Turn key off and wait 10 seconds. Disconnect harness from DC motor. Ensure other pins are not shorted when connecting jumper to ISC connector. Using jumper wires, carefully connect ISC positive (+) circuit of DC motor to battery positive (+) terminal and ISC negative (-) circuit of DC motor to battery negative terminal for 4 seconds. DC motor shaft should extend more than 2" (50 mm). See DC MOTOR SHAFT MEASUREMENTS illustration. Now connect ISC positive (+) circuit of DC motor to battery negative (-) terminal and ISC negative (-) circuit of DC motor to battery positive (+) terminal for 4 seconds. DC motor shaft should retract to less than 1 3/4" (44 mm). If DC motor shaft moves in and out as indicated, replace ECA and repeat QUICK TEST. If not, replace DC motor and repeat QUICK TEST.
26. Code 13 or 19: Erratic Idle Check. Code 13 or 19 indicates that the engine does not remain at a specified lower RPM prior to entering the "Goose" test portion of the Self-Test. Possible causes for this fault are; faulty MAP/BP sensor, faulty EGR sensor or circuit, faulty EGO sensor or circuit, faulty ITS. Ensure engine is at normal operating temperature. Deactivate SELF-TEST. Ensure A/C is off (if equipped). Start and run engine for 3 minutes, alternating between 30 second idle and 5 second part throttle operation. If idle is erratic, go to next step. If idle is not erratic at end of 3 minute idle/part throttle test, go to step 28).
27. Check For Additional Codes During KOER SELF-TEST. Check for vacuum leaks, and Codes 22, 31, 32, 34, 35, 41, or 58. Repair these codes before going on to next step.
28. Checking Throttle Plates and Linkage. Inspect throttle plates and/or linkage for binding. If throttle opens and closes properly, replace DC motor and repeat QUICK TEST. If throttle binds, repair throttle as required and repeat QUICK TEST.
29. Continuous Memory Code 99: Check ECA Operation. Code 99 indicates the ECA has not received enough information to control engine idle speed. Deactivate SELF-TEST and start engine. DO NOT touch the throttle. Allow engine to idle for 2 minutes and shut engine off. When key has been off 10 seconds, run KOEO SELF-TEST. After service codes are displayed, deactivate SELF-TEST. Turn key off and wait 10 seconds. Rerun KOER SELF-TEST. If Code 99 is displayed, replace ECA. If Code 99 is not displayed, service other service codes.
30. Code 16 or 17: Related Mechanical Problems. Code 16 may indicate that the accelerator pedal was touched during KOER SELF-TEST. Code 17 indicates an electrical load such as engine cooling fan or A/C compressor was activated during the SELF-TEST. Check engine for vacuum leaks, binding throttle linkage, base ignition timing, and throttle stop screw adjustment. If these items are okay, service other codes as necessary and rerun QUICK TEST. If a faulty item is found, service as necessary and rerun QUICK TEST.
31. Continuous Code 13 Displayed. Code 13 indicates that in the last 40 engine warm-up cycles, the Throttle Position Sensor (TPS) rotation did not follow the reaction of DC motor when idle speed control was in dashpot mode. This condition may be caused by the following: DC motor sticking at part throttle. An open in ITS circuit which, when coupled with other inputs to ECA, causes EEC system to falsely enter dashpot mode. TPS sticking at part throttle. Each of these areas may generate KOEO SELF-TEST Codes or Continuous Memory Codes. If repairs have been made for KOEO SELF-TEST Codes 13 or 58, Continuous Memory Code 13 can be considered serviced and erased from memory. If Continuous Memory Codes 13 and 38 are present, service Code 38 first. If these codes are not present, make the following checks: Go to step 1) of this test and check for FULL travel of DC motor shaft. Replace DC motor if travel is not obtained. Leave motor in FULL retract position. See DC MOTOR SHAFT MEASUREMENTS illustration. With motor in full retract position, and with ITS not touching throttle lever check for an open in ITS circuit. Turn key off and install breakout box. Make necessary connector/pin inspections. With DVOM on 200-ohm scale, monitor resistance between test pins No. 28 and 46 while tapping, wiggling, and bending DC motor connector and harness. DO NOT push in idle tracking switch. If DVOM reading changes from less than 5 ohms to more than 5 ohms, an open circuit exists in wiring. Repair as necessary. Check for binding TPS by monitoring TPS voltage while moving throttle from a wide open position to a closed throttle position. Install breakout box and make all necessary connector/pin inspections. Fully retract DC motor shaft by placing a jumper wire between test pins No. 41 and 57. When motor is fully retracted, disconnect it at harness and remove jumper wire from breakout box. Turn key on and set DVOM on 20-volt scale. Slowly move throttle to wide open and closed throttle positions. Readings should move from more than 4 volts to less than 1.5 volts. If voltage readings hang up in mid-range, showing zero to 1.5 volts, replace TPS. If readings are correct, TPS is okay, do not service.
32. Continuous Code 38 Displayed. Code 38 indicates that in the last 40 engine warm-up cycles the idle tracking switch was open (ITS touching throttle) when throttle angle was greater than the maximum extension of DC motor shaft. This condition could be caused by the following conditions: An open in ITS circuit. Idle tracking switch stuck in open (pushed in) position. These conditions may cause a Code 58 to appear in KOEO SELF-TEST. If repair has been made for Code 58, Continuous Memory Code 38 can be considered serviced, and erased from memory. If KOEO SELF-TEST Code 58 was not displayed, check the following: With DC motor fully retracted and ITS not touching throttle lever, check for an intermittent in ITS circuit. Turn ignition off and install breakout box. Make the necessary connector/pin inspections. With DVOM on 200-ohm scale, measure resistance between test pins No. 28 and 46 while tapping, wiggling, or bending DC motor connector and harness. DO NOT push in idle tracking switch. If DVOM reading changes from less than 5 ohms to more than 5 ohms, an open circuit exists in wiring. Repair as necessary.
33. Continuous Code 71 Displayed. This code indicates that in the last 40 engine warm-up cycles the idle tracking switch was closed (ITS not touching throttle lever) when DC motor was in preset position. This condition can be caused by the following: ITS circuit shorted to ground or SIG RTN. ITS stuck in closed position (NOT in pushed in position). Either of these conditions may cause KOEO SELF-TEST Code 68. If repairs have been made for Code 68, Continuous Memory Code 71 can be considered serviced and erased from memory. If Code 68 was not displayed, check the following: Check ITS circuit for an intermittent short to ground or SIG RTN. Turn key off. Enter KOEO CONTINUOUS MONITOR (WIGGLE) TEST and systematically tap, wiggle, or bend harness while looking for indication of fault. If fault is created, repair as necessary. Due to nature of this test step, Code 71 will NOT reappear in memory if fault is found.
34. Continuous Code 53 Displayed. Code 53 indicates TPS sensor output signal was greater than the 4.7 volt Self-Test maximum. The failure mode sends a WOT signal to the ECA. Possible causes for this fault are: faulty TPS or faulty ECA, short to power in TPS circuit. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault, while slowly moving throttle slowly to WOT. Slowly release throttle to closed position and lightly tap on TPS to simulate road shock and lightly wiggle TPS harness connector. If fault is indicated, go to next step. If not, go to step 36).
35. Throttle Position Signal Voltage. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box and connect ECA. Set DVOM on 20-volt scale. Connect DVOM from test pin No. 47 to test pin No. 46. Turn key on, leaving engine off. While observing DVOM, move throttle slowly to closed position and lightly tap on TPS. Wiggle TPS harness and connector. If fault occurs at less than 4.25 volts, disconnect and inspect connectors. If okay, replace TPS and repeat QUICK TEST. If fault occurs at greater than 4.25 volts, TPS overtravel may have caused Code 53. Go to next step.
36. Checking EEC-IV Harness. Observe VOM or diagnostic tester for fault indication while grasping harness close to sensor connector. Wiggle, shake, or bend a small section of harness while working toward firewall. Repeat procedure from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. After repairs repeat QUICK TEST. If no fault occurs, go to next step.
37. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for obvious fault or damage. If connector and terminals are okay, fault cannot be duplicated at this time. Testing is complete. If connector or terminals are damaged, repair as necessary. After repairs, repeat QUICK TEST.
38. Checking Continuous Codes 23 or 63: Operate TPS. Code 23 or 63 indicates TPS output signal is less than the Self-Test minimum of 0.2 volt. Failure mode indicates closed throttle to the ECA. Possible causes for this fault are: faulty TPS, open or short to ground in TPS harness circuit or faulty ECA. Using KOEO CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while slowly moving throttle to WOT. Slowly release throttle to closed position, lightly tap on TPS to simulate road shock and lightly wiggle TPS harness connector. If fault is indicated, disconnect and inspect connectors. If connectors and terminals are okay, replace TPS and repeat QUICK TEST. If no fault is indicated, repeat test steps 36) and 37).

D3 - AIR MANAGEMENT SYSTEM (AM1/AM2)

Note. Perform this test when Service Codes 44, 45, 46, 81, 82 or 94 is displayed during QUICK TESTS or when directed here by other test procedures.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: thermactor air system drive belt, air pump or valve.

Air Management Circuits. Scheme 96

1. Codes 44 (94), 45 & 46: Verify Vacuum Line Routing. Code 44 or 94 indicates thermactor system is inoperative. Code 45 indicates thermactor air not flowing upstream when signaled to do so by ECA. Code 46 indicates thermactor air not by-passed when directed. Possible causes for these faults are: vacuum hoses leaking, blocked or kinked, diverter valve or thermactor pump inoperative or AM solenoid defective or blocked. Check for correct vacuum hose routing to AM1/AM2 solenoids and by-pass diverter valve. Use vehicle emissions label as a guide. Check for kinked or blocked vacuum hoses. Check for kinked or blocked air hoses. Check for disconnected vacuum hoses. If problems are detected, correct hose routing, repair faults and repeat QUICK TEST. If vacuum routing is okay, and Code 44 (94) is displayed, go to step 4). If Code 46 is displayed, go to step 3). If Code 45 is displayed, go to next step.
2. Eliminating Displayed Code 45 (AM2). This step checks AM2 solenoid only. Disconnect and plug vacuum hose at diverter valve. Turn key off and wait 10 seconds. Repeat KOER SELF-TEST and record codes. If Code 45 is displayed, EEC system is okay. Check diverter valve and/or check valve for problem. If Code 45 is not displayed, go to step 4).
3. Eliminating Displayed Code 46 (AM1). This step checks AM1 solenoid only. Disconnect and plug vacuum hose at by-pass valve. Turn key off and wait 10 seconds. Repeat KOER SELF-TEST and record codes. If Code 46 is displayed, EEC system is okay. Check by-pass valve for problem. If Code 46 is not displayed, go to next step.
4. Output Check. Enter OUTPUT STATE CHECK, see OUTPUT STATE CHECK, under DIAGNOSTIC AIDS. Use only DVOM, not diagnostic tester, for this step. Turn key off and wait 10 seconds. With DVOM on 20-volt scale, connect DVOM negative test lead to STO circuit at SELF-TEST connector and positive test lead to battery positive terminal. Using jumper wire, connect STI to SIG RTN at SELF-TEST connector. Perform KOEO SELF-TEST until end of CONTINUOUS SELF-TEST codes (DVOM reads zero volts). Depress and release throttle. DVOM should change to a high voltage reading. If reading changed, remain in OUTPUT STATE CHECK and go to next step. If reading did not change, depress throttle to WOT and release. If STO voltage does not go high, go to «D16 - OUTPUT STATE CHECK NOT FUNCTIONING»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d16-output-state-check-not) , step 1). Leave test equipment hooked up.
5. Checking AM1/AM2 Solenoid Operation. Set DVOM on 20-volt scale. Connect DVOM positive test lead to VPWR circuit and negative test lead to AM1 circuit at AM1 solenoid. While observing DVOM, depress and release throttle several times to cycle output on and off. Repeat for AM2 solenoid. Connect positive test lead to VPWR circuit and negative test lead to AM2 circuit at AM2 solenoid. Cycle AM2 solenoid on and off. If either solenoid does not cycle on and off, remove jumper and go to step 9). If both solenoids cycle on and off, go to next step.
6. Checking Solenoids For Vacuum Cycling. Connect vacuum pump to AM1 solenoid vacuum supply port. Connect vacuum gauge to output port. Maintain vacuum at source while depressing and releasing throttle to cycle output on and off. Observe vacuum gauge. Repeat for AM2 solenoid. If either output does not cycle on and off, replace solenoid assembly and repeat QUICK TEST. If both outputs cycle on and off, go to next step.
7. Checking Manifold Vacuum Lines. With vacuum hoses disconnected at AM1/AM2 solenoid assembly, start engine and check for vacuum. If vacuum is present, EEC system is okay. Check thermactor valve and air pump for problems. If no vacuum is present, repair blockage as required and repeat QUICK TEST.
8. Codes 81 and 82: Checking Voltage to VPWR Circuit. Code 81 and 82 indicates voltage output for thermactor air solenoid did not change when activated. Possible causes for this fault are: shorted or open circuits, solenoid resistance out of range or faulty ECA. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between AM1 solenoid VPWR circuit and battery ground. Repeat test for AM2 solenoid. If either voltage reading is less than 10.5 volts, repair harness circuit open and repeat QUICK TEST. If both readings are greater than 10.5 volts, go to next step.
9. Measuring Solenoid Resistance. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect AM1 and AM2 solenoid connectors. Measure resistance of both solenoids. If either reading is less than 50 ohms or more 100 ohms, replace solenoid assembly and repeat QUICK TEST. If both readings are between 50 and 100 ohms, connect TAB and TAD solenoids. Go to next step.
10. Checking Circuit Continuity. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box, leaving ECA disconnected. With DVOM on 200-ohm scale, measure resistance between test pin No. 51 and AM1 circuit at harness connector. Measure resistance between test pin No. 11 (No. 32 on 5.0L MA SEFI) and AM2 circuit at harness connector. If either reading is 5 ohms or more, repair harness open circuit and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.
11. Checking For Shorts to Ground. Turn key off and wait 10 seconds. Set DVOM on 200K-scale. Leave breakout box installed and ECA disconnected. Disconnect AM1/AM2 solenoids. Measure resistance between test pin No. 51 (No. 38 on 5.0L MA SEFI) and test pins No. 40, 46 and 60, and between test pin No. 11 (No. 32 on 5.0L MA SEFI) and test pins No. 40, 46 and 60. If any reading is less than 10K ohms, repair short to power. Remove breakout box, connect harness to ECA and repeat QUICK TEST. If all readings are 10K ohms or more, go to next step.
12. Checking For Shorts to Power Circuit. Turn key off and wait 10 seconds. Set DVOM on 200K-ohm scale. Leave breakout box installed with ECA and solenoids disconnected. Measure resistance between test pin No. 51 and test pins No. 37 and 57 and between test pin No. 11 (No. 32 on 5.0L MA SEFI) and test pins No. 37 and 57. If any reading is less than 10K ohms, repair short to power. Remove breakout box, connect harness to ECA and repeat QUICK TEST. If code is repeated, replace ECA. If all readings are 10K ohms or more, replace ECA and repeat QUICK TEST.

D4 - CANISTER PURGE (CANP)

Note. Perform this test when Service Code 85 is displayed during QUICK TESTS or when directed here by other test procedures.

Canister Purge (CANP) Circuit. Scheme 97

1. Checking System Function. Enter OUTPUT STATE CHECK see OUTPUT STATE CHECK, under QUICK TEST DIAGNOSTIC AIDS. Use only DVOM, not diagnostic tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO and positive test lead to positive battery terminal. Using jumper wire, connect STI circuit to SIGNAL RETURN at SELF-TEST connector. Perform KOEO SELF-TEST until end of Continuous Memory Codes (DVOM reads zero volts). Depress and release throttle. DVOM should change to a high voltage reading. If reading did not change, depress throttle to WOT and release. If STO voltage does not go high, go to «D16 - OUTPUT STATE CHECK NOT FUNCTIONING»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d16-output-state-check-not) , step 1). Leave test equipment hooked up. If reading changed, remain in OUTPUT STATE CHECK and go to next step.
2. Checking Solenoid Electrical Function. With KOEO, set DVOM on 20-volt scale. Disconnect CANP solenoid. Connect DVOM positive test lead to VPWR circuit and negative test lead to CANP output circuit on harness connector. While observing DVOM, depress and release throttle several times to cycle output on and off. If CANP circuit does not cycle on and off, remove jumper wire and go to step 6). If CANP circuit cycles, go to next step.
3. Checking Solenoid For Vacuum Leaks. Turn key on. Leave CANP solenoid disconnected. Disconnect vacuum hose at canister purge solenoid from manifold vacuum side of engine. Apply 16 in. Hg vacuum to manifold vacuum side of CANP solenoid. If CANP solenoid does not hold vacuum for 20 seconds, replace it and repeat QUICK TEST. If fault is still present, service fuel evaporation canister. If CANP holds vacuum for 20 seconds, leave vacuum pump attached and go to next step.
4. Checking Solenoid Mechanical Operation. While still in OUTPUT STATE CHECK, cycle CANP circuit off (no voltage). Reconnect CANP solenoid connector. Apply 16 in. Hg vacuum to CANP solenoid as in step 3). Depress and release throttle. If vacuum is released, check hose from solenoid to canister for leaks or cracks, if okay, remove jumper wire from STI and go to next step. If vacuum is not released, replace CANP solenoid and repeat QUICK TEST.
5. Checking Vacuum Supply. Disconnect vacuum hose from canister purge solenoid on manifold vacuum (PVC) side. Start engine. If vacuum is present at vacuum hose, EEC system is okay. Check evaporative canister. If vacuum is not present at hose, check vacuum hose for proper routing, kinks, or blockage, If okay, check engine for cause of low vacuum.
6. Measuring CANP Solenoid Resistance. Code 85 indicates a fault in the CANP solenoid circuit. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect CANP solenoid connector and measure solenoid resistance. If reading is between 40-90 ohms, go to next step. If reading is incorrect, replace CANP solenoid and repeat QUICK TEST.
7. Checking Voltage of VPWR Circuit. With KOEO, and CANP solenoid disconnected, set DVOM on 20-volt scale. Measure voltage between VPWR circuit at CANP solenoid harness connector and battery negative terminal. If reading is 10.5 volts or greater, go to next step. If reading is less than 10.5 volts, repair open in circuit and repeat QUICK TEST.
8. Checking Continuity of CANP Circuit. Turn key off and wait 10 seconds. Disconnect CANP solenoid and ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 31 and CANP harness connector. If reading is less than 5 ohms, go to next step. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.
9. Checking For Short to Ground. Turn key off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale and disconnect CANP solenoid. Measure resistance between test pin No. 31 and test pins No. 40, 46, and 60. If all readings are 10K ohms or more, go to next step. If any reading is less than 10K ohms, repair short to ground and repeat QUICK TEST.
10. Checking For Short to Power. Turn key off and wait 10 seconds. Disconnect CANP solenoid. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale and disconnect CANP solenoid. Measure resistance between test pin No. 31 and test pins No. 37 and 57. If all reading are 10K ohms or more, remove breakout box. Replace ECA and repeat QUICK TEST. If any reading is less than 10K ohms, repair short to power and repeat QUICK TEST. If code is repeated, replace ECA and repeat QUICK TEST.
11. Check If CANP Caused Codes 16 or 26. With key off, disconnect vacuum hose at canister purge solenoid on canister side. Start engine and allow to idle. If vacuum is present on canister side of canister purge solenoid, go to step 1), in this test. If vacuum is not present, and a Code 26 is displayed, check for vacuum leaks or lack of vacuum. If Code 16 is present, check for vacuum leaks at injector "O" rings, vacuum lines and fittings, or between air meter and throttle body. Service as necessary and rerun QUICK TEST.

D5 - IDLE SPEED CONTROL (AIR BY-PASS)

Note. Perform this test when Service Code 12, 13, 16, 17, 19, 47 or 48 displayed during QUICK TESTS or when directed here by other test procedures. If engine is running rough or has rough idle, correct these conditions before performing test. Causes may be in ignition system, fuel system or EGR system.

Idle Speed Control (Air By-Pass) Circuit. Scheme 98

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: engine temperature not up to operating temperature, engine over operating temperature, A/C input (electrical problem), improper idle speed/throttle stop adjustment or cruise control linkage.

Scheme 99

1. Code 12: Check For RPM Drop. Code 12 indicates that during KOER Self-Test engine RPM could not be controlled within Self-Test minimum RPM. Possible causes for this fault are: Open or shorted circuit. Sticking or binding throttle linkage. Incorrect idle adjustment. Throttle body or ISC solenoid contamination. Faulty ISC solenoid. Faulty ECA. Non-ECC mechanical faults. Turn key off. Connect engine tachometer and start engine. Disconnect Idle Speed Control (ISC) harness. If RPM drops or if engine stalls, go to next step. If not, go to step 3).
2. Checking For EGR Codes. If EGR service codes 31, 32, 33 or 34 are displayed, reconnect ISC solenoid and go to ENGINE RUNNING SELF-TEST table and perform appropriate CIRCUIT TEST. If these codes are not displayed, go to next step.
3. Checking Other Codes. If Codes 22, 41, 42, 91, or 92 are displayed, reconnect ISC solenoid, go to ENGINE RUNNING SELF-TEST table and perform appropriate CIRCUIT TEST. If these codes are not displayed, go to next step.
4. Measuring ISC Solenoid Resistance. Turn key off. Disconnect ISC solenoid. Set DVOM on 200-ohm scale, and measure resistance of ISC solenoid. If resistance is between 7 and 13 ohms, go to next step. If resistance is less than 7 ohms or more than 13 ohms, replace ISC solenoid and repeat QUICK TEST. (Scheme 99): ISC Solenoid Connector
5. Checking For Internal Short to ISC Solenoid Case. With key off and ISC solenoid disconnected, set DVOM on 200K-ohm scale. Measure resistance from either ISC terminal pin to ISC solenoid housing. If reading is greater than 10K ohms, go to next step. If reading is 10K ohms or less, replace ISC solenoid. Repeat QUICK TEST.
6. Checking VPWR Circuit. Leave ISC harness disconnected. With KOEO, set DVOM on 20-volt scale. Measure voltage between VPWR circuit at ISC harness connector and battery ground terminal. If reading is less than 10.5 volts, repair open in circuit and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
7. Checking ISC Circuit Continuity. Turn key off and wait 10 seconds. Leave ISC solenoid disconnected. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. With DVOM on 200-ohm scale, measure resistance between test pin No. 21 and ISC circuit at ISC harness connector. If reading is greater than 5 ohms, repair open circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
8. Checking For Circuit Short to Ground. Turn key off and wait 10 seconds. Leave ISC solenoid disconnected. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 21 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short to ground and repeat QUICK TEST. If all readings are 10K ohms or more, go to next step.
9. Checking For Short to Power. Turn key off and wait 10 seconds. Leave breakout box installed. Leave ECA and ISC solenoid disconnected. Set DVOM on 200K-ohm scale. Measure resistance by connecting DVOM negative lead to test pin No. 21 and positive lead to test pin No. 37. If reading is greater than 10K ohms, go to next step. If reading is 10K ohms or less, repair short to power and repeat QUICK TEST. If code or symptom is still present, replace ECA.
10. Checking ISC Signal From ECA. With key off, connect ECA and ISC. Leave breakout box installed and set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40. Start engine and observe DVOM while slowly increasing and decreasing engine RPM. If DVOM reading varies, go to next step. If DVOM reading does not vary, replace ECA and repeat QUICK TEST.
11. Checking Base/Curb Idle. Verify base/curb idle speed. If base/curb idle speed is within specifications, remove ISC solenoid and inspect for contamination, service as necessary. Rerun QUICK TEST, if code or symptom is still present, replace ISC solenoid. If curb idle speed is incorrect, reset idle speed to specification. Rerun QUICK TEST. If unable to set idle to specification, go to next step.
12. Check Faults Which Affect Idle Speed. Check the following mechanical items for faults: Throttle linkage and/or cruise control linkage for sticking or binding. Throttle body for contamination. Vacuum hoses (check emission decal). If all of the above items are okay, remove ISC solenoid and inspect for contamination. Service as necessary and rerun QUICK TEST. If code or symptom is still present, replace ISC. If any of the above items are faulty, service as necessary and rerun QUICK TEST.
13. Code 13: Verify Idle Speed is Within Specification. On 2.3L Turbo MPFI engines, Code 13 indicates that during KOER SELF-TEST, engine RPM did not reach lower limit in Self-Test. On all other engines, Code 13 indicates engine could not be controlled within lower RPM range. Possible causes for this fault are as follows: Incorrect idle setting. Vacuum leaks. Sticking or binding throttle linkage. Throttle plates open. Incorrect ignition timing (TFI ignition only). Throttle body or ISC solenoid contamination. ISC circuit shorted to ground. Faulty ISC solenoid. If all of the above components are okay, and idle is set to specification, remove ISC solenoid and inspect for contamination. Service as necessary and rerun QUICK TEST. If code or symptom is still present, replace ISC solenoid. If idle speed is not set to specification, reset and rerun QUICK TEST. If idle speed cannot be reset to specification, go to step 6) of this test.
14. Check For Conditions Affecting Idle Speed. Check the following mechanical components for faults: Engine vacuum hoses (refer to emission decal). Throttle linkage and/or cruise control linkage for sticking or binding. Check throttle plates are fully closed. Check for vacuum leaks in induction system. Check throttle body for contamination. Ensure base ignition timing is to specification on emission decal (TFI vehicles only). If all above checks are okay, go to next step. If a fault has been found, service as necessary and rerun QUICK-TEST.
15. Checking For Internal Short to ISC Solenoid Case. With key off and ISC solenoid disconnected, set DVOM on 200K-ohm scale. Measure resistance from either ISC terminal pin to ISC solenoid housing. If reading is greater than 10K ohms, go to next step. If reading is 10K ohms or less, replace ISC solenoid. Repeat QUICK TEST.
16. Checking For Circuit Short to Ground. Turn key off and wait 10 seconds. Leave ISC solenoid disconnected. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 21 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short to ground and repeat QUICK TEST. If all readings are 10K ohms or more, go to next step.
17. Checking ISC Signal From ECA. With key off, connect ECA and ISC. Leave breakout box installed and set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40. Start engine and observe DVOM while slowly increasing and decreasing engine RPM. If DVOM voltage reading varies, remove ISC solenoid and inspect for contamination, service as necessary. Rerun QUICK TEST, if code or symptom is still present, replace ISC solenoid. If DVOM voltage does not vary, replace ECA and rerun QUICK TEST.
18. Code 47: Check For Low Flow of Unmetered Air. Code 47 indicates that measured airflow at base idle was lower than ECA specification. Possible causes for this fault are: air/vacuum leaks in fuel charging system or faulty or leaking purge solenoid and/or injector "O" rings. Service any faults as necessary and rerun QUICK TEST. If no faults are present, EEC-IV system is okay, service other codes as necessary.
19. Code 48: Check For High Flow of Unmetered Air. Code 48 indicates that measured airflow at base idle was higher than ECA specification. Possible causes for this fault are: air/vacuum leaks in fuel charging system or loss of ignition or fuel. Check for and repair holes, cracks, and/or bad connections at air cleaner outlet tube (between vane airflow meter and fuel charging assembly). Check for loss of ignition or injection on one or more cylinders. If any faults are found, service as necessary. Rerun QUICK TEST. If no faults are found, EEC-IV system is okay for metered air.
20. Code 16: High ISC RPM. Code 16 indicates that with ISC off, engine RPM was above Self-Test specification limit. Possible causes for this fault are: incorrect idle adjustment, faulty purge solenoid, air/vacuum leaks. If Code 48 is also present, reset throttle plate. Refer to Vehicle Emission Control Decal for curb idle set procedure. Rerun QUICK TEST. If Code 48 is still present, go to step 19) of this test. If Code 48 is not present, go to step 13) of this test.
21. Code 19: ISC RPM Low. Code 19 indicates that with ISC off, engine RPM dropped below Self-Test limit (about 600 RPM). Possible causes for this fault are: engine below normal operating temperature, throttle body/air inlet contamination or incorrect idle speed adjustment. Turn key off and wait 10 seconds. Deactivate SELF-TEST. Start and run engine at 2000 RPM for 2 minutes or until top radiator hose is hot and pressurized. Turn key off and wait 10 seconds. Rerun KOER SELF-TEST. If engine stumbles and/or Code 19 is still displayed, inspect throttle body and air inlet for contamination, service as necessary and adjust curb idle. Rerun QUICK TEST. If Code 19 has been cleared, service other codes as necessary.
22. Code 17: ISC RPM Low. Code 17 indicates that with the ISC off, engine RPM was below Self-Test limit. Possible causes for this fault are: excessive engine accessory load, engine temperature below normal operating temperature, throttle body/air inlet contamination or incorrect idle adjustment. Check and correct excessive engine load conditions, cooling fans, lights, etc. Run engine at 2000 RPM for 2 minutes. Turn key off and wait 10 seconds. Rerun KOER SELF-TEST. If Code 17 is displayed, inspect throttle body and air inlet for contamination and clean as necessary. If okay, adjust base/curb idle speed and repeat QUICK TEST. If Code 17 is not displayed, service other codes as necessary.

1.9L MPFI Shift Indicator Light (SIL) Circuits. Scheme 100

All Other Shift Indicator Light (SIL) Circuits. Scheme 101

1. Checking SIL Operation. Inspect SIL while driving vehicle. SIL should turn on when optimum shift RPM is reached in each gear. Light should be off in highest gear. If SIL light is always on, check for a short in SIL circuit. If light is always off, check for an open in SIL circuit. If light is always on, go to step 6). If light is always off, go to next step.
2. Check SIL Circuit Fuse. Turn key off and wait 10 seconds. Remove and inspect SIL fuse (No. 18). If fuse is okay, reconnect and go to next step. If fuse is blown, repair short to ground between fuse and SIL bulb. Replace fuse and check SIL operation.
3. Check SIL Bulb. With key off, remove and inspect SIL bulb. If bulb is okay, go to next step. If bulb has failed, replace and check SIL operation.
4. Check Continuity of SIL Dimmer Relay. With key off, disconnect SIL dimmer relay. Set DVOM on 200-ohm scale. Measure resistance between pins No. 3 and 5 on SIL dimmer relay. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, replace SIL dimmer relay and check operation.
5. Check SIL Dimmer Relay Function. With key off, disconnect SIL dimmer relay. Apply 12 volts across pins No. 1 and 2 of SIL dimmer relay. With DVOM on 200-ohm scale, measure resistance between pins No. 3 and 5 on SIL dimmer relay. If resistance is between 40 and 55 ohms, go to next step. If resistance is not 40-55 ohms, replace SIL dimmer relay and retest operation.
6. Check Voltage at SIL Dimmer Relay. With KOEO, disconnect SIL dimmer relay. Set DVOM on 20-volt scale. Measure voltage between test pin No. 5 of the SIL dimmer relay harness connector and the battery negative post. If voltage is greater than 5 volts, reconnect relay and go to next step. If voltage is less than 5 volts repair circuit between top gear switch and SIL dimmer relay. Recheck SIL operation.
7. Check Voltage at Top Gear Switch. With KOEO, disconnect top gear switch. Set DVOM on 20-volt scale. Measure voltage between the SIL dimmer relay side of the top gear switch harness connector and battery negative post. If voltage is greater than 5 volts, go to next step. If voltage is less than 5 volts, repair circuit between high gear switch and dimmer relay. Check SIL operation.
8. Checking Operation of Top Gear Switch. Turn key off and wait 10 seconds. Disconnect high gear switch. Set DVOM on 200-ohm scale. Measure resistance of top gear switch while shifting transmission from top gear to the next lower gear. If switch opens and closes, go to next step. If circuit does not open and close, replace switch and check operation.
9. Checking Continuity of SIL Circuit. Turn key off, and disconnect high gear switch. Install breakout box and leave ECA disconnected. Set DVOM on 200-ohm scale, and measure resistance between test pin No. 53 and the ECA side of the high gear switch. If resistance is less than 5 ohms, reconnect high gear switch, shift transmission into high gear and go to next step. If resistance is more than 5 ohms, repair circuit between high gear switch and ECA.
10. Checking SIL Circuit For Short to Ground. Turn key off, and place transmission in highest gear. Set DVOM on 200-ohm scale, and install breakout box, leaving ECA disconnected. Measure resistance between test pin No. 53 and test pin No. 60. If resistance is less than 100K ohms, repair short between high gear switch and ECA. If resistance is greater than 10K ohms, respace ECA and rerun QUICK TEST.

2.3L MPFI Truck Engine WOT A/C Cut-Out Circuits. Scheme 102

2.3L HSC MPFI Engine WOT A/C Cut-Out Circuits. Scheme 103

2.3L OHC MPFI Engine WOT A/C Cut-Out Circuits. Scheme 104

2.3L Turbo MPFI WOT A/C Cut-Out Circuits. Scheme 105

Scheme 106

Scheme 107

1. No A/C: Check For Voltage at A/C Clutch. Check all A/C related fuses in fuse panel before proceeding with this test. Use only DVOM, not diagnostic tester, for this step. Disconnect A/C clutch harness connector. Turn A/C switch to "A/C" position. Set DVOM on 20 volt scale. Start engine and wait 10 seconds. Measure voltage between the power side of the A/C clutch harness connector and negative battery terminal. If voltage is greater than 10.5 volts, EEC-IV system is okay, diagnose A/C clutch system. If voltage is less than 10.5 volts, go to next step for 2.3L Turbo MPFI. Go to step 5) for all other models.
2. Check Voltage at A/C De-Icing Switch. With key off, disconnect A/C clutch harness. Disconnect A/C de-icing switch. Turn A/C switch to ON position. Set DVOM to 20-volt scale. Start engine and wait 10 seconds. Measure voltage between both Power-from-WAC relay circuits at the A/C de-icing switch harness connector to chassis ground. If both voltages are greater than 10.5 volts, turn key off and go to step 4). If both voltages are not greater than 10.5 volts, reconnect A/C clutch harness and go to next step. (Scheme 106): A/C De-Icing Switch
3. Check Continuity From WAC Relay to De-Icing Switch. Turn key off, and disconnect A/C de-icing switch. Set DVOM on 200-ohm scale. Measure resistance between Power-to-Clutch circuit on the WAC relay harness connector and both Power-from-WAC relay circuits on the A/C de-icing switch harness connector. If both resistances are less than 5 ohms, go to step 6). If both resistances are not less than 5 ohms, repair open circuit, reconnect components and retest system. (Scheme 107): WAC Relay Harness Connector
4. Check Continuity From A/C De-Icing Switch to A/C Clutch. With key off, disconnect A/C clutch harness. Set DVOM on 200-ohm scale. Measure resistance between power side of A/C clutch harness connector and Power-to-Clutch terminal at A/C de-icing switch. If resistance is less than 5 ohms, check ground circuit to A/C de-icing switch. If circuit is okay, problem is not EEC-IV related. Service or replace A/C de-icing switch. If resistance is greater than 5 ohms, check operation of 3-way pressure switch. If 3-way pressure switch is okay, repair open circuit and retest system.
5. Checking Continuity of Power-to-Clutch Circuit. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect A/C clutch harness and harness from WAC relay or A/C fan controller. Measure resistance between power side of A/C clutch harness connector and Power-to-Clutch terminal pin at WAC relay or A/C fan controller. If resistance is less than 5 ohms, reconnect A/C clutch and go to next step. If resistance is more than 5 ohms, service open circuit and re-test system. System application is as follows: WAC Relay 2.3L Turbo MPFI 2.3L MPFI Truck A/C Fan Controller 2.3L HSC MPFI 2.3L OHC MPFI
6. Checking Power on A/C Demand Circuit. With KOEO and WAC relay or A/C fan controller disconnected, turn on A/C switch. Set DVOM to 20-volt scale. Measure voltage between A/C demand input terminal pin at WAC relay or A/C fan controller harness connector and ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, check switch operation, repair open circuit and retest system.
7. Checking WAC Circuit For Short to Ground. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and WAC relay or A/C fan controller. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between WAC circuit at WAC relay or A/C fan controller and chassis ground. If resistance is greater than 10K ohms, go to next step for A/C fan controller systems or step 10) for WAC relay systems. If resistance is less than 10K ohms, repair short and retest system.
8. Checking A/C Fan Controller Ground Circuit. With key off and A/C fan controller disconnected, set DVOM on 200-ohm scale. Disconnect ECA. Measure resistance between ground circuit at A/C fan controller harness connector and chassis ground. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open circuit and retest system.
9. Checking For Voltage to A/C Fan Controller. With key on, ECA and A/C fan controller disconnected, set DVOM on 20-volt scale. Measure voltage between ignition switch RUN circuit at the A/C fan controller harness connector and chassis ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open circuit, reconnect ECA and A/C controller and re-test system.
10. Checking WAC Relay or A/C Fan Controller. Turn key off and wait 10 seconds. Leave ECA disconnected and reconnect WAC relay or fan controller. Set DVOM on 20-volt scale. With KOEO and A/C on, measure voltage between power side of A/C clutch harness connector and battery negative terminal. If voltage is greater than 10.5 volts, replace ECA, reconnect A/C clutch and retest system. If voltage is less than 10.5 volts, replace WAC relay or fan controller. Retest system.
11. Checking A/C Output at WOT. Enter OUTPUT STATE CHECK, see OUTPUT STATE CHECK under DIAGNOSTIC AIDS. Use a VOM or DVOM meter for this test. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative (-) lead to STO at Self-Test connector and positive lead to positive (+) battery terminal. Jumper STI to SIG RTN at Self-Test connector. Perform KOEO SELF-TEST until completion of Continuous Memory Code sequence. Meter will indicate less than one volt when test is complete. Depress and release throttle. If voltage increases to 10.5 volts or more, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase to 10.5 volts, leave test equipment connected and go to test D16, step 2).
12. System Identification. If vehicle is equipped with WAC relay, go to step 17). If vehicle is equipped with A/C fan controller, go to step 22). WAC Relay 2.3L Turbo MPFI 2.3L MPFI Truck A/C Fan Controller 2.3L HSC MPFI 2.3L OHC MPFI
13. Checking VPWR to Relay. With vehicle in OUTPUT STATE CHECK, disconnect harness from WAC relay and set DVOM on 20-volt scale. Measure voltage between VPWR circuit (START/RUN circuit for 2.3L Turbo MPFI) at the WAC relay harness connector and chassis ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open circuit, remove test equipment, and retest system.
14. Checking WAC System For Cycling. With vehicle in OUTPUT STATE CHECK, disconnect harness from WAC relay and set DVOM on 20-volt scale. Connect positive test lead to VPWR circuit (START/RUN circuit for 2.3L Turbo MPFI) and negative test lead to WAC circuit at WAC relay harness connector. Check DVOM while depressing and releasing throttle several times, to cycle system. If voltage cycles from high to low, replace WAC relay and retest system. If voltage does not cycle, remove test leads and go to next step.
15. Checking Continuity of WAC Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and WAC relay disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 54 and WAC circuit at relay connector. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
16. Checking For Short to Power. Turn key off and wait 10 seconds. Leave breakout box installed, ECA and WAC relay disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 54 and test pins No. 37 and 57. If any reading is less than 10K ohms, repair short circuit and repeat QUICK TEST. If all readings are 10K ohms or more, replace ECA and retest system.
17. Check WAC Cycling. With vehicle in OUTPUT STATE CHECK, disconnect A/C fan controller and set DVOM on 20-volt scale. Connect DVOM positive test lead to ignition run circuit and negative test lead to WAC circuit at A/C fan controller harness connector. Check DVOM while depressing and releasing throttle several times, to cycle system. If voltage cycles from high to low, replace A/C fan controller and re-test system. If voltage does not cycle, remove jumper and go to next step.
18. Checking Continuity of WAC Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and fan controller disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 54 and WAC circuit at WAC relay harness connector. If reading is 5 ohms or more, repair open in harness and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
19. Checking For Short to Power. Turn key off and wait 10 seconds. Install breakout box, ECA and A/C fan controller disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 54 and test pins No. 37 and 57 at the breakout box. If all readings are greater than 10K ohms, replace ECA, reconnect A/C fan controller and retest system. If any reading is 10K ohms or less, repair short to power and repeat QUICK TEST. If symptom is still present, replace ECA.
20. Cycle A/C Demand Switch. Turn key off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. With KOEO, connect DVOM positive test lead to test pin No. 43 (No. 24 on 2.3L OHC MPFI) and negative test lead to test pin No. 40. If voltage goes high and low as switch is cycled, replace ECA and retest system. If voltage does not cycle, go to next step.
21. Checking Continuity of A/C Demand (ACD) Circuit. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 43 (No. 24 on 2.3L OHC MPFI) at the breakout box and A/C demand switch. If resistance is greater than 5 ohms, repair open in A/C demand circuit and rerun QUICK TEST. If resistance is less than 5 ohms, EEC-IV system is okay.
22. Checking A/C Demand (ACD) Circuit For Short to Power. Disconnect WAC relay or A/C fan controller. Disconnect ECA and install breakout box. With A/C demand switch "OFF", set DVOM on 20-volt scale. Turn key on. Measure voltage between test pin No. 24 (No. 43 on 2.3L Turbo MPFI) at breakout box and chassis ground. If voltage is less than one volt EEC-IV system is okay. If voltage is more than one volt, check operation of A/C demand switch, repair short circuit and retest system.

D8 - OCTANE ADJUST

Note. Enter this test when directed here by Diagnosis By Symptom Test in QUICK TEST procedure.

Octane Adjust Circuit. Scheme 108

Note. This test is intended to diagnose the following

1. Harness circuits, VPWR and OCTANE ADJUST
2. Octane Adjust Shorting Bar connector

OCTANE ADJUST SHORTING BAR LOCATIONS

The purpose of the Octane Adjust Shorting Bar is to provide optimum spark advance for the fuel being used. If the vehicle engine detonates (spark knock), REMOVE the Octane Shorting Bar. This retards spark advance about 3 to 4 degrees. If the vehicle continues to detonate, use fuel with a higher octane rating.

D9 - SUPERCHARGER BY-PASS SOLENOID (SBS)

Note. Perform this test when Service Code 82 is displayed or when directed here by other test procedures.

SBS Circuit. Scheme 109

1. Code 82: Check Solenoid Resistance. Code 82 indicates that voltage output for the SBS did not change when activated by the ECA during KOEO SELF-TEST. Possible causes for this fault are: open or shorted SBS circuit, open or grounded ECA driver or disconnected or open solenoid. With key off, set DVOM on 20-volt scale. Disconnect SBS solenoid and measure solenoid resistance. If resistance is between 50 and 100 ohms, go to next step. If resistance is not 50-100 ohms, replace SBS and rerun QUICK TEST.
2. Check Voltage On VPWR Circuit. With KOEO, set DVOM on 20 volt scale. Measure voltage between SBS VPWR circuit and battery ground. If voltage is greater than 10.5 volts, go to next step. If voltage was less than 10.5 volts, repair open circuit and rerun QUICK TEST.
3. Check Continuity of SBS Circuit. Turn key off, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 38 at the breakout box and SBS circuit at the vehicle harness. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit, reconnect ECA and rerun QUICK TEST.
4. Check For Short to Ground. Set DVOM on 200K-ohm scale. Install breakout box, leave ECA disconnected. Disconnect SBS. Measure resistance between test pin No. 38 and test pins No. 40, 46 and 60, at the breakout box. If resistance is greater than 10K ohms, go to next step. If resistance is less than 10K ohms, repair short to ground and rerun QUICK TEST.
5. Check For Shorts to Power. With key off and DVOM on 200K ohm scale, Install breakout box and leave ECA and SBS disconnected. Measure resistance between test pin No. 38 and test pin No. 1 at the breakout box. If resistance is greater than 10K ohms, remove breakout box and reconnect SBS, replace ECA and rerun QUICK TEST. If resistance is less than 10K ohms, repair short to power, rerun QUICK TEST. If Code 82 is still present, replace ECA. NOTE: You should have been directed to test step 6) by the Diagnosis By Symptom chart.
6. Check Supercharger By-pass Valve. With key off, disconnect vacuum line from supercharger by-pass valve. Apply 16 in. Hg to valve. If valve holds vacuum, go to next step. If valve does not hold vacuum, replace it and retest.
7. Check By-pass System. With key off, apply vacuum to valve and visually observe valve and linkage. If valve operates linkage correctly, go to next step. If linkage does not operate correctly, repair as necessary and retest.
8. Check Vacuum Supply to By-pass Valve. With key off, check vacuum hose between supercharger valve and SBS for damage or blockage. If hose and connections are okay, go to next step. If hose is faulty, replace as necessary and rerun QUICK TEST.
9. Check Vacuum Supply. Disconnect source vacuum hose from SBS. Start engine and check vacuum. If vacuum is present at hose replace SBS and rerun QUICK TEST. If vacuum is not present, service or repair vacuum source blockage and rerun QUICK TEST.

D10 - DYNAMIC RESPONSE TEST

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: person testing EEC system did not perform brief Wide Open Throttle (WOT) after Dynamic Response code, mechanical engine problems, or engine did not go over 2000 RPM. This test is intended to diagnose the following

1. Throttle movement (Minimum 3/4 throttle).
2. Vane Airflow Meter (VAF) open at least 50%.
3. RPM increase greater than 2000 RPM.

Note. If throttle is snapped open briefly it may not pass the WOT test. Ensure that the throttle is depressed fully to WOT and that engine exceeds 2000 RPM.

Code 77 Displayed: System Failed to Recognize WOT Test. Rerun KOER SELF TEST as follows

1. Start engine.
2. Activate KOER SELF-TEST.
3. Observe ID code 2 (0 with STAR tester).
4. Observe Dynamic Response Code 1 (0 with STAR tester).
5. Perform brief WOT.
6. Testing complete, service code output begins.

If Code 77 is still displayed, replace ECA and rerun QUICK TEST. If Code 77 is no longer present, vehicle has passed Dynamic Response test, service other codes as necessary.

D11 - "CHECK ENGINE" LIGHT/MESSAGE (MALFUNCTION INDICATOR)

Note. To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuses, bulb, or socket. This circuit test checks STO-MIL circuit and ECA. You should perform this test when Codes 70, 71 or 72 is displayed, or when directed here by other test procedure.

CHECK ENGINE Light (Malfunction Indicator) Circuit (1 of 2). Scheme 110

CHECK ENGINE Light (Malfunction Indicator) Circuit (2 of 2). Scheme 111

Note. All service codes, except a Code 11 (pass), must be cleared before continuing.

1. "CHECK ENGINE" Light Always On: Checking Short to Ground. If vehicle will not start, go to «A1 - NO START»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) , step 1). Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Connect DVOM between test pins No. 17 and No. 40 at the breakout box. If resistance is greater than 10K ohms, replace ECA. If reading is less than 10K ohms, repair short between test pin No. 17 and SELF-TEST connector or "CHECK ENGINE" light.
2. "CHECK ENGINE" Light Never On: Check Continuity of STO/MIL Circuit. If vehicle will not start, go to «A1 - NO START»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) , step 1). Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 17 and "CHECK ENGINE" light. If resistance is less than 5 ohms, go to next step. If not, repair open circuit in wiring harness and rerun QUICK TEST.
3. Checking For Power to "CHECK ENGINE" Light Bulb. If power exists at bulb, replace bulb or socket and go to next step. If no power exists at socket, check fuse and input circuit, and then go to next step.
4. Confirming Circuit Repair. Remove breakout box and reconnect ECA to harness. Turn key to "RUN" position. See if "CHECK ENGINE" light is on. If light is on, malfunction indicator system is okay. If light does not come on, replace ECA.
5. "CHECK ENGINE" Intermittent, Check Short From STO to Ground. If vehicle does not start, go to «A1 - NO START»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) , step 1). Service all Continuous Memory Codes before proceeding. If no codes are outputted, proceed with this test. Enter KOEO CONTINUOUS MONITOR MODE ("WIGGLE TEST"). Observe DVOM for indication of fault while performing "Wiggle" test on the harness in the following areas. From Self-Test connector to dash panel. Dash panel to ECA. Dash panel to "CHECK ENGINE" light. If a fault is indicated, repair as necessary and rerun QUICK TEST. If a fault is not indicated, fault cannot be duplicated at this time.
6. "CHECK ENGINE" Light Flashes With Erratic Idle: Check STI Short to Ground. Vehicle symptoms indicate STI is grounded and ECA is performing Self-Test without tester installed. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Set DVOM on 200K-ohm scale. Measure resistance between STI connector and engine block ground. If resistance is less than 10K ohms, repair short circuit. Reconnect ECA and retest. If reconnect ECA and test for other rough idle symptoms.
7. "CHECK ENGINE" Message Displayed. If vehicle will not start, go to «A1 - NO START»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) . Perform KOEO SELF-TEST, if the result is a pass code (11-10-11), repair fault in electronic message center Data Communications Link (DCL). If Pass Code is not displayed, service codes as described in Self-Test procedures.
8. Continuous Memory Code 70, 71 and 72: "CHECK ENGINE" Light On. Codes 70, 71 and 72 indicate a circuit failure has occurred on the Data Communications Link (DCL). These codes can occur alone or together. "CHECK ENGINE" message will be on. Code 70 indicates ECA is unable to transmit data. Code 71 indicates Cluster Control Assembly (CCA) is unable to transmit data. Code 72 indicates that Message Center Control Assembly (MCCA) is unable to transmit data. Perform KOEO SELF-TEST, if the result is a Pass Code (11-10-11), repair fault in electronic message center Data Communications Link (DCL). If pass code is not displayed, service codes as described in Self-Test procedures.

D12 - IGNITION DIAGNOSTIC MONITOR (IDM)

Note. This test procedures has been revised based on updated procedures in Ford Technical Service Bulletin, 89-18A-10.

IDM Circuit. Scheme 112

Note. Perform this test when Service Code 14, 18, 19, 28, 45, 46, 48 or 88 is displayed during QUICK TESTS or when directed here by other test procedures.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault

1. TFI or DIS ignition module.
2. Ignition coil or DIS coil packs.
3. Spark plugs and/or high tension cables.
4. Distributor and PIP sensor.
5. Secondary ignition component arcing.

This test is intended to diagnose the following circuits and components.

1. Harness circuits: IGNITION GROUND, SPOUT, PIP, IDM & DPI
2. ECA assembly

There are 3 types of ignition system connections used with EEC-IV. They are configured as follows

Distributorless Ignition System (DIS) - Two 6-pin connectors located at top and bottom of DIS module. Pins No. 1-6 are located on the top of the module. Pins No. 7-12 are located in the connector on the bottom of the module.

Closed Bowl Distributor (CBD) - TFI module is located on the cowl, away from the distributor. The previous mounting window in the bowl of the distributor is closed. Two connectors are used, one connecting the harness to the vehicle Hall sensor, located in the distributor, and another connecting the harness to the TFI module.

TFI Module Distributor - This is the most common system. The TFI module is mounted in the distributor and a single module connector is used.

IGNITION SYSTEM APPLICATIONS

1. Code 14: Erratic Ignition. Code 14 indicates two successive erratic Profile Ignition Pickup (PIP) pulses occurred, resulting in a possible engine miss or stall. Possible causes for this fault are: loose wires or connectors, arcing secondary ignition components or on-board transmitter equipment (2-way radio). If any of the above are present, service as necessary, clear code and rerun QUICK TEST. If the items listed are not present, go to step 3).
2. Check For Other Codes. If Codes 45, 46 or 48 are present, go to step 12). If Codes 45, 46 or 48 are not present, go to next step.
3. Continuous Memory Codes 14, 18, 28 or 48: Check IDM Circuit Continuity. Code 18 indicates a loss of IDM input signal. Possible causes: Open harness circuit Shorted harness Faulty TFI or DIS module Faulty ECA Code 28 indicates IDM input signal always low. Possible causes: Open or shorted harness Faulty CID sensor VBAT (battery voltage) low at DIS Faulty DIS module Faulty ECA Code 48 indicates IDM input signal always high. Possible causes: Open signal in harness VBAT open at secondary coil VBAT low at secondary coil NOTE: On TFI vehicles the IDM circuit has a 22K-ohm resistor between test pin No. 4 and the ignition coil negative terminal. Turn key off an wait 10 seconds. Disconnect E-core ignition coil on TFI vehicles and DIS module connector (pins No. 7-12) on DIS equipped vehicles. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leave ECA connected and set DVOM on 200K-ohm scale. On TFI equipped vehicles, measure resistance between test pin No. 4 at the breakout box and negative terminal of ignition coil harness connector. On DIS equipped vehicles, measure resistance between test pin No. 4 at the breakout box and DIS module harness connector pin No. 12. If resistance is between 20K and 24K ohms, go to next step. If resistance is not to specification, repair open circuit, clear codes, retest and reconnect E-core coil.
4. Checking IDM Circuit For Short to Ground. Turn key off and wait 10 seconds. Disconnect E-core ignition coil on TFI vehicles and DIS module connector (pins No. 7-12) on DIS equipped vehicles. Install breakout box and ECA disconnected. With DVOM on 200K-ohm scale, measure resistance between test pin No. 4 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short to ground in IDM circuit, reconnect all components and rerun QUICK TEST. If all readings are 10K ohms or more, reconnect components and go to next step.
5. Checking ECA For Short to Ground. Turn key off and wait 10 seconds. Disconnect E-core ignition coil on TFI vehicles and DIS module connector (pins No. 7-12) on DIS equipped vehicles. Install breakout box and connect ECA. With DVOM on 200K-ohm scale, measure resistance between test pin No. 4 and test pins No. 40, 46, and 60. If any reading is less than 10K ohms, replace ECA, reconnect all components and rerun QUICK TEST. If all readings are 10K ohms or more, reconnect components and go to next step.
6. Checking Ignition Module. Turn key off and wait 10 seconds. Deactivate SELF-TEST. Using CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while lightly tapping on TFI or DIS module to simulate road shock. Wiggle TFI or DIS harness connectors. On Closed Bowl Distributor (CBD) models, wiggle TFI and distributor hall connectors. If fault is indicated, disconnect and inspect TFI harness connectors and terminals for damage. If connector and terminals are okay, check TFI ignition system, if ignition is okay, replace ECA. If no fault is indicated, go to next step.
7. Checking EEC-IV Harness. While in CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while wiggling, shaking, or bending small sections of harness while working from TFI or DIS connector toward firewall. Repeat process from firewall to ECA. On CBD systems also test distributor Hall connector. Perform this test to check for faults in the following circuits: CIRCUIT FAULT CHECKS Condition Test Pin # PIP Open/Shorted to Ground Check circuit at test pin No. 56. SPOUT Shorted to Ground Check circuit at test pin No. 36. Ignition Ground Open Check circuit at test pin No. 16. IDM Open to Ground Check circuit at test pin No. 4. IDM Shorted to Power Check circuit at test pin No. 4. Perform CONTINUOUS MONITOR (WIGGLE) TEST on these circuits one at a time in order to isolate fault. If fault is indicated, isolate fault and repair harness. Repeat QUICK TEST. If no fault is indicated, go to next step.
8. Checking ECA and Harness Connectors. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary, clear codes and repeat QUICK TEST. If connector is okay, perform the following procedure based on the Continuous Memory Code displayed: Code 14: Unable to duplicate erratic ignition fault in EEC system. Remove breakout box, reconnect all components. Diagnosis DIS ignition system. Code 18: Replace ECA, remove breakout box and reconnect all components. Start and run engine for about one minute and rerun QUICK TEST. Codes 28 and 48: Remove breakout box and reconnect all components. Diagnose ignition system. If ignition system is okay, replace ECA.
9. Continuous Memory Code 19: Check Camshaft Sensor Output. Code 19 indicates one of the 2 Cylinder Identification (CID) sensor output signals has failed. One of the outputs is a signal sent to the DIS and the second output is the signal to the ECA. Both outputs have a 50% duty cycle of 0.4 volt to battery voltage (VBAT). Possible causes for this fault are; open or short in CID-to-ECA circuit. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary. Install breakout box and connect ECA. With KOER, and DVOM set on AC scale, measure voltage between test pin No. 24 and GROUND. If voltage varies, replace ECA, remove breakout box, reconnect all components and rerun QUICK TEST. If voltage does not vary, go to next step.
10. Check CID Harness For Continuity. With key off and breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 24 at the breakout box and Pin 2 (CID)at the DIS module connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit, remove breakout box, reconnect all components and rerun QUICK TEST.
11. Check CID Circuit For Shorts. Turn key off, Install breakout box, disconnect ECA. Disconnect DIS module. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 24 and test pins No. 16, 37 and 40 at the breakout box. If all resistances are not greater than 10K ohms, repair CID circuit to GROUND or POWER. Remove breakout box, reconnect all components and rerun QUICK TEST. If all resistances are greater than 10K ohms, remove breakout box, reconnect all components and diagnose TFI or DIS system.
12. Continuous Memory Codes 45, 46 or 48: Check Continuity of Coil Circuits From DIS to Coil Pack. Codes 45, 46 and 48 indicate a fault has been detected by the ECA in one of the 3 coils contained in the ignition pack. Possible causes for this fault are: an open in coil circuit from DIS module to coil pack or short to coil circuit GROUND or POWER in DIS module. NOTE: Codes 45, 46 and 48 refer to faults related to coils No. 3, 1, or 2 respectively. Coil No. 1 provides voltage to cylinders No. 3 and 4 spark plugs. Coil No. 2 provides voltage to cylinders No. 2 and 6 spark plugs. Coil No. 3 provides voltage to cylinders No. 1 and 5 spark plugs. The IDM input contains a pulse signal for each operating coil. If that coil fails, the corresponding pulse will be missing from the IDM input pulse signal. Turn key off and wait 10 seconds. Disconnect DIS module and set DVOM on 200-ohm scale. Measure resistance as described for appropriate service code: Code 45: Measure resistance between pin No. 8 at the DIS module and coil pin No. 3 at coil pack. Code 46: Measure resistance between pin No. 11 at the DIS module and coil pin No. 1 at coil pack. Code 48: Measure resistance between pin No. 9 at the DIS module and coil pin No. 2 at coil pack. If all resistances are less than 5 ohms, go to next step. If resistances are greater than 5 ohms, repair open circuit and reconnect all components. Rerun QUICK TEST.
13. Checking Coil Pack For Shorts to Ground and Power. With key off, disconnect coil pack and DIS module connector (pins No. 7-12). Set DVOM on 200K-ohm scale. Measure resistance between pin No. 7 and pins No. 8, 9 and 11 at the DIS module connector. Measure resistance between pin No. 1 and pins No. 8, 9 and 11 at the DIS module connector. If all resistances are greater than 10K ohms, diagnose DIS ignition system. If all resistances are not greater than 10K ohms, repair short circuit, reconnect all components, and rerun QUICK TEST.
14. Continuous Memory Code 88: Check Continuity of DPI Circuit. Code 88 indicates an open in the Dual Plug Inhibit (DPI) circuit or an open or short to ground in coil No. 4. Possible causes for this fault are: open or short circuit in harness, Faulty ECA or DIS module or faulty coil No. 4. Turn key off and wait 10 seconds. Disconnect DIS connector (pins No. 7-12). Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary. Install breakout box and leave ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between pin No. 6 at the DIS vehicle harness connector and test pin No. 32 at the breakout box. If resistance is less than 5 ohms, remove breakout box, reconnect all components. Diagnose DIS ignition system. If system is okay, replace ECA. If resistance is not less than 5 ohms, repair open circuit, remove breakout box, reconnect all components and rerun QUICK TEST.
15. Symptom: Hard Start, Check DPI Circuit For Short to Ground. Turn key off and wait 10 seconds. Disconnect DIS connector (pins No. 7-12). Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary. Install breakout box and leave ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 32 and test pins No. 40 and 60 at the breakout box. If resistance is greater than 100K ohms, go to next step. If resistance is less than 100K ohms, repair short circuit, remove breakout box, reconnect all components and rerun QUICK TEST.
16. Check ECA For Short to Ground. Turn key off and wait 10 seconds. Disconnect DIS connector (pins No. 7-12). Install breakout box and connect ECA. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 32 and test pins No. 40 and 60 at the breakout box. If resistance is greater than 500 ohms, remove breakout box, reconnect all components. Diagnose DIS ignition system. If resistance is less than 500 ohms, replace ECA, remove breakout box, reconnect all components and rerun QUICK TEST.

D13 - SPARK TIMING CHECK

Note. Perform this test when Service Code 18 or 49 is displayed during QUICK TESTS or when directed here by other test procedures.

Spark Timing Check Circuit (1 of 2). Scheme 113

Spark Timing Check Circuit (2 of 2). Scheme 114

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.), PIP sensor, and TFI ignition module. This test is intended to diagnose the SPOUT circuit in the harness, base timing and the ECA.

Scheme 115

1. KOER Code 18: Check Computed Spark Timing. On TFI vehicles, Code 18 indicates SPOUT circuit is open. Possible causes for this fault are: open harness circuit or faulty ECA or TFI module. On DIS vehicles, Code 18 indicates: SPOUT circuit is open or shorted to ground. Possible causes are; an open or shorted harness or faulty ECA or DIS module. Perform KOER SELF-TEST and verify that SELF-TEST is activated. Check and record timing while in KOER SELF-TEST. System locks timing for a period of 2 minutes after last service code is displayed. Computed timing during these 2 minutes is equal to base timing plus 20 degrees (+/-3 degrees). On 2.3L DIS Trucks, use exhaust side spark plug. If computed timing is correct, go to KOER SELF-TEST. If timing is not to specification, go to next step.
2. Checking Base Timing. Locate Spark Output (SPOUT) connector and open the connection. Start engine and check for 10 degrees BTDC base timing +/- 3 degrees. If base timing is correct, go to next step. If base timing is incorrect, on TFI equipped vehicles adjust base timing as necessary. After timing is reset, reconnect SPOUT and perform COMPUTED TIMING CHECK. On DIS equipped vehicles, base timing is not adjustable. diagnose DIS ignition system.
3. Checking For Power to ECA. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box. With KOEO, and DVOM set on 20-volt scale, measure voltage between test pins No. 37 and 40, and between test pins No. 57 and 60 at the breakout box. If either reading is less than 10.5 volts, go to «A2 - VEHICLE BATTERY»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a2-vehicle-battery), step 1). If both readings are 10.5 volts or more, go to next step.
4. Checking SPOUT Circuit For Continuity. Turn key off and wait 10 seconds. Install breakout box. Disconnect ECA and TFI or DIS module. With DVOM set on 200-ohm scale, measure resistance between test pin No. 36 (SPOUT) at breakout box SPOUT pin at TFI or DIS harness connector. If reading is greater than 5 ohms, repair open circuit. Connect SPOUT connector and check timing as described in step 1). If reading is 5 ohms or less, go to next step for DIS vehicles, or step 6) for all others. (Scheme 115): Module Connectors
5. Check SPOUT For Shorts. Turn key off and wait 10 seconds, Install breakout box and disconnect ECA. Set DVOM on 200K-ohm scale. Perform the following measurements: Shorts to Ground. Measure resistance between test pin No. 36 and test pins No. 16, 20, 40, 46 and 60. Shorts to Power. Measure resistance between test pin No. 36 and test pins No. 26, 37 and 57. Shorts to PIP Circuit. Measure resistance between test pin No. 36 and test pin No. 56. If all resistances are greater than 10K ohms, go to next step. If resistances are not greater than 10K ohms, service short circuit, remove breakout box, reconnect components and rerun QUICK TEST.
6. Checking ECA. Turn key off and wait 10 seconds. Install breakout box. Ensure ECA and TFI or DIS are connected. Set breakout box timing switch to "DIST" position. Set DVOM on 20-volt scale. Measure voltage between test pin No. 36 at the breakout box and battery negative terminal during KOER SELF-TEST. If voltage is between 4 and 10 volts, EEC system is okay, remove breakout box and diagnose TFI ignition system. If voltage is not between 4 and 10 volts, remove breakout box, replace ECA and rerun QUICK TEST.
7. Continuous Memory Code 49: Check Harness Continuity. Code 49 indicates SPOUT signal has defaulted to 10 degrees BTDC. The SPOUT signal has a variable duty cycle with a n amplitude of 4 volts to battery voltage (VBAT). If the SPOUT signal fails, the DIS module generates a fixed dwell and constant spark signal based on CID and PIP signals. This is the Failure Management Effects Mode (FMEM). Possible causes for this fault are: faulty DIS module or faulty SPOUT signal circuit from ECA to DIS module. Turn key off and wait 10 seconds. Install breakout box and leave ECA disconnected. Disconnect DIS module. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 36 at the breakout box and pin No. 5 at the DIS module connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, ensure SPOUT connector is okay. If okay, repair open circuit, reconnect all components and rerun QUICK TEST.
8. Check Spout Circuit For Short to Power or Ground. Turn key off and wait 10 seconds. Install breakout box. Disconnect ECA and DIS module. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 36 at the breakout box and test pins No. 16, 40 and battery positive. If all resistances are greater than 10K ohms, diagnose TFI or DIS ignition system. If resistances are less than 10K ohms, service SPOUT circuit for shorts. Reconnect all components and rerun QUICK TEST.

D14 - NO CODES/CODES NOT LISTED

Note. Perform this CIRCUIT TEST when directed by other test procedures.

No Codes/Codes Not Listed Circuits (1 of 3). Scheme 116

No Codes/Codes Not Listed Circuits (2 of 3). Scheme 117

No Codes/Codes Not Listed Circuits (3 of 3). Scheme 118

1. Checking For VREF. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, and connect ECA. Set DVOM on 20-volt scale. With KOEO, measure voltage between test pin No. 26 and SIGNAL RETURN at Self-Test connector. If reading is less than 4 volts or more than 6 volts, go to «A3 - REFERENCE VOLTAGE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__a3-reference-voltage) , step 1). If reading is between 4 and 6 volts, go to next step.
2. Checking SELF-TEST Input Continuity. Turn key off and wait 10 seconds. With breakout box installed and ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 48 at the breakout box and Self-Test Input (STI) at SELF-TEST connector pigtail. If reading is 5 ohms or more, repair open in circuit, remove breakout box and reconnect ECA. Rerun QUICK TEST. If reading is less than 5 ohms, go to next step.
3. Checking SELF-TEST Output Circuit Continuity. With breakout box installed and ECA disconnected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 17 at the breakout box and Self-Test Output (STO) at SELF-TEST connector. If reading is 5 ohms or more, repair open circuit, remove breakout box and reconnect ECA. Rerun QUICK TEST. If reading is less than 5 ohms, go to next step.
4. Checking EGO Sensor Ground Continuity. Turn key off. With breakout box installed and DVOM on 200-ohm scale, measure resistance between test pin No. 49 and EGO GROUND on engine block. If reading is 5 ohms or more, repair EGO sensor ground wire or open circuit. If reading is less than 5 ohms, go to next step.
5. Checking For STO Short to Ground. With breakout box installed and ECA disconnected, set DVOM on 200K-ohm scale. Measure resistance between STO at Self-Test connector and engine block ground. Rerun QUICK TEST. If reading is 10K ohms or less, repair STO or MIL/SIL circuit for short to ground and repeat QUICK TEST. If reading is greater than 5 ohms, go to next step.
6. Intermittent: Neutral Drive Switch (NDS), No Codes Displayed. Turn key off. Install breakout box, and connect ECA to breakout box. Set DVOM on 20-volt scale. Connect DVOM between test pin No. 30 and test pins No. 40 or 60 at the breakout box. Refer to the circuit diagram in «B13 - NEUTRAL DRIVE SWITCH (NDS) A/C INPUT»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__b13-neutral-drive-switch-nds) for this step. Perform KOER SELF-TEST. If reading is greater than one volt, repair intermittent open in NDS harness connector or switch. If okay, reconnect ECA and go to KOER SELF-TEST for appropriate service codes. If reading is less than one volt, go to next step.
7. Power Relay Always On. Leave key off and breakout box installed. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 37 or 57 and pins No. 40 or 60. Turn key on and then off. Wait 10 seconds. If reading does not change from 10.5 volts (or more) to zero volts, go to next step. If reading changes from 10.5 volts (or more) to zero volts, go to step 9) only if vehicle is equipped with Malfunction Indicator Light (MIL) or Shift Indicator Light (SIL). If vehicle is NOT equipped with either of these lights, replace ECA and repeat QUICK TEST. NOTE: Malfunction Indicator Light (MIL) is displayed as "CHECK ENGINE" light on instrument cluster.
8. VPWR Harness Short to Power. With key off, breakout box installed and EEC power relay or Integrated Relay Controller Module (IRCM) disconnected, set DVOM on 20-volt scale. Connect DVOM to test pin No. 37 or 57 and to test pin No. 40 or 46 at the breakout box. If voltage is greater than 10.5 volts, repair short to VPWR circuit and rerun QUICK TEST. If voltage is less than 10.5 volts, replace EEC-IV power relay or IRCM and rerun QUICK TEST.
9. Malfunction Indicator Light (MIL) or Shift Indicator Light (SIL). If shift indicator light is always on or off, go to «D6 - SHIFT INDICATOR LIGHT (SIL)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) , step 1). If malfunction indicator light is always on, go to «D11 - "CHECK ENGINE" LIGHT/MESSAGE (MALFUNCTION INDICATOR»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d11-check-engine-lightmessage-malfunction) , step 1). If malfunction indicator light is always off, go to «D11 - "CHECK ENGINE" LIGHT/MESSAGE (MALFUNCTION INDICATOR»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d11-check-engine-lightmessage-malfunction) , step 5). If MIL or SIL is working normally, replace ECA and repeat QUICK TEST.

D15 - CODE 15 KOEO CONTINUOUS

Note. Perform this CIRCUIT TEST when directed by other test procedures.

EEC Power Relay Circuit. Scheme 119

1. Continuous Memory Code 15 Displayed. Clear Continuous Memory Codes using procedure outlined in DIAGNOSIS & TESTING. Repeat KOEO SELF-TEST through Continuous Memory Code output. If continuous Code 15 is not displayed, continuous Code 15 testing is complete. If Continuous Memory Code 15 is displayed during retest, go to next step. NOTE: Continuous Memory Code 15 may be displayed when power to Keep Alive Memory (KAM) test pin No. 1 at ECA is interrupted. This code may be set when installing a breakout box. Code 15 may also be displayed the first time SELF-TEST is performed and power is restored to ECA. Repeat SELF-TEST to ensure correct diagnosis.
2. Engine Compartment Wire Routing. Ensure that EEC components and wiring are not close to high tension secondary voltage wires or ignition components. If EEC wiring is close to high tension wires, reroute EEC wiring. Repeat QUICK TEST. If Continuous Memory Code 15 is no longer displayed, Continuous Memory Code 15 testing is complete. If Continuous Memory Code 15 is still displayed, go to next step.
3. Checking Power Circuit For Keep Alive Memory (KAM). Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damaged pins and loose wires. Service as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Connect DVOM positive test lead to test pin No. 1 and negative test lead to pins No. 40 or 60 at the breakout box. Turn key on and observe voltage reading. If reading is less than 10.5 volts, repair open circuit. Repeat QUICK TEST. If reading is 10.5 volts or more, replace ECA and repeat QUICK TEST.

D16 - OUTPUT STATE CHECK NOT FUNCTIONING

Note. Perform this CIRCUIT TEST when directed by other test procedures.

Output State Check Circuit. Scheme 120

1. Checking Service Codes. Turn key off and wait 10 seconds. Perform KOEO SELF-TEST. If Codes 23, 53, 63 or 68 are displayed, go to «KOEO SELF-TEST»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes) table and service code(s) as instructed. If no codes are displayed, go to «D14 - NO CODES/CODES NOT LISTED»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d14-no-codescodes-not-listed) , step 1). If Code 11 (Pass) is displayed, go to next step.
2. Checking Throttle Linkage. Check throttle and linkage for sticking or binding. If throttle and linkage are okay, replace TPS and repeat QUICK TEST. If throttle and linkage are binding, repair as necessary and repeat QUICK TEST.

D17 - RE-INITIALIZATION CHECK

Note. Perform this CIRCUIT TEST when Codes 71, 72 or 78 is displayed or when directed by other test procedures.

Note. The electrical signatures of some aftermarket components may affect driveability of the vehicle.

EEC Power Relay Circuit. Scheme 121

1. Codes 71, 72 or 78: Checking For Electrical Noise Sources. Continuous Memory Code 72 or 78 indicates that power to the ECA was interrupted sometime during the last 40 warm-up cycle. A Continuous Code 71 indicates that sometime during the past 40 warm-up cycles, the ECA software requested a re-initialization or review of previous drive sequence data. This process could result in a driveability complaint. Possible causes for this fault or complaint are: Vehicle power interrupted to ECA. Spark plug wires incorrectly routed too close to ignition. High tension wire shielding removed. Electrical, radio, or motor static noise. Test pin No. 20 (case ground) not grounded to chassis. Open diodes on A/C or ISC relay. Turn key off. Ensure that EEC wiring and components are more than 2" (50 mm) away from secondary ignition wires. Make sure that EEC wiring and components are more than 4" (100 mm) away from distributor, ignition coil, and starter motor and its wiring. If these items are correct, go to next step. If not, correct as necessary and repeat QUICK TEST.
2. Checking Harness and Case Ground. Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 20 and chassis ground. If reading is less than 5 ohms, go to next step. If not, repair wiring harness and repeat QUICK TEST.
3. Case Ground Check With Harness Disconnected. Turn key off. Connect ECA to breakout box, but disconnect harness from breakout box. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 20 and ECA metal case. If reading is less than 5 ohms, go to next step. If reading is more than 5 ohms, replace ECA and repeat QUICK TEST.
4. "WIGGLE" Testing VPWR Circuit. With KOEO, connect DVOM to SELF TEST connector. Deactivate SELF-TEST. Using Continuous Monitor Mode, perform "WIGGLE" test on EEC-IV harness from ECA to power relay. If a fault is indicated or a Code 71 is displayed, repair intermittent in VPWR circuit. If no fault is indicated, inspect harness connections and pins. Replace power relay and rerun QUICK TEST.
5. Code 19: Internal Voltage. Code 19 indicates the ECA voltage regulator does not have the ability to maintain correct internal voltage. Run KOEO SELF-TEST, if Code 19-10-11 is present, replace ECA and rerun test. If Code 19-10-11 is not present, service other codes as indicated.

D18 - KEY POWER CHECK

Note. Perform this test ONLY when a Code 55 is displayed in QUICK TEST.

Key Power Circuits. Scheme 122

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: charging system overcharging, battery charger connected with engine running or jump starting vehicle.

1. Code 55: Checking Continuity of Key Power Circuit. Code 55 indicates key power circuit voltage is low. Possible causes for this fault are: circuit shorted to ground or faulty ECA. Turn key off and wait 10 seconds. Install breakout box and connect ECA. Disconnect the EEC-IV power relay or IRCM. Set DVOM on 200-ohm scale. Measure the following resistances: If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit, reconnect system components and rerun QUICK TEST.
2. Checking KEY POWER (KPWR) Circuit For Shorts to Ground. Turn key off, disconnect ECA and install breakout box. Disconnect power relay or IRCM. Set DVOM on 200K-ohm scale and measure resistance between test pin No. 5 and test pins No. 40, 46, and 60, at the breakout box. If resistance is greater than 10K ohms, replace ECA, reconnect components and retest system. If resistance is less than 10K ohms, repair short circuit and rerun QUICK TEST.

D19 - SYSTEM CHECK

Perform this test ONLY after Code 11 is displayed in KOEO SELF-TEST and you have been directed here from A1 - NO START or by DIAGNOSIS BY SYMPTOM TEST.

System Check Diagram. Scheme 123

Scheme 124

1. ISC-BPA Check. This step is for MPFI and SEFI vehicles with Stall or No Start faults. If engine stalls or if it does not start, attempt to start engine at part throttle. If engine will start and run smoothly at part throttle, go to «D5 - IDLE SPEED CONTROL (AIR BY-PASS)»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d5-idle-speed-control-air), step 4). If not, go to next step, except 2.3L Turbo MPFI engine equipped models, go to step 6).
2. Check Power to MAP/BP Sensor. Use Ford Motor Co. MAP/BP tester for this test. Turn key off and disconnect MAP/BP sensor. Connect MAP/BP tester between harness and MAP/BP sensor. Connect banana plugs of tester into DVOM and set DVOM on 20-volt scale. With tester connected, turn key on. If Green light is on, go to next step. If light is not on, repair open in VREF circuit, remove MAP/BP tester. Reconnect components and retest symptom. (Scheme 124): MAP/BP Tester & Circuit
3. MAP/BP Tester Output Reading. Measure several "known good" MAP sensors to obtain average measured voltage for specific location and date of testing. With MAP sensor connected and key on, measure SIGNAL voltage at MAP sensor. If voltage is in the correct range for your altitude, go to next step, except 2.3L Turbo MPFI engine equipped models, go to step 6). If voltage is not in the correct range for your altitude, replace MAP/BP sensor. MAP VOLTAGE OUTPUT Approx. Elevation (Ft.) Voltage Output (Volts) 0 1.55-1.63 1000 1.52-1.60 2000 1.49-1.57 3000 1.46-1.54 4000 1.43-1.51 5000 1.40-1.48 6000 1.37-1.45 7000 1.35-1.43
4. MAP/BP Engine Running Response Test. With key on, crank engine. If MAP/BP output voltage changes while cranking engine, go to step 6). If voltage does not change while cranking, go to next step.
5. Check Vacuum Lines. Check vacuum lines for correct routing, refer to Vehicle Emission Control Label. Check MAP sensor vacuum line for breaks, kinks or blockage. If vacuum lines are okay, replace MAP/BP sensor and retest. If vacuum lines are faulty, service as necessary and rerun QUICK TEST.
6. EGR Vacuum Check. Disconnect vacuum hose at EGR valve. DO NOT plug vacuum line. Start or attempt to start engine. If symptom is driveability related, check to see if vacuum is present at vacuum line. If vehicle is a "No Start", does engine start? If results are negative, go to next step. If results are positive, go to the following tests, depending on engine application: «D1 - EGR ON/OFF CONTROL»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d1-egr-onoff-control), step 1) for all 2.3L Turbo MPFI engine equipped models. «B4 - EGR VALVE POSITION SENSOR EGR CONTROL SOLENOID & EGR»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__b4-egr-valve-position-sensor) VENT SOLENOID, step 11) for all 2.3L OHC MPFI engine equipped models. «B10 - PRESSURE FEEDBACK EGR VALVE & EGR VACUM REGULATOR»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__b10-pressure-feedback-egr-valve), step 23) for all 2.3L HSC MPFI engine equipped models.
7. Checking EGR Valve. Inspect EGR valve for leaking. If valve is fully closed, go to «C1 - FUEL CONTROL - ALL APPLICATIONS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__c1-fuel-control-all), step 1). If EGR valve is leaking or not fully seated, replace or repair valve.

D20 - INTAKE AIR CONTROL VALVE (IAC) SYSTEM

Note. Perform this test only when service Code 81, is displayed during KOEO SELF-TEST or directed here by DIAGNOSIS BY SYMPTOM test.

IAC Circuit. Scheme 125

Scheme 126

Scheme 127

Scheme 128

1. Code 81: Check Solenoid Resistance. Code 81 indicates IAC solenoid output voltage did not change when IAC was activated during KOEO SELF-TEST. Possible causes for this fault are: IAC circuit open, shorted or disconnected or ECA output driver open or grounded. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale and disconnect IAC solenoid connector from harness. Measure resistance of solenoid. If resistance is 50-100 ohms, go to next step. If resistance is not 50-100 ohms, replace solenoid and rerun QUICK TEST. (Scheme 126): IAC Solenoid
2. Check Voltage of VPWR Circuit. With KOEO, disconnect IAC solenoid. Set DVOM on 20-volt scale. Measure voltage between VPWR circuit of IAC solenoid harness connector and battery negative post. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, reconnect IAC solenoid, repair open circuit in harness and rerun QUICK TEST.
3. Check Continuity of IAC Solenoid Circuit. Turn key off and wait 10 seconds. Disconnect 60-pin ECA connector. Inspect pins for corrosion or damage and service as necessary. Install breakout box, leave ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 32 at the breakout box and IAC harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit and rerun QUICK TEST.
4. Check For Short to Ground. Turn key off and wait 10 seconds. With breakout box installed and ECA disconnected, set DVOM on 200K-ohm scale. Disconnect IAC solenoid. Measure resistance between test pin No. 32 and test pins No. 40, 46 and 60 at the breakout box. If resistance is greater than 100K ohms, go to next step. If resistance is less than 100K ohms, repair short circuit, reconnect components and retest.
5. Check For Short to Power. Turn key off and wait 10 seconds. With breakout box installed and ECA disconnected, set DVOM on 200K-ohm scale. Disconnect IAC solenoid. Measure resistance between test pin No. 32 and test pins No. 37 and 57 at the breakout box. If resistance is greater than 100K ohms, replace ECA, reconnect components and retest. If resistance is less than 100K ohms, repair short circuit, reconnect components and retest. If fault is still present, replace ECA.
6. Checking Front and Rear Intake Air Valves. With key off, disconnect vacuum lines from both intake air valves. Check each air valve with a vacuum pump. Apply 10 in. Hg vacuum. If both valves hold vacuum, go to next step. If not, replace valve(s) as necessary and rerun QUICK TEST. (Scheme 127): Intake Air Valve Locations
7. Checking Air Valve Systems. With key off, apply 10 in. Hg to each air valve. If both valves and mechanical linkage move in response to the applied vacuum, go to next step. If valves and linkage are faulty, service as necessary and rerun QUICK TEST.
8. Check Vacuum to Intake Air Valves. With key off, check the vacuum lines from air valves to IAC solenoid. Inspect for damage or blockage. If vacuum lines are okay, go to next step. If vacuum lines are faulty, service as necessary and retest. (Scheme 128): Vacuum Line Routing
9. Check Vacuum Source to IAC Solenoid. Disconnect IAC solenoid vacuum supply hose from intake manifold. Start engine and check vacuum at the disconnected manifold hose. If vacuum is present at hose, replace IAC solenoid and rerun QUICK TEST. If vacuum is not present, check supply hose to IAC solenoid. Service as necessary and rerun QUICK TEST.

IAC Solenoid Vacuum Hose. Scheme 129

D21 - AXOD TRANSAXLE

Note. Perform this test only when service Codes 29, 39, 57, 59, 62, 67, 68, 69 or 89 are displayed.

AXOD Transaxle Circuits. Scheme 130

Note. All components must be connected for this test and the following AXOD DRIVE CYCLE TEST must be performed

1. Record and clear Continuous Memory Codes.
2. Warm engine to operating temperature.
3. With transaxle in "D" range, lightly accelerate from a stop to 40 MPH to allow transaxle to shift into 3rd gear. Hold speed and throttle opening steady for a minimum of 15 seconds (30 seconds above 4000 feet altitude).
4. Shift transaxle into overdrive and accelerate lightly from 40 to 50 MPH to allow transaxle to shift into 4th gear. Hold speed and throttle opening steady, in 4th gear, for a minimum of 15 seconds.
5. With transaxle in 4th gear, throttle open and speed steady, lightly apply and release brakes (enough to turn on brake lights). Hold speed and throttle opening steady for an additional 15 seconds.
6. Brake to a stop and remain stopped for a minimum of 20 seconds with transaxle in overdrive range. Perform KOEO SELF-TEST and record Continuous Memory Codes.

Scheme 131

Scheme 132

Scheme 133

Scheme 134

Scheme 135

Scheme 136

1. Continuous Memory Code 29 Displayed. Code 29 indicates insufficient input to the ECA from the Vehicle Speed Sensor (VSS). Possible causes for this fault are: faulty VSS, open or shorted circuit or faulty ECA. Perform AXOD DRIVE CYCLE TEST and return to this step. If Continuous Memory Code 29 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST for instructions. If there are none, test is complete. If Continuous Memory Code 29 is displayed, go to next step.
2. Checking Continuity of Vehicle Speed Sensor (VSS) Harness. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA and VSS disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 3 at the breakout box and VSS positive (+) circuit at harness connector. Measure resistance between test pin No. 6 and VSS negative (-) circuit at harness connector. If both readings are 5 ohms or more, repair open circuit(s) in VSS harness, then repeat step 1). If both readings are less than 5 ohms, go to next step.
3. Checking VSS Harness For Shorts to Power or Ground. With key off, ECA and VSS disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pin No. 3 and test pins No. 37, 40, and 6 at the breakout box. Measure resistance between test pin No. 6 and test pin No. 37 at the breakout box. If all readings are less than 10K ohms, repair short(s) in VSS harness, and repeat step 1). If all readings are more than 10K ohms, go to next step.
4. Repeat Drive Cycle With Substitute VSS Installed. Substitute original VSS with a good known VSS. With ECA and VSS connected, perform AXOD DRIVE CYCLE TEST and return to this step. If Continuous Memory Code 29 is displayed, replace ECA then repeat step 1). If Code 29 is not displayed, replace original VSS then repeat QUICK TEST.
5. Continuous Memory Code 69 Displayed. Perform AXOD DRIVE CYCLE TEST and return to this step. If Code 69 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST for instructions. If no codes are displayed, test is complete. If Continuous Memory Code 69 is still displayed, go to next step.
6. Checking Continuity of THS 3/2 Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 19 at the breakout box and THS 3/2 circuit at AXOD harness connector. If resistance is more than 5 ohms, repair open in THS 3/2 circuit then repeat step 5). If reading is 5 ohms or less, go to next step. (Scheme 131): AXOD Harness Connector (THS 3/2 Circuit)
7. Checking THS Circuit For Short to Power. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pin No. 19 and test pin No. 37. If reading is less than 10K ohms, repair short to power in THS 3/2 circuit, then repeat step 5). If reading is more than 10K ohms, go to next step.
8. Checking ECA Verification. With key off and breakout box installed, connect ECA and AXOD harness. Install a jumper wire between test pins No. 19 and No. 40 at the breakout box. Perform KOEO SELF-TEST. If Code 62 or 69 is displayed, remove jumper wire and go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis). If Code 62 or 69 is not displayed, remove jumper wire, replace ECA, and then repeat step 5).
9. Continuous Memory Code 59 Displayed. Perform AXOD DRIVE CYCLE TEST and return to this step. If Code 59 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST for instructions. If none, test is complete. If Code 59 is displayed, go to next step.
10. Checking Continuity of THS 4/3 Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 18 and THS 4/3 circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in THS 4/3 harness, then repeat step 9). If reading is 5 ohms or less, go to next step. (Scheme 132): AXOD Harness Connector (THS 4/3 Circuit)
11. Checking THS 4/3 Circuit For Short to Power. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200K-ohm scale. Measure resistance between pin No. 18 and test pin No. 37 at the breakout box. If reading is less than 10K ohms, repair short to power in THS 4/3 circuit, then repeat step 9). If reading is greater than 10K ohms, go to next step.
12. ECA Verification. With key off and breakout box installed, connect ECA and AXOD harness. Install a jumper wire between test pins No. 18 and 40. Perform KOEO SELF-TEST. If Code 62 or 59 is displayed, remove jumper wire and go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis). If Code 59 or 62 is not displayed, remove jumper wire, replace ECA, and then repeat step 10).
13. Continuous Memory Code 39 Displayed. Code 39 indicates AXOD converter by-pass clutch (lock-up) is not applying correctly. If Continuous Memory Code 59 is also present, go directly to step 9). Perform AXOD DRIVE CYCLE TEST then return to this step. If Continuous Memory Code 39 is still displayed, go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis). If Continuous Memory Code 39 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST for instructions. If no codes are displayed, test is completed.
14. Continuous Memory Code 57 Displayed. Code 57 indicates Neutral Pressure Switch (NPS) has failed in the open position. Possible causes for this fault are: open or short in NPS circuit, faulty ECA or faulty NPS. Perform AXOD DRIVE CYCLE TEST and then return to this step. If Continuous Memory Code 57 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST for instructions. If no codes are displayed, test is completed. If Continuous Memory Code 57 is still displayed, go to next step.
15. Checking Continuity of NPS Harness. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 30 and NPS circuit at AXOD harness connector. If resistance is more than 5 ohms, repair open in NPS circuit, then repeat step 14). If reading is 5 ohms or less, go to next step. (Scheme 133): AXOD Harness Connector (NPS Circuit)
16. Check NPS Circuit For Short to Power. With key off, install breakout box and disconnect ECA. Disconnect AXOD harness connector and set DVOM on 200K-scale. Measure resistance between test pin No. 30 and test pin No. 37 at the breakout box. If resistance is greater than 10K ohms, go to next step. If resistance is less than 10K ohms, repair short to power in NPS circuit, reconnect components and retest.
17. ECA Verification. With key off, install breakout box and connect ECA. Ensure AXOD harness is connected. Jumper test pin No. 30 to test pin No. 40 at the breakout box. Run KOEO SELF-TEST. If Code 67 is present, remove breakout box and go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis). If Code 67 is not present, replace ECA, reconnect components and repeat step 14).
18. Code 89 Displayed: Checking Continuity of VPWR Circuit. Code 89 indicates the Lock-Up Solenoid (LUS) signal indicates solenoid is always open or always closed. Possible causes for this fault are: open or shorted circuit, faulty ECA or faulty LUS. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 37 and VPWR circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in VPWR circuit then repeat QUICK TEST. If reading is 5 ohms or less, go to next step. (Scheme 134): AXOD Harness Connector (VPWR Circuit)
19. Check Continuity of LUS Circuit. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200 ohm scale. Measure resistance between test pin No. 53 and LUS circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in LUS circuit and then repeat QUICK TEST. If reading is 5 ohms or less, go to next step. (Scheme 135): AXOD Harness Connector (LUS Circuit)
20. Checking LUS Circuit For Power to Ground. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pin No. 53 and test pins No. 37 and 40 at the breakout box. If both resistances are less than 10K ohms, repair shorts in LUS circuit. Repeat QUICK TEST. If Code 89 is still displayed, replace ECA and repeat QUICK TEST. If both readings are greater than 10K ohms, go to next step.
21. Checking Total Circuit Resistance. With key off, breakout box installed, and ECA disconnected, connect AXOD harness. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 53 and test pin No. 57. If resistance is between 20 and 40 ohms, replace ECA and repeat QUICK TEST. If resistance is not between 20 and 40 ohms, go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis).
22. Code 62: AXOD Harness Verification. Code 62 indicates 4/3 or 3/2 pressure switch signal indicates switch has failed in the closed position. Possible causes for this fault are: short in THS 4/3 or THS 3/2 circuit, faulty ECA, faulty THS 4/3 or 3/2 pressure switch. Turn key off and disconnect AXOD harness. Perform KOEO SELF-TEST and record codes. If Code 62 is still displayed, fault is in THS 4/3 circuit. Go to next step. If Code 62 is not displayed, remove test equipment and go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis).
23. Checking THS 3/2 and 4/3 Circuits For Short to Ground. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box and leave ECA disconnected. Leave AXOD harnesses disconnected. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 18 and test pins No. 40 and 60. Also measure resistance between test pin No. 19 and test pins No. 40 and 60. If all readings are less than 10K ohms, repair short(s) to ground. Repeat QUICK TEST. If all readings are greater than 10K ohms, replace ECA and repeat QUICK TEST.
24. Code 59: AXOD Harness Verification. Code 59 indicates THS 4/3 pressure switch circuit has failed in the closed position. Possible causes for this fault are: short in THS 4/3 circuit, faulty ECA or faulty THS 4/3 pressure switch. Turn key off and disconnect AXOD Harness. Run KOEO SELF-TEST. If Code 59 is displayed, go to next step. If Code 59 is not displayed, go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis).
25. Checking THS 4/3 Circuit For Short to Ground. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leave ECA and AXOD harness connector disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 18 and test pins No. 40 and 60. If readings are greater than 10K ohms, remove breakout box, replace ECA and rerun QUICK TEST. If reading is less than 10K ohms, repair short in ECA and rerun QUICK TEST.
26. Code 69: Checking AXOD Harness. Code 69 indicates THS 3/2 pressure switch circuit is failed in the closed position. Possible causes for this fault are: short in THS 3/2 circuit, faulty ECA or faulty 3/2 pressure switch. With key off, disconnect AXOD harness. Perform KOEO SELF-TEST. If Code 69 is still displayed, go to next step. If Code 69 is not displayed, go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis).
27. Checking THS 3/2 Circuit For Short to Ground. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box and leave ECA disconnected. Disconnect AXOD harness and set DVOM on 200K-ohm scale. Measure resistance between test pin No. 19 and test pins No. 40 and 60 at the breakout box. If all readings are less than 10K ohms, repair short to ground and repeat QUICK TEST. If all readings are greater than 10K ohms, replace ECA and rerun QUICK TEST.
28. Code 67: Checking Voltage at NPS Input to ECA. Code 67 indicates that NPS circuit has failed closed or input to A/C clutch circuit is closed. Possible causes for this fault are: short in NPS circuit, or faulty ECA or NPS. With KOEO, disconnect ECA and inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box and reconnect ECA. Set DVOM on 20-volt scale. Measure voltage between test pins No. 30 and 46 at breakout box. If voltage is less than 4 volts, go to next step. If voltage is more than 4 volts, go to «B13 - NEUTRAL DRIVE SWITCH (NDS) A/C INPUT»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__b13-neutral-drive-switch-nds), step 9).
29. Checking NPS Harness Circuit For Shorts to Ground. Turn key off. Install breakout box and disconnect ECA and AXOD harness. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 30 and test pins No. 40 and 60 at the breakout box. If resistances are greater than 10K ohms, go to next step. If resistances are less than 10K ohms, repair ground short in NPS circuit and rerun QUICK TEST.
30. Checking ECA. Turn key off and install breakout box. Reconnect ECA. Disconnect AXOD harness and run KOEO SELF-TEST. If Code 67 is displayed, replace ECA and rerun QUICK TEST. If Code 67 is not displayed, go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis).
31. Code 68: Checking Continuity of TTS Harness Circuit. Code 68 indicates Transmission Temperature Switch (TTS) circuit is failed open. Possible causes for this fault are: open or shorted TTS circuit, faulty ECA or TTS. Turn key off and wait 10 seconds. Disconnect AXOD harness. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 44, at the breakout box, and TTS terminal of AXOD harness connector. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open circuit in TTS circuit and road test vehicle to verify complaint. (Scheme 136): AXOD Harness Connector (TTS Circuit)
32. Checking TTS Harness For Short to Power or Ground. Turn key off and wait 10 seconds. Disconnect ECA and AXOD harness. Install breakout box and set DVOM on 200K-ohm scale. Measure resistance between test pin No. 44 and test pin No. 37 at the breakout box. Measure resistance between test pins No. 44 and 40 at the breakout box. If resistance is greater than 10K ohms, go to next step. If resistance is less than 10K ohms, repair short in TTS circuit and rerun QUICK TEST.
33. Checking ECA Operation. With key off and breakout box installed, connect ECA and AXOD harness. Jumper between test pins No. 44 to No. 40 at the breakout box. Perform KOEO SELF-TEST. If Code 68 is still present, reconnect components and go to «D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d24-axod-electrical-system-diagnosis). If complaint is still present, replace ECA, reconnect components and retest.

D22 - A4LD TRANSMISSION

Note. Perform this test only when Code 86 or 89 is displayed or referred here by other chart or test procedure. To prevent replacement of good components be aware that the following non-EEC areas may be at fault

Scheme 137

1. Hydraulic or emergency brake system
2. Transmission linkage
3. Internal transmission components (Scheme 137): A4LD Transmission Circuits

1. Code 86 or 89: Circuit Identification. Code 86 indicates ECA did not see a voltage drop when the Shift Solenoid (SS) was activated. Possible causes for this fault are: SS resistance out of limits, SS circuit open or grounded or faulty ECA. Code 89 indicates ECA did not see a voltage drop when the CCO solenoid was activated. Possible causes for this fault are: Converter Clutch Override resistance is out of limits, CCO circuit open or grounded or faulty ECA. Enter this test step for KOEO codes. Verify codes match appropriate transmission solenoid circuit. TRANSMISSION SOLENOID CIRCUITS Solenoid Type ECA Signal Output Pin KOEO Code Converter Clutch Override (CCO) 53 89 Shift Solenoid (SS) 3/4-4/3 52 86 If any of the above codes are present, go to next step. If not, service other codes as necessary.
2. Checking Resistance of A4LD Solenoid. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 37 and 57 and ECA signal output pin at the breakout box. If the resistance is 26 to 40 ohms, go to step 5). If resistance is not 26-40 ohms, go to next step.
3. Check Continuity of Transmission Solenoid Harness. With key off, install breakout box. Leave ECA and transmission bulkhead connector (A4LD solenoids) disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 37 and 57 at the breakout box and VPWR circuit pin of the harness connector at the transmission. Measure resistance between the ECA signal output pin No. 52 at the breakout box and SS pin of the harness connector at the transmission.
4. Check For Shorts to Power or Ground of A4LD Solenoid Harness. With key off, install breakout box, leaving ECA disconnected. Disconnect transmission bulkhead connector. Set DVOM on 200K-ohm scale. Measure resistance between the ECA signal output pin and test pins No. 37 and 57 at the breakout box. Measure resistance between the ECA signal output pin and test pins No. 40, 60 and 46 at the breakout box and at chassis ground. If all resistances are greater than 10K ohms, go to next step. If any resistance is less than 10K ohms, repair short circuit, reconnect components and rerun QUICK TEST.
5. Check VPWR Voltage to Transmission Solenoids. With key off, breakout box installed and ECA connected, set DVOM on 20-volt scale. Disconnect transmission bulkhead connector. Turn key on, leaving engine off. Measure voltage between test pins No. 37 and 57 at the bulkhead connector and chassis ground. If voltage is greater than 10.5 volts, repair or replace transmission solenoid as necessary. If voltage is less than 10.5 volts, replace ECA, reconnect components and rerun QUICK TEST.

D23 - INTEGRAL RELAY CONTROL MODULE (IRCM)

Note. Perform this test only when KOEO SELF-TEST Codes 72, 78, 82, 83, 87, 88, 95 or 96 are displayed, or when you are directed here by A1 - NO START , A3 - REFERENCE VOLTAGE , or by DIAGNOSIS BY SYMPTOM TEST.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuel lines and fuel filters, contaminated fuel, fuel pump, ignition switch, battery cables and ground straps, alternator and voltage regulator, A/C clutch or A/C demand, and cooling fan motor.

1. Checking Battery Supply Voltage. With KOEO, set DVOM on 20-volt scale. Measure voltage across battery terminals. If reading is less than 10.5 volts, service or replace discharged battery. If reading is 10.5 volts or more, go to next step.
2. Checking Battery Ground. With KOEO, and ECA connected, set DVOM on 20-volt scale. Measure voltage between negative battery post and SIGNAL RETURN circuit in SELF-TEST connector. If reading is less than .5 volt, go to step 6). If reading is .5 volt or more, go to next step.
3. Isolating Ground Fault. Turn key off. Disconnect ECA 60 pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between negative battery post and test pins No. 40 and 60. If one or both readings are .5 volt or more, repair open in circuit(s) and repeat QUICK TEST. If both readings are less than .5 volt, go to next step.
4. ECA Ground Fault Isolation. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, set DVOM on 200-ohm scale. Measure resistance between test pins No. 46 and 40, and between test pins No. 46 and 60. If one or both readings are 5 ohms or more, disconnect ECA connector. Inspect connector for damage, repair if necessary and repeat this step. If fault is still present, replace ECA and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.
5. Checking Continuity of Signal Return Circuit. Turn key off and wait 10 seconds. With breakout box and ECA connected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and SIGNAL RETURN circuit at SELF-TEST connector. If reading is less than 5 ohms, system is okay. Repeat QUICK TEST. If reading is 5 ohms or more, correct cause of high resistance in SIGNAL RETURN circuit. Repeat QUICK TEST.
6. Measure Voltage and Ground to IRCM. Turn key off and disconnect Integral Relay Control Module (IRCM). Set DVOM on 20-volt scale. Measure voltage between IRCM harness connector pin No. 8 (battery positive) and pin No. 15 (ground). If reading is less than 10.5 volts, go to step 9). If reading is 10.5 volts or more, go to next step.
7. Key Power to IRCM. With key off, disconnect IRCM and set DVOM on 20-volt scale. Turn key on. Measure voltage between pins No. 13 (+) and 15 (-) at IRCM harness connector. If reading is less than 10.5 volts, repair open between pin No. 13 and ignition switch. Connect IRCM and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
8. Checking Continuity of VPWR Circuit. Turn key off. Disconnect IRCM and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 37 and 57 at the breakout box to IRCM harness connector pin No. 24. If reading is 5 ohms or more, repair open in VPWR circuit. Connect IRCM and repeat QUICK TEST. If reading is less than 5 ohms, replace IRCM and repeat QUICK TEST.
9. Checking Continuity of Power Ground to IRCM. With key off and IRCM disconnected, set DVOM on 200-ohm scale. Measure resistance from negative battery post to IRCM harness connector pin No. 15. If reading is 5 ohms or more, repair open in ground circuit to IRCM harness connector pin No. 15. Repeat QUICK TEST. If reading is less than 5 ohms, repair open in battery positive to pin No. 8 of IRCM harness connector. Repeat QUICK TEST.
10. Code 72: Intermittent Open in VPWR Circuit. Code 72 indicates that while key power was present voltage to the IRCM was interrupted, or electrical noise caused the ECA to reset. Driveability problems such as, stalling, high idle, lack of power on acceleration or other drive symptoms could result. Possible causes for this fault are: intermittent open in VPWR circuit between IRCM and ECA, intermittent fault in EEC power relay, intermittent open in VBAT circuit of IRCM, intermittent open in KEY POWER circuit or EEC harness too close to spark plug wires. Using CONTINUOUS MONITOR MODE (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while wiggling, bending, or twisting harness from IRCM to ECA and from ignition switch to battery positive terminal. If fault is indicated or if Code 72 reappears, repair intermittent fault in VPWR circuit and repeat QUICK TEST. If fault is not found or if codes do not reappear, inspect all component and harness connectors for damaged pins, corrosion, or loose wires. Repair if necessary. If okay, replace IRCM and repeat QUICK TEST.
11. Checking Power to Fuel Pump(s). With KOEO, locate and disconnect fuel pump(s). Set DVOM on 20-volt scale. Measure voltage between CHASSIS GROUND and POWER-to-PUMP circuit at fuel pump while cranking engine. If reading is 8.0 volts or more, service electric fuel pump system. If reading is less than 8.0 volts, go to next step.
12. Checking Power-to-Pump Circuit Continuity. With key off and DVOM on 200-ohm scale, disconnect IRCM and fuel pump(s). Measure resistance between IRCM harness connector pin No. 5 and POWER-to-PUMP circuit at harness connector at fuel pump(s). If reading is less than 5 ohms, replace IRCM. Connect all components and repeat QUICK TEST. If reading is 5 ohms or more, repair open in POWER-to-PUMP circuit. Connect IRCM and repeat QUICK TEST.
13. Checking Power-to-Pump Circuit For Shorts to Power. With key off and DVOM on 200K-ohm scale, disconnect IRCM and fuel pump(s). Measure resistance between pin No. 5 and pin No. 24 at IRCM harness connector. Measure resistance between pin No. 5 at the IRCM harness connector and battery positive post. If any reading is less than 10K ohms, repair short circuit. Connect all components and attempt to start vehicle. If vehicle runs, repeat QUICK TEST. If vehicle does not run, replace IRCM and repeat QUICK TEST. If all readings are 10K ohms or more, replace IRCM and repeat QUICK TEST.
14. Code 83 or 87: Checking Continuity of Fuel Pump Circuit. Code 83 or 87 indicates voltage output for the high or low fuel pump circuit did not change when activated during KOEO SELF-TEST. Possible causes for this fault are: open or grounded fuel pump circuit, open or grounded ECA driver or disconnected or open solenoid. Turn key off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect IRCM and set DVOM on 200-ohm scale. Code 83: Measure resistance of fuel pump(s) circuit, from test pin No. 22 at the breakout box to IRCM harness connector pin No. 18. Code 87: Measure resistance between test pin No. 41 at the breakout box and pin No. 11 at the IRCM harness connector. If reading is 5 ohms or more, repair open in fuel pump circuit. Connect all components and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
15. Checking Fuel Pump Circuit For Shorts to Ground. With key off, breakout box installed, and ECA and IRCM disconnected, set DVOM on 200K-ohm scale. Code 87: Measure resistance between test pin No. 22 and test pins No. 37, 57, and battery positive post. Measure resistance between test pins No. 22, 40, and 60, and battery negative terminal. Code 83: Measure resistance between test pin No. 41 and test pins No. 37, 57, and battery positive post. Measure resistance between test pins No. 41 and test pins No. 40, 60, and battery negative terminal. If any reading is less than 10K ohms, repair fuel pump(s) circuit shorts to power or ground. Connect all components and repeat QUICK TEST. If Code 83 or 87 is still present, go to next step. If all readings are 10K ohms or more, go to next step.
16. Checking Fuel Pump Relay Coil Resistance. Turn key off. Disconnect IRCM and set DVOM on 200-ohm scale. Disconnect ECA and install breakout box. Measure resistance of IRCM between pins No. 18 and 24 or pins No. 11 and 24. If resistance is between 65 and 100 ohms, replace ECA. Connect all components and repeat QUICK TEST. If resistance is not between 65 and 100 ohms, replace IRCM. Connect all components and repeat QUICK TEST.
17. No Fan Operation. Turn key off. Disconnect IRCM and set DVOM on 20-volt scale. Measure voltage between battery negative post and IRCM harness connector pins No. 1, 2, 6, and 7. If any reading is less than 10.5 volts, service open in power circuit. Re-evaluate symptom. If all readings are 10.5 volts or more, go to next step.
18. Checking Fan Motor Operation. Turn key off and disconnect IRCM connector. Install a jumper wire between IRCM harness connector pins No. 3 and 6. If cooling fan does not run, go to step 20). If cooling fan runs, go to next step.
19. Checking Fan Low Speed. Turn key off. Connect IRCM and disconnect ECA. Turn key on. If fan does not run at low speed, replace IRCM. Connect ECA and re-evaluate symptom. If fan runs at low speed, go to step 22).
20. Measuring Voltage Supply at Fan. With key off, disconnect cooling fan and IRCM. Install a jumper wire between IRCM harness connector pins No. 3 and 6. Set DVOM on 20-volt scale and measure voltage at cooling fan harness connector. If reading is 8.0 volts or more, replace cooling fan motor and re-evaluate symptom. If reading is less than 8.0 volts, go to next step.
21. Checking Cooling Fan Ground Circuit. Turn key off. Disconnect cooling fan and IRCM. Install a jumper wire between IRCM harness connector pins No. 3 and 6. Set DVOM on 20-volt scale. Measure voltage between positive terminal at cooling fan harness connector and battery negative post. If reading is 8 volts or more, repair open in ground circuit to fan. After repairs, connect IRCM and re-evaluate symptom. If reading is less than 8 volts, repair open in power-to-fan circuit from pins No. 3 and 4 of IRCM harness connector to cooling fan connector. After repairs, connect IRCM and re-evaluate symptom.
22. Connecting High Speed Electric-Drive Fan Signal (HEDF) to Ground. Turn key off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Turn key on. With IRCM connected, install a jumper wire between test pins No. 52 and 40. If fan does not run at high speed, replace IRCM. Connect ECA and re-evaluate symptom. If fan runs at high speed, go to next step.
23. Checking ECT Sensor. Connect ECA and check engine coolant level. Warm engine to normal operating temperature. Turn key off and wait 10 seconds. Disconnect Engine Coolant Temperature (ECT) sensor harness. Set DVOM on 200K-ohm scale. Measure resistance of ECT sensor. If reading is between 1500 and 2000 ohms, replace ECA. Connect all components and re-evaluate symptom. If reading is not between 1500 and 2000 ohms, replace ECT sensor. Connect all components and re-evaluate symptom.
24. Checking A/C Pressure Switch Harness Continuity. With key off, install breakout box and connect ECA. Disconnect A/C pressure switch. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 2 at the breakout box and A/C pressure switch circuit at the harness connector. Measure resistance between test pin No. 46 at the breakout box and SIGNAL RETURN at the A/C pressure switch harness connector. If both resistances are less than 5 ohms, go to next step. If resistances are greater than 5 ohms, remove breakout box, repair open circuit and rerun QUICK TEST.
25. Checking HEDF Operation. With key off, disconnect A/C pressure switch. Jumper A/C pressure circuit to SIGNAL RETURN at the switch vehicle harness connector. Turn key on. If HEDF is on, replace A/C pressure switch. If HEDF is not on, replace ECA, reconnect components and rerun QUICK TEST.
26. Code 83 Displayed: Check HEDF Circuit Resistance. Code 83 indicates a failed HEDF circuit. Turn key off and disconnect IRCM. Set DVOM on 200-ohm scale. Measure resistance of IRCM between pins No. 17 and 24. If reading is not between 50 and 100 ohms, replace IRCM and repeat QUICK TEST. If reading is between 50 and 100 ohms, go to next step.
27. Checking HEDF ECA Signal to IRCM For Open. Turn key off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200-ohm scale and measure continuity between test pin No. 52 and IRCM harness connector pin No. 17. If reading is greater than 5 ohms, repair open in HEDF circuit. Connect all components and repeat QUICK TEST. If reading is 5 ohms or less, go to next step.
28. Checking HEDF Circuit For Shorts to Ground. With key off, breakout box installed, and ECA and IRCM disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pins No. 52 and 40. If reading is 10K ohms or less, repair short to ground in HEDF circuit. Reconnect components and repeat QUICK TEST. If reading is greater than 10K ohms, go to next step.
29. Checking HEDF Circuit For Short to Power. With key off, breakout box installed, and ECA and IRCM disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pins No. 52 and 37. If reading is more than 10K ohms, replace ECA. Connect all components and repeat QUICK TEST. If reading is 10K ohms or less, repair short to power. Connect all components and repeat QUICK TEST. If Code 83 is still present, replace ECA and repeat QUICK TEST.
30. Low Speed Fan Always On. Turn key off. Disconnect ECA 60 pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect IRCM and set DVOM on 200-ohm scale. Measure resistance between test pin No. 55 and IRCM harness connector pin No. 14. If reading is more than 5 ohms, repair open in EDF circuit. Connect all components and re-evaluate symptom. If reading is 5 ohms or less, go to next step.
31. Checking EDF Circuit For Shorts to Power. With key off, breakout box installed, and ECA and IRCM disconnected, set DVOM on 200K-ohm scale. Measure resistance between test pins No. 55 and 37, and from test pin No. 55 to battery positive post. If reading is 10K ohms or less, repair short to power in EDF circuit, and then go to next step. If reading is more than 10K ohms, go to next step.
32. Checking EDF Circuit For Short to Ground. With key off, breakout box installed and ECA disconnected, connect IRCM. Install a jumper wire between test pin No. 55 and test pins No. 40 or 60 (ground). If cooling fan continues to run, replace IRCM, reconnect components and re-evaluate symptom. If cooling fan stops running, replace ECA. Re-evaluate symptom.
33. Check A/C Pressure Switch Input. With key off, disconnect vehicle harness at A/C pressure switch. Turn key on. If fan still runs, reconnect components and go to next step. If fan does not run, replace A/C pressure switch and re-evaluate symptom.
34. Check A/C Pressure Switch For Short to Ground. With key on, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect IRCM and set DVOM on 200K-ohm scale. Measure resistance between test pin No. 2 and test pins No. 40, 46 and 60. If resistance is less than 10K ohms, repair short circuit, remove breakout box and reconnect components. Re-evaluate system. If resistance is greater than 10K ohms, go back to step 30).
35. Checking Fan Voltage. Turn key off. Disconnect IRCM and set DVOM on 20-volt scale. Measure voltage between battery negative post and pins No. 1 and 2 at IRCM harness connector. If readings are less than 10.5 volts, repair open in power circuit and re-evaluate symptom. If reading is 10.5 volts or more, go to next step.
36. Checking Fan Motor. Turn key off and disconnect IRCM connector. Install a jumper wire between IRCM harness connector pins No. 1 and 3. If cooling fan does not run, go to step 38). If cooling fan runs, go to next step.
37. Checking Fan Run Mode. With key off and ECA disconnected, connect IRCM. Turn key on. If cooling fan does not run, go to step 39). If cooling fan runs, go to step 41).
38. Measure Battery Voltage at Fan: By-Pass IRCM. Turn key off. Disconnect cooling fan harness and IRCM connector. Install a jumper wire between IRCM harness connector pins No. 1 and 3. Set DVOM on 20-volt scale and measure voltage at cooling fan harness connector. If reading is 8.0 volts or more, replace cooling fan and re-evaluate symptom. If reading is less than 8.0 volts, go to step 40).
39. Checking EDF Circuit For Short to Ground. Turn key off. Disconnect ECA and IRCM. Set DVOM on 200K-ohm scale and measure resistance between IRCM harness connector pins No. 14 and 15. If resistance is 10K ohms or more, replace IRCM. Connect all components and re-evaluate symptom. If reading is less than 10K ohms, repair short to ground in EDF circuit. Connect all components and re-evaluate symptom.
40. Checking Cooling Fan Ground Circuit. Turn key off and disconnect cooling fan. Disconnect IRCM connector. Install a jumper wire between IRCM harness connector pins No. 1 and 3. Set DVOM on 20 volt scale and measure voltage between cooling fan harness connector and battery negative terminal. If reading is 8.0 volts or more, repair open in fan ground circuit. Connect IRCM and re-evaluate symptom. If reading is less than 8.0 volts, repair open in power-to-fan circuit from IRCM harness connector pins No. 3 and 4 to cooling fan connector. Connect IRCM and re-evaluate symptom.
41. Checking ECT Sensor. Connect ECA and check engine coolant level. Warm engine to normal operating temperature. Turn key off and wait 10 seconds. Disconnect ECT sensor. Set DVOM on 200K-ohm scale and measure resistance of ECT sensor. If reading is between 1500 and 2000 ohms, replace ECA. Connect all components and re-evaluate symptom. If reading is not between 1500 and 2000 ohms, replace ECT sensor. Connect all components and re-evaluate symptom.
42. Checking Voltage at A/C Clutch. Turn key on, leaving engine off. Place A/C demand switch to A/C "ON" position. Set DVOM on 20-volt scale and check voltage at A/C clutch harness connector. If voltage reading is 10.5 volts or more, service A/C compressor and/or system. If voltage is less than 10.5 volts, go to next step.
43. Checking Continuity of IRCM to A/C Clutch Circuit. Turn key off and disconnect IRCM connector. Set DVOM on 200-ohm scale. Measure resistance between IRCM harness connector pin No. 23 and power circuit terminal pin at A/C clutch harness connector. Also measure resistance between IRCM harness connector pin No. 16 and ground circuit at A/C clutch harness connector. If readings are more than 5 ohms, repair open in power or ground A/C circuit(s) and re-evaluate symptom. If readings are 5 ohms or less, go to next step. NOTE: DO NOT use diagnostic tester in step 44), use VOM/DVOM only. Enter OUTPUT STATE CHECK as specified in test. For additional information see DIAGNOSTIC AIDS, OUTPUT STATE CHECK in front of this article.
44. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. After inspection, reconnect breakout box and ECA. Set DVOM on 20-volt scale. Connect DVOM negative test lead to Self-Test Output (STO) and positive lead to battery positive terminal. Using jumper wire, connect Self-Test Input (STI) to signal return at SELF-TEST connector. Perform KOEO SELF-TEST until completion of CONTINUOUS SELF-TEST codes (DVOM will read zero volts). DVOM should change to a high voltage reading. If DVOM did not change, depress throttle to WOT and release. If STO voltage still does not go high, go to «D16 - OUTPUT STATE CHECK NOT FUNCTIONING»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d16-output-state-check-not) , step 1). If DVOM changes, remain in OUTPUT STATE CHECK and go to next step.
45. Checking WAC Output Operation. With KOEO, place A/C demand switch to A/C "ON" position. Set DVOM on 20-volt scale. Connect DVOM positive test lead to pin No. 37 and negative test lead to test pin No. 54. While observing DVOM, depress and release throttle several times (to cycle output on and off). If voltage output does change, go to step 47). If voltage output changes, go to next step.
46. Checking Voltage at A/C Clutch Switch. With key on, engine off and A/C demand switch in A/C "ON" position, verify that breakout box is installed and that ECA and IRCM are connected. Set DVOM on 20-volt scale and measure voltage between test pins No. 10 and 40. If reading is less than 10.5 volts, go to step 48). If reading is 10.5 volts or more, go to next step.
47. Checking Continuity of ACCS to IRCM Circuit. Turn key off and wait 10 seconds. Disconnect ECA and IRCM connectors. Set DVOM on 200-ohm scale and measure resistance between test pin No. 10 and IRCM harness connector pin No. 21. If reading is more than 5 ohms, service open in ACCS circuit and re-evaluate symptom. If reading is 5 ohms or less, replace IRCM and re-evaluate symptom.
48. Checking ACCS Circuit Continuity. Turn key off and wait 10 seconds. Place A/C demand switch to A/C "ON" position. Set DVOM on 200-ohm scale and measure resistance between test pin No. 10 and A/C demand switch. If reading is 5 ohms or less, EEC system is okay. Service A/C system. If reading is more than 5 ohms, repair open in switch circuit. Repeat QUICK TEST.
49. Checking Continuity in WAC to IRCM Circuit. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200-ohm scale and measure resistance between test pin No. 54 and IRCM harness connector pin No. 22. If reading is more than 50 ohms, repair open in WAC circuit and re-evaluate symptom. If reading is 50 ohms or less, go to next step.
50. Checking WAC Circuit For Shorts to Ground. Turn key off and wait 10 seconds. Leave breakout box installed, and ECA disconnected. Disconnect IRCM connector. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 54 and 40, and between test pins No. 54 and 46, and between test pin No. 54 and battery negative post. If any reading is less than 10K ohms, repair shorts to ground in WAC circuit and re-evaluate symptom. If all readings are 10K ohms or more, go to next step.
51. Checking WAC Circuit For Short to Power. Turn key off and wait 10 seconds. Leave breakout box installed, and ECA disconnected. Disconnect IRCM connector. Set DVOM on 200K-ohm scale. Measure resistance between test pins No. 54 and 37, and between test pin No. 54 and battery positive post. If any reading is less than 10K ohms, repair shorts to power in WAC circuit and then go to next step. If all readings are 10K ohms or more, go to next step.
52. Checking Voltage at A/C Clutch. Turn key off and wait 10 seconds. Leave breakout box installed, and ECA disconnected. Connect IRCM connector and disconnect A/C clutch harness. Place A/C demand switch to A/C "ON" position. With KOEO, set DVOM on 20-volt scale and measure voltage at A/C clutch harness connector. If reading is more than 10.5 volts, replace ECA and re-evaluate symptom. If reading is less than 10.5 volts, replace IRCM and re-evaluate symptom.
53. Code 88: Checking EDF Signal to IRCM For Short to Ground. If fan is always on with Code 88, go to step 55). With key off, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200K-ohm scale and measure resistance between test pins No. 40 and 55. If reading is 10K ohms or less, repair short to ground in EDF circuit. Connect all components and repeat QUICK TEST. If reading is more than 10K ohms, go to next step.
54. Check Fan Running Mode. With key off and breakout box installed, disconnect ECA and connect IRCM connector. Turn key on. If fan runs as indicated, replace ECA. Connect all components and repeat QUICK TEST. If fan does not run as indicated, replace IRCM. Connect all components and repeat QUICK TEST.
55. Code 88: Check EDF Signal to IRCM For Open Circuit. Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200-ohm scale and measure resistance between breakout box test pin No. 55 and pin No. 14 at IRCM harness connector. If reading is 5 ohms or less, go to next step. If not, repair open in EDF circuit. Connect all components and repeat QUICK TEST.
56. Checking EDF Circuit For Short to Power. Turn key off. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200K-ohm scale. Measure resistance between test pins No. 55 and 37, and from test pin No. 55 to battery positive terminal. If readings are 10K ohms or less, repair short to power in EDF circuit. After repairs, go to next step. If readings are greater than 10K ohms, go to next step.
57. Checking EDF For Shorts to Ground. Turn key off. Install breakout box, leaving ECA disconnected. Ensure IRCM is properly connected. Turn key on. Using jumper wire, connect test pin No. 55 to test pins No. 40 or 60. If fan continues to run, replace IRCM. Connect all components and repeat QUICK TEST. If fan does not run, replace ECA. Connect all components and repeat QUICK TEST.
58. Code 95: Check Inertia Switch. A KOEO SELF-TEST Code 95 indicates one of the following: Open circuit in fuel pump or between fuel pump and FPM circuit. Poor fuel pump ground connection. Short in fuel pump power circuit. Fuel pump relay contacts always closed. Turn key off and wait 10 seconds. Locate and disconnect fuel pump inertia switch. Set DVOM on 200-ohm scale. Measure resistance of fuel pump inertia switch. If resistance is less than 5 ohms, reconnect inertia switch and go to next step. If resistance is more than 5 ohms, replace or reset inertia switch, rerun QUICK TEST.
59. Checking That Fuel Pump is Off. Turn key off. Listen for fuel pump. If pump is still running go to next step. If pump is off, go to step 61).
60. Checking For Closed Fuel Pump Relay. With key off, locate and disconnect IRCM. If fuel pump shuts off when controller is disconnected, replace IRCM and rerun QUICK TEST. If pump does not shut off, repair short in POWER-to-PUMP (FPM) circuit. Rerun QUICK TEST.
61. Checking Continuity of FPM Circuit. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200 ohm scale and measure resistance between FPM circuit at the breakout box and IRCM harness pin No. 5. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit and rerun QUICK TEST.
62. Checking FPM Circuit Ground Continuity. With key off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200 ohm scale and measure resistance between FPM circuit at breakout box and battery negative terminal. If resistance is less than 5 ohms, replace ECA, reconnect and test system. If resistance is greater than 5 ohms, repair fuel pump circuit or replace fuel pump and rerun QUICK TEST.
63. Code 59 or 96: Fuel Pump Power Circuit Continuity. A Code 59 or 96 indicates that when fuel pump is activated, no power is supplied to pump. Turn key off and wait 10 seconds. Disconnect ECA 60 pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Disconnect IRCM connector. Set DVOM on 200-ohm scale and measure resistance between FPM circuit at breakout box and IRCM harness connector pin No. 5. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in power to pump circuit between FPM splice and IRCM. Rerun QUICK TEST.
64. Checking Fuel Pump Operation. With key off, disconnect ECA 60-pin connector. Install breakout box, reconnect ECA and IRCM. Set DVOM on 20-volt scale. Connect DVOM between FPM circuit and test pin No. 40, at the breakout box. Observe DVOM and turn key to "ON" position. If voltage is 10.5 or more volts, for approximately one second after key is turned on, replace ECA and rerun QUICK TEST. If voltage does not increase to specification, replace IRCM and rerun QUICK TEST.
65. Continuous Memory Code 95: Checking EEC-IV Harness. A Code 95 indicates that there is an open circuit in the fuel pump or between the fuel pump and FPM circuit in the ECA. The fuel pump ground circuit is poor. Start engine and test for stalling or stumble while performing "WIGGLE" test on fuel pump and ECA harness. Perform "WIGGLE" test on fuel pump ground circuit. Lightly tap on fuel pump to duplicate road shock. Turn key off and inspect connections for corrosion or damage. If no fault is found, go to next step. If fault is found, repair it, clear memory codes, and retest.
66. Checking FPM Circuit. Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. With KOEO, connect a test light between FPM circuit and test pin No. 37. Observe test light while performing "WIGGLE" test on the monitor circuit (pin No. 8) between the ECA and the connection at the power to pump circuit. If a fault is found, isolate and repair. Clear memory codes and rerun QUICK TEST. If no fault is found, fault cannot be duplicated at this time. Clear memory codes for future testing.
67. Continuous Memory Code 59 or 96: Check For Code 83 or 87 Also Displayed. If Code 83 or 87 is also present, go to step 69). If Code 83 or 87 is not present, go to next step.
68. Checking EEC-IV Harness. A Continuous Memory Code 59 or 96, without the presence of a Continuous Memory Code 83 or 87, indicates that during vehicle operation the fuel pump relay contacts have opened or that there is an open in the POWER-to-PUMP circuit from the IRCM pin No. 5 to the FPM splice. Start engine and listen for fuel pump stopping, stall or stumble while performing "WIGGLE" test on pump power circuit from IRCM. Inspect harness and connectors with key off. If a fault is found, isolate and repair, clear codes and retest. If no fault is found, problem cannot be duplicated at this time. Clear codes for future testing sequence.
69. Continuous Memory Code 83 or 87: Checking EEC-IV Harness. A Continuous Memory Code 83 or 87 indicates that during vehicle operation there has been an open condition in the VPWR circuit of the IRCM, an open coil in the fuel pump relay, or an open in the fuel pump primary circuit. Start engine and listen for fuel pump stopping, stall or stumble while performing "WIGGLE" test on EEC-IV harness fuel pump circuit (pin No. 22 or 41) between the ECA and IRCM (pin No. 18 or 11). Inspect harness and connectors with key off. If a fault is found, isolate and repair, clear codes and retest. If no fault is found, problem cannot be duplicated at this time. Clear codes for future testing sequence.

D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS

This test should be performed ONLY if a problem has been detected in transaxle. If any of these service codes appeared during SELF-TEST, the AXOD DRIVE CYCLE TEST should be performed. A jumper harness is used to connect to the transmission bulkhead connector and test electrical circuits. The following AXOD transaxle related items have malfunctioned or failed as indicated

1. Code 39: Transaxle converter by-pass clutch is not operating properly.
2. Code 59, 62, 68 and 69: Refer to «D21 - AXOD TRANSAXLE»(/ford/mustang/iii-1986-1993/remont/testing-diagnostics/#23l-cec-tests-wcodes__d21-axod-transaxle) for summary of these codes.
3. Code 89: Transaxle converter by-pass clutch solenoid has stayed always open or closed.

The following service codes are not AXOD transaxle related, but can affect converter clutch by-pass operation. Service these components before servicing AXOD transaxle codes

1. Code 21: Engine Coolant Temperature (ECT) sensor out of range.
2. Code 22: Manifold Absolute Pressure (MAP) sensor out of range.
3. Code 23: Throttle Position Sensor (TPS) out of range.
4. Code 24: Air Charge Temperature (ACT) sensor out of range.
5. Code 29: Vehicle Speed Sensor (VSS) not functioning.
6. Code 74: Brake ON/OFF (BOO) switch always open or brake not applied during KOER SELF-TEST.
7. Code 75: Brake ON/OFF (BOO) switch always closed.

The following service code indicates that a transaxle component may have caused faulty engine idle speed control

Scheme 138

Scheme 139

1. Code 57: Neutral Pressure Switch (NPS) failed in Neutral (open) position. The NPS is normally open and closes with hydraulic pressure. Failure of transaxle to engage in "D" or "R" will cause Code 57 to be displayed. Check for proper hydraulic pressure before testing AXOD transaxle electrical components.
2. Code 67: Neutral Pressure Switch (NPS) failed closed. NOTE: Ensure that all components are connected before performing test. Perform AXOD DRIVE CYCLE TEST on a slight upgrade or flat terrain. If any other non-AXOD related codes appear, service those codes first as they could affect electrical operation of transaxle. NOTE: All components must be connected for this test and the following AXOD DRIVE CYCLE TEST must be performed
3. Record and clear Continuous Memory Codes.
4. Warm engine to operating temperature.
5. With transaxle in "D" range, lightly accelerate from a stop to 40 MPH to allow transaxle to shift into 3rd gear. Hold speed and throttle opening steady for a minimum of 15 seconds (30 seconds above 4000 feet altitude).
6. Shift transaxle into overdrive and accelerate lightly from 40 to 50 MPH to allow transaxle to shift into 4th gear. Hold speed and throttle opening steady, in 4th gear, for a minimum of 15 seconds.
7. With transaxle in 4th gear, throttle open and speed steady, lightly apply and release brakes (enough to turn on brake lights). Hold speed and throttle opening steady for an additional 15 seconds.
8. Brake to a stop and remain stopped for a minimum of 20 seconds with transaxle in overdrive range. Perform KOEO SELF-TEST and record Continuous Memory Codes. (Scheme 138): Jumper Harness (Scheme 139): Transmission Component Locations

1. Continuous Memory Code 39: Faulty Converter By-Pass Clutch (CBC), Check Harness Connections. Check that vehicle harness connector is fully attached to transaxle bulkhead connector and that vehicle harness connector terminals are fully seated in connector. If connector or terminals are not okay, repair as required and repeat QUICK TEST. If connector and terminals are okay, go to next step.
2. Checking Solenoid Resistance. Install jumper harness to transaxle bulkhead connector. Connect VOM positive test lead to Red wire and negative test lead to Black wire. Check resistance. If reading is between 20 and 40 ohms, go to QUICK TEST and service codes as required. If reading is not between 20 and 40 ohms, go to next step.
3. Check By-Pass Clutch Application. Connect jumper harness Red wire to battery positive post. With engine running and transaxle in 3rd gear, connect jumper harness Black wire to ground (to energize by-pass clutch solenoid). DO NOT connect with polarity reversed, otherwise solenoid diode will be damaged. If by-pass clutch is applied (engine RPM drops slightly), there is no electrical component failure. By-pass clutch is operating properly. Error code may be indicating a slipping by-pass clutch. Service transaxle for a no converter clutch apply condition and repeat QUICK TEST. If by-pass clutch is not applied (engine RPM does not drop), go to next step.
4. Check By-Pass Solenoid Valve. Check main control by-pass clutch control valve (in valve body) for sticking. If valve is sticking, service spool valve as necessary. If valve is okay, go to next step.
5. Check By-Pass Solenoid. Remove by-pass solenoid. Check condition of "O" ring. Also check for contamination in/on solenoid or small hole in valve. Shake solenoid vigorously to check for free armature. If solenoid is faulty, replace by-pass clutch solenoid and repeat QUICK TEST. If solenoid is okay, service transaxle for a no converter clutch apply condition and repeat QUICK TEST. NOTE: The THS 4/3 and 3/2 pressure switches are normally open and close with hydraulic pressure. Failure of transaxle to engage in "D" will cause Code 59 to be displayed. Failure of transaxle to shift into 3rd gear will cause Code 69 to be displayed. Check for proper hydraulic operation before testing electrical components.
6. Code 59: THS 4/3 Switch Failed to Open, Check Wiring. Check that vehicle harness connector is fully engaged in transaxle bulkhead connector and that vehicle harness connector terminals are fully seated in connector. If connector or terminals are not okay, repair as required and repeat QUICK TEST. If connector and terminals are okay, go to next step.
7. Check Switch For Continuity. Install jumper harness to transaxle bulkhead connector. Using VOM, check for continuity between engine ground and Blue wire. With engine running and transaxle in Neutral, VOM should indicate no continuity (infinite resistance). Shift transaxle into "D". Switch should close and resistance should be less than 10 ohms. Switch should stay closed in 1st, 2nd and 3rd gears, and then open in 4th gear. If circuit is okay, go to QUICK TEST and service codes as required. If circuit is not okay, go to next step.
8. Checking Internal Connections. Remove transaxle side oil pan. Check that internal connector with Blue wire is firmly attached to THS 4/3 pressure switch. Connector should not pull off easily or fit loosely. If connector is not okay, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If connector is okay, go to next step.
9. Check Internal Wiring. Remove connector from pressure switch by pushing on end of connector, while pulling on wire end of connector. Check for continuity in bulkhead connector by measuring resistance between Blue wire and terminal inside connector just removed. If reading is more than 2 ohms, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If reading is less than 2 ohms, go to next step.
10. Check THS 4/3 Switch. Remove THS 4/3 pressure switch. Install a 1/8-27 pipe fitting that can be connected to LOW pressure air supply in order to pressure test leaks and switch closure. With 50 psi (3.5 kg/cm 2 ) applied, check for ruptured diaphragm by submerging switch in clean transmission fluid. NEVER check in water. Check for bubbles coming out of small vent hole near switch terminal. If bubbles show, diaphragm has failed. Replace THS 4/3 pressure switch and repeat QUICK TEST. If no bubbles show, go to next step.
11. Check Switch Resistance. With 50 psi (3.5 kg/cm 2 ) applied to switch, check resistance between switch terminal and switch case. If reading is less than 8 ohms, hydraulic pressure circuit to switch may have excessive leaks. Service transaxle as required. If reading is more than 8 ohms, replace switch. Repeat step 8), and then QUICK TEST. Codes 39, 59, 62, 69 and 89 should no longer be displayed. NOTE: If Code 62 appears in KOEO SELF-TEST, THS 3/2 circuit has failed. If Code 62 appears in KOER SELF-TEST, THS 4/3 circuit has failed. If Code 62 appears in both SELF-TESTS, follow entire test procedure to determine which circuit has failed.
12. Code 62. Remove vehicle harness connector from transaxle bulkhead connector and install jumper harness. Using DVOM, measure continuity between engine ground and White wire (THS 3/2 circuit). With engine off, DVOM should indicate no continuity (infinite resistance). Measure continuity between engine ground and Blue wire (THS 4/3 circuit). With engine running and transaxle in Neutral, VOM should indicate no continuity (infinite resistance). If all readings show no continuity, go to QUICK TEST and service codes as required. If any reading indicates continuity, go to next step.
13. Check Internal Wiring. Remove transaxle side oil pan. Check for pinched, cut, or otherwise grounded wiring. If wiring is damaged, replace bulkhead connector and wiring assembly. After repairs, repeat QUICK TEST. If THS 4/3 pressure switch wiring is okay, go to step 15). If THS 3/2 pressure switch wiring is okay, go to next step.
14. Checking 3/2 Switch. Remove wiring from THS 3/2 pressure switch. Using DVOM, check pressure switch for continuity to engine ground by connecting one lead to switch terminal and other lead to valve body. If there is no continuity (infinite resistance), go to step 16). If there is continuity to ground, replace THS 3/2 pressure switch and repeat QUICK TEST.
15. Check 4/3 Switch. Remove wiring from THS 4/3 pressure switch. Using DVOM, check pressure switch for continuity to engine ground by connecting one lead to switch terminal and other lead to valve body. If there is continuity to ground, replace 4/3 pressure switch and repeat QUICK TEST. If there is no continuity (infinite resistance), go to next step.
16. Check Internal Wires. Using DVOM and with wiring removed from both pressure switches, check continuity to ground. Connect one test lead to White wire and other test lead to ground. Connect one test lead to Blue wire and other test lead to ground. Ensure internal terminals are not touching any metallic parts. If there is continuity to ground, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If there is no continuity (infinite resistance), go to QUICK TEST and service codes as required. NOTE: The THS 4/3 and 3/2 pressure switches are normally open switches that close with hydraulic pressure. Failure of transaxle to engage in "D" will cause service Code 59 to be displayed. Failure of transaxle to shift into 3rd gear will cause Code 69 to be displayed. Check for proper hydraulic operation before testing electrical components.
17. Code 69: Check Wiring. Check that vehicle harness connector is fully attached to transaxle bulkhead connector and that terminals are fully seated in connector. If connector or terminals are faulty, repair as required and repeat QUICK TEST. If connector and terminals are okay, go to next step.
18. Check Switch For Continuity. Install jumper harness to transaxle bulkhead connector. Using DVOM, check for continuity between engine ground and White wire. With engine running and transaxle in Drive, 1st gear, or 2nd gear, VOM should indicate no continuity (infinite resistance). When transaxle shifts into 3rd or 4th gear, the switch should close and resistance should be less than 10 ohms between White wire and engine ground. If circuit is okay, go to QUICK TEST and service codes as required. If circuit is not okay, go to next step.
19. Checking Internal Connections. Remove transaxle side oil pan. Check that internal connector with White wire is firmly attached to THS 3/2 pressure switch. Connector should not pull off easily or fit loosely. If connector is faulty, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If connector is okay, go to next step.
20. Check Internal Wiring. Remove connector from pressure switch by pushing on end of connector, while pulling on wire end of connector. Check for continuity in bulkhead connector by measuring resistance between White wire and terminal inside connector just removed. If reading is more than 2 ohms, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If reading is less than 2 ohms, go to next step.
21. Check THS 2/3 Switch. Remove THS 3/2 pressure switch. Install a 1/8-27 pipe fitting that can be connected to LOW pressure air supply in order to pressure leak and test switch closure. With 50 psi (3.5 kg/cm 2 ) applied, check for ruptured diaphragm by submerging switch in clean transmission fluid. NEVER use water to test switch. Check for bubbles coming out of small vent hole near switch terminal. If bubbles show, diaphragm has failed. Replace THS 3/2 pressure switch and repeat QUICK TEST. If no bubbles show, go to next step.
22. Check Switch Resistance. With 50 psi (3.5 kg/cm 2 ) applied to switch, check resistance between switch terminal and switch case. If reading is less than 8 ohms, hydraulic pressure circuit to switch may have excessive leaks. Service transaxle as required. If reading is more than 8 ohms, replace switch. Repeat steps 21) and 22), and then repeat QUICK TEST. Codes 39, 59, 62, 69 and 89 should no longer be displayed.
23. Code 89: LUS Circuit Failed. If Code 39 is also displayed, go to CIRCUIT TEST for that code. Check that vehicle harness connector is fully attached to transaxle bulkhead connector and that vehicle harness terminals are fully seated in connector. If connector or terminals are not okay, repair as required and repeat QUICK TEST. If connector and terminals are okay, go to next step.
24. Check Solenoid Resistance. Install jumper harness to transaxle bulkhead connector. Connect DVOM positive test lead to Red wire and negative test lead to Black wire. Check resistance. If reading is between 20 and 40 ohms, switch is okay, go to QUICK TEST and service codes as required. If reading is not between 20 and 40 ohms, go to next step.
25. Check Internal Connections. Remove transaxle side oil pan. Check that internal connector is fully attached to solenoid. If connector is okay, go to next step. If connector is not okay, fully engage connector and check continuity once more. If resistance is still not between 20 and 40 ohms, go to next step. If resistance is now okay, repeat QUICK TEST.
26. Check Solenoid Continuity. Remove connector from solenoid by pulling on wires at 2-way connector. Check solenoid continuity by connecting DVOM positive test lead to solenoid positive terminal and negative test lead to solenoid negative terminal (polarity symbols, + and -, are stamped on solenoid frame). If circuit is open (infinite resistance), replace solenoid and then repeat QUICK TEST. If solenoid is okay (20 to 40 ohms resistance), replace bulkhead connector and wiring assembly. Connect all internal connectors and repeat step 24). If circuit tests okay, install oil pan. Repeat KOEO SELF-TEST. Code 89 should no longer be displayed. NOTE: The NPS is normally open and closes with hydraulic pressure. Failure of transaxle to engage in "D" or "R" will cause Code 57 to be displayed. Check for correct hydraulic pressure before testing electrical components.
27. Code 57: NPS Failed Open, Check Wiring. Check that vehicle harness connector is fully attached to transaxle connector and that vehicle harness terminals are fully seated in connector. If connector or terminals are not okay, repair as required and repeat QUICK TEST. If connector and terminals are okay, go to next step.
28. Check Switch For Continuity. Install jumper harness to transaxle bulkhead connector. Using DVOM, check continuity between Green wire and engine ground. With engine running and transaxle in "P" or "N", DVOM should indicate no continuity (infinite resistance). Shift transaxle into "R" and "D" ranges, switch should close. Resistance should be less than 10 ohms in both ranges. If circuit is okay, go to QUICK TEST and service codes as required. If circuit is not okay, go to next step.
29. Check Internal Connections. Remove transaxle side oil pan. Check that terminal connector with Green wire is firmly attached to NPS. Connector should not pull off easily or fit loosely. If connector is not okay, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If connector is okay, go to next step.
30. Check Internal Wiring. Remove connector from NPS by pushing on end of connector while pulling on connector wire. Check for continuity in bulkhead connector by measuring resistance between service connector Green wire and terminal inside connector just removed. If resistance is greater than 2 ohms, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If reading is less than 2 ohms, go to next step.
31. Check THS NPS Switch. Remove NPS. Install a 1/8-27 pipe fitting that can be connected to LOW pressure air supply in order to pressure leak and test switch closure. With 50 psi (3.5 kg/cm 2 ) applied, check for ruptured diaphragm by submerging switch in clean transmission fluid. NEVER use water to test switch. Check for bubbles coming out of small vent hole near switch terminal. If bubbles show, diaphragm has failed. Replace NPS and repeat QUICK TEST. If no bubbles show, go to next step.
32. Check Switch Resistance. With 50 psi (3.5 kg/cm 2 ) applied to switch, check resistance between switch terminal and switch case. If reading is 8 ohms or less, hydraulic pressure circuit to switch may have excessive leaks. Service transaxle as required. If reading is more than 8 ohms, replace switch. Repeat step 28), and then repeat QUICK TEST. Codes 39, 59, 62, 69 and 89 should no longer be displayed. NOTE: The Transmission Temperature Switch (TTS) is a normally closed switch that opens when transmission oil temperature reaches 270°F (132°C). Perform the following test ONLY on a cool transmission. If the circuit has failed open, the ECA assumes the transmission is hot and applies the converter clutch more frequently to allow the transmission to cool.
33. Check Wiring. Check that vehicle harness connector is fully attached to transaxle connector and that vehicle harness terminals are fully seated in connector. If connector or terminals are not okay, repair as required and repeat QUICK TEST. If connector and terminals are okay, go to next step.
34. Check Bulkhead Connector. Ensure that the correct bulkhead connector has been installed. The connector should be "Natural" color and have 6 pin terminals. If connector is incorrect, replace connector. If connector is correct, go to next step.
35. Check Switch Circuit Continuity. Install jumper harness on transmission bulkhead connector. Using a DVOM, check continuity between engine ground and Yellow wire. Since the TTS is a normally closed switch, the circuit should be closed when the transmission temperature is less than 270°F (132°C). Resistance should be less than 10 ohms between the Yellow wire and ground. If circuit is okay, go to QUICK TEST procedures and service other codes. If circuit is faulty, go to next step.
36. Check Internal Connectors. Remove transaxle side oil pan. Check that terminal connector with Yellow wire is firmly attached to TTS. Connector should not pull off easily or fit loosely. If connector is faulty, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If connector is okay, go to next step.
37. Check Internal Wiring. Remove connector from TTS by pushing on end of connector while pulling on connector wire. Check for continuity in bulkhead connector by measuring resistance between service connector Green wire and terminal inside connector just removed. If resistance is greater than 2 ohms, replace bulkhead connector and wiring assembly. Repeat QUICK TEST. If reading is less than 2 ohms, go to next step.
38. Check Temperature Switch. Disconnect internal connector from switch. Check for continuity between engine ground and "Nail Head" connecting pin on the switch. Resistance should be less than 8 ohms. Ensure switch terminal is not loose or an intermittent open circuit may result. If resistance and switch test okay, testing is complete. If switch is faulty, replace switch, reconnect internal wiring and verify continuity to ground.
39. Neutral Pressure Switch (NPS) Failed Closed, Check Wiring. Remove vehicle harness connector from transaxle bulkhead connector and install jumper harness. Check continuity between engine ground and Green wire (NPS circuit). With engine off, resistance should be infinite. If resistance is infinite, switch has not failed in closed position. Service other codes as required. If there is continuity between the Green wire and ground, go to next step.
40. Check Internal Wiring. Remove oil pan and check for pinched, cut or otherwise grounded wiring. If wiring is faulty, replace transaxle bulkhead connector. Repeat QUICK TEST. If wiring is okay, go to next step.
41. Check NPS Switch. Remove wiring from NPS. Measure the pressure switch for continuity to engine ground. Connect one test lead to switch connector and other to engine ground. If resistance is infinite, switch is open, go to next step. If there is continuity to ground, replace NPS and repeat QUICK TEST.
42. Check Internal Wires. Remove wire from NPS and check continuity to ground. Connect one test lead to Green wire and other lead to ground. Ensure internal terminals are not shorted to ground. If there is continuity to ground, replace bulkhead connector and repeat QUICK TEST. If there is infinite resistance, repeat QUICK TEST and service codes as required.

2.3L MPFI EEC-IV Wiring Diagram (Mustang). Scheme 140

2.3L HSC & HSO MPFI EEC-IV Wiring Diagram (Tempo & Topaz). Scheme 141

See also:
• IGNITION SYSTEM - TFI-IV
• EQUIPMENT HOOK-UP
• VISUAL CHECK & VEHICLE PREPARATION
• D19 - SYSTEM CHECK
• COMPUTED TIMING CHECK
• D15 - CODE 15 KOEO CONTINUOUS
• DIAGNOSIS BY SYMPTOM
• D14 - NO CODES/CODES NOT LISTED
• D13 - SPARK TIMING CHECK
• DYNAMIC RESPONSE OR WIDE OPEN THROTTLE (WOT) CHECK
• ENGINE ID CODES
• FAILURE MODE EFFECTS MANAGEMENT (FMEM), CODE 98
• CONTINUOUS MONITOR MODE (WIGGLE TEST)
• SYMPTOM/TEST MENU
• D17
• B5
• B6
• B8
• B2
• B1
• B9
• B4
• B10
• B13
• D4
• C2
• D22
• D5
• B7
• D1
• C1
• B15
• B14
• D10
• D12
• D11
• A2 - VEHICLE BATTERY
• A3 - REFERENCE VOLTAGE
• D20 - INTAKE AIR CONTROL VALVE (IAC)
• D16 - OUTPUT STATE CHECK NOT FUNCTIONING
• D24 - AXOD ELECTRICAL SYSTEM DIAGNOSIS
• D21 - AXOD TRANSAXLE