Engine Controls - Tests W/codes Mazda Navajo I

INTRODUCTION

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with self-diagnostics. If no fault codes or only pass codes are present after entering self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).

DIAGNOSTIC FORMATS

Use 2 diagnostic formats to test and service EEC-IV system: QUICK TEST and CIRCUIT TESTS. QUICK TEST allows technician to identify problems and retrieve and record service codes. TESTS check circuits, sensors and actuators.

Before starting any CIRCUIT TEST (TEST), follow all steps under QUICK TEST to find correct CIRCUIT TEST (TEST). If vehicle passes QUICK TEST and no driveability symptoms or intermittent faults exist, EEC-IV system is okay. Problem is in another system.

SERVICE CODES

These 3 types of service codes can be retrieved during self-test procedure: Key On Engine Off (KOEO), Key On Engine Running (KOER) and Continuous Memory. (Scheme 9) See QUICK TEST for self-test procedures. Codes may be cleared from Electronic Control Assembly (ECA) memory by technician after they have been recorded or repaired. See CLEARING CODES.

KOEO & KOER Codes (Hard Faults) - These codes indicate faults are present at time of testing. A hard fault may cause CHECK ENGINE light to glow and remain on until fault is repaired. If KOEO or KOER codes are retrieved during KOEO SELF-TEST or KOER SELF-TEST, use KOEO SELF-TEST CODE REFERENCE table or KOER SELF-TEST CODE REFERENCE table to select correct CIRCUIT TEST (TEST) for testing and repair.

Continuous Memory Codes (Soft Faults) - Continuous Memory Codes are retrieved during KOEO SELF-TEST. These codes may cause CHECK ENGINE light to flicker or glow. Light will go out after fault goes away. These faults indicate a defect that may or may not be present at time of testing; however, corresponding trouble code will be retained in ECA memory.

If fault does not reoccur within 40 warm-up cycles, code will be erased from ECA memory. Continuous memory failures may be caused by sensor, connector or wiring problems. See INTERMITTENTS in TESTS W/O CODES article.

RETRIEVING CODES

Service codes are retrieved from EEC-IV system through self-test connector. Various methods and test equipment may be used to access these codes.

1. Analog Volt-Ohmmeter (VOM)
2. In-Dash CHECK ENGINE Light
3. Scan Tester
4. SUPER STAR II Tester

KOEO & KOER Self-Test Codes

All service codes are 2- or 3-digit numbers. Codes are outputted, one digit at a time, by ECA. These codes indicate current faults in system and should be serviced in order of appearance. See KOEO SELF-TEST CODE REFERENCE or KOER SELF-TEST CODE REFERENCE tables to find correct CIRCUIT TEST (TEST).

Codes are shown as voltage pulses. If using CHECK ENGINE light, service codes are displayed as light pulses. If using Volt-Ohmmeter (VOM), service codes are displayed as the needle sweeps. (Scheme 9)

Pay careful attention to length of pauses in order to read codes correctly. A 1/2-second pause occurs between number of sweeps in a digit and a 2-second pause occurs between digits in a code. A 4-second pause occurs between each code. KOEO codes are separated from Continuous Memory Codes by a 6-second delay, a single 1/2-second sweep (Separator) and another 6-second delay. Record codes in order received.

Scan tester, if used, will count pulses and display them as a digital code. STAR Series Tester will add a zero (0) to single-digit Separator Code (10) and Dynamic Response Code (10). Dynamic Response Code is displayed in KOER SELF-TEST. (Scheme 9)

Separator Pulse

Single 1/2-second separator pulse is issued 6-9 seconds after last KOEO code. Continuous Memory Codes (soft faults) are displayed 6-9 seconds after 1/2-second separator pulse. Some digital test equipment may display separator code as a 10 or 1.

Pass Codes

A Code 11 or 111 indicates no service codes are recorded and system passes that portion of test. If Code 11 or 111 is not received in KOEO SELF-TEST, codes received during KOER SELF-TEST may not be valid. Code 11 or 111 (pass code) must be observed in KOEO SELF-TEST. A Code 111-1-111 output during KOEO SELF-TEST indicates no KOEO codes or Continuous Memory Codes are recorded.

Continuous Memory Codes

These codes result from information stored by ECA during continuous self-test monitoring. Codes are displayed in KOEO SELF-TEST after separator pulse code. Use these codes for diagnosis ONLY when KOEO SELF-TEST and KOER SELF-TEST result in Code 11 or 111 (pass code) and all steps under QUICK TEST are successfully completed. These codes indicate faults recorded within last 40 engine starts. Fault may or may not be currently present. See CONTINUOUS MEMORY CODE REFERENCE table for definitions of codes.

Fast Codes

At start of KOEO SELF-TEST and after Wide Open Throttle (WOT) request in KOER SELF-TEST, ECA outputs short bursts of information, known as Fast Codes, used by manufacturer during assembly. With most equipment, these code bursts are not visible as entire code sequence lasts less than 1/2 second. If this fluctuation is visible on test equipment, ignore it.

Scheme 9

CLEARING CODES

Note. DO NOT disconnect vehicle battery to clear codes. This will erase stored operating information from Keep-Alive Memory (KAM). If KAM has been cleared, drive vehicle 10 miles or more to allow ECA to relearn operating conditions and driving style of vehicle. Driveability may be affected during relearning cycle.

To clear codes from ECA memory, start KOEO SELF-TEST. When service codes appear on test equipment or CHECK ENGINE light, disconnect jumper wire from Self-Test Input (STI) connector. If using SUPER STAR II Tester, Unlatch center button. This procedure erases Continuous Memory Codes from ECA memory. If problem has not been corrected and fault is still present, hard code will be reset in ECA memory.

Description

Following procedures are functional tests of EEC-IV system. These 7 basic test steps must be carefully followed in sequence, otherwise misdiagnosis or replacement of non-faulty components may result.

1. Visual Check & Vehicle Preparation
2. Equipment Hookup
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. Intermittents & Diagnosis By Symptom

Diagnostic Aids

After all tests, servicing or repairs have been completed, repeat QUICK TEST procedure to ensure all EEC-IV systems work properly and service codes are no longer present.

VISUAL CHECK & VEHICLE PREPARATION

Complete all steps in BASIC TESTING article before proceeding to next test step. Ensure vacuum hoses are connected correctly and EEC-IV wiring harnesses are connected.

EQUIPMENT HOOKUP

Apply parking brake. Place shift lever in Park (A/T) or Neutral (M/T). Block drive wheels. Turn off all electrical loads. Connect appropriate test equipment to vehicle as follows

Note. Accuracy of service codes depends on correct operation of non-EEC-IV components and systems. All non-EEC problems in engine must be corrected before trying to diagnose EEC-IV system.

Perform KOEO SELF-TEST and KOER SELF-TEST with analog Volt-Ohmmeter (VOM), CHECK ENGINE light, SUPER STAR II tester or appropriate scan tester. After codes have been retrieved, use KOEO SELF-TEST CODE REFERENCE or KOER SELF-TEST CODE REFERENCE tables to select correct CIRCUIT TEST (TEST) for testing and repair.

Analog Volt-Ohmmeter (VOM)

1) Turn ignition off. Set VOM at0-15 volt DC range. Connect positive lead of VOM to positive battery terminal.

2) Connect negative VOM lead to Self-Test Output (STO) terminal of self-test connector. Self-test connector is located at right front inner fender panel. (Scheme 10) Connect jumper wire from Self-Test Input (STI) pigtail to signal return terminal of self-test connector. KOEO SELF-TEST will activate when ignition is turned on.

3) Turn ignition on, and observe voltmeter. Codes are shown as voltage pulses (needle sweeps). (Scheme 9) Pay careful attention to length of pauses in order to read codes correctly. A 1/2-second pause occurs between number of sweeps in a digit and a 2-second pause occurs between digits in a code.

4) A 4-second pause occurs between each code. KOEO codes are separated from Continuous Memory codes by a 6-9 second delay, a single 1/2-second sweep (Separator) and another 6-9 second delay. Record codes in order received.

Note. If no code is present and engine will not start, go to the BASIC TESTING article.

5) Record all codes displayed, and repair fault as necessary. Refer to KOEO SELF-TEST CODE REFERENCE table to determine correct CIRCUIT TEST (TEST). If no code is present and engine starts, begin KOER SELF-TEST and go to next step.

6) Start engine. Run it at 2000 RPM for 2 minutes to ensure HEGO sensor is operating. Ensure vehicle is at normal operating temperature.

7) Observe voltmeter. Record sweeps to determine KOER codes stored. (Scheme 9) Use KOER SELF-TEST CODE REFERENCE table to determine appropriate CIRCUIT TEST (TEST).

CHECK ENGINE Light

1) Connect jumper wire from Self-Test Input (STI) pigtail to signal return terminal of self-test connector. (Scheme 10) KOEO SELF-TEST will activate when ignition is turned on. Turn ignition on, and observe CHECK ENGINE light. Record pulses (light flashes) to determine KOEO codes stored. (Scheme 9)

Note. Reading code from CHECK ENGINE light pulses is similar to reading code from needle sweep of Analog Volt-Ohmmeter (VOM).

2) If no code is present and engine does not start, go to the BASIC TESTING article. If no code is present and engine starts, begin KOER SELF-TEST and go to next step.

3) Start engine. Run it at 2000 RPM for 2 minutes to ensure HEGO sensor is operating. Ensure vehicle is at normal operating temperature.

4) Observe CHECK ENGINE light. Record pulses to determine KOER codes stored. (Scheme 9) Use KOER SELF-TEST CODE REFERENCE table to determine appropriate CIRCUIT TEST (TEST).

Scan Tester

Follow manufacturer instructions to hook up equipment and record service codes.

SUPER STAR II Tester

1) To initiate KOEO self-test, turn ignition off. Connect color-coded adapter cable leads to SUPER STAR II tester. Connect service adapter cables to vehicle self-test connector.

2) Slide adapter switch to EEC-IV position. Slide mode selector switch to FAST position.

Note. SUPER STAR II tester will only display 3-digit codes in FAST position. Display will be blank if used in SLOW position.

3) Turn SUPER STAR II tester on. Display window should flash 888, indicating display check. When 00 appears in display, tester is ready. Set center button in CIRCUIT TEST (TEST) position. Turn ignition on.

4) After all codes have been received by tester, release center button. Retrieve and record all codes in tester memory. Refer to KOEO SELF-TEST CODE REFERENCE table to determine appropriate CIRCUIT TEST (TEST). If no codes exist and engine starts, begin KOER SELF-TEST and go to next step.

Note. If no code is present and engine does not start, go to BASIC TESTING article.

5) Ensure center button on SUPER STAR II tester is unlatched. Start engine, and run it at 2000 RPM for 2 minutes to ensure HEGO sensor is operating. Ensure vehicle is at normal operating temperature. Turn ignition off. Ensure SUPER STAR II tester is on. Set center button to TEST position.

6) Start engine, and allow it to idle. Engine ID will not be displayed. Dynamic response will appear briefly followed by service codes. Record all codes displayed. Refer to KOER SELF-TEST CODE REFERENCE table to determine appropriate CIRCUIT TEST (TEST).

Scheme 10

KOEO SELF-TEST

1) Start engine, and allow it to idle until it reaches operating temperature. If engine does not start or stalls after starting, continue KOEO SELF-TEST. DO NOT depress throttle.

2) Turn ignition off, and wait 10 seconds. Activate self-test procedure by using a jumper wire or appropriate test equipment. Turn ignition on, leaving engine off. Record all KOEO and Continuous Memory Codes.

3) If a Code 11 or 111 (pass code) is not received in KOEO portion of test, service KOEO codes. See KOEO SELF-TEST CODE REFERENCE table. If ECA will not output codes, go to TEST QA. If service codes are received

1. If CHECK ENGINE light was on when vehicle arrived for service, use recorded Continuous Memory Codes and CIRCUIT TEST listed in «KOEO SELF-TEST CODE REFERENCE»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) table before addressing any other symptoms.
2. Use recorded Continuous Memory Codes and the «KOEO SELF-TEST CODE REFERENCE»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) table.
3. If Continuous Memory Code 45 is retrieved, go to «TEST N»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) , step 15). If Continuous Memory Code 46, 48, 215, 216, 217, 232 or 238 is retrieved during KOEO SELF-TEST, see IGNITION SYSTEM in I - SYS/COMP TESTS - FUEL INJECTION article. If Codes 45, 46, 48, 215, 216, 217, 232 and 238 are not retrieved, go to «TEST S»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) , step 2).
4. If vehicle has a no-start condition, go to «TEST AA»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes__test-aa-no-start-edis-ignition) .
5. If vehicle displays a Code 11 or 111 (pass code) and does not have any symptoms described in previous steps, go to «COMPUTED TIMING CHECK»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes__computed-timing-check) .

KOEO SELF-TEST CODE REFERENCE

COMPUTED TIMING CHECK

Turn ignition off, and wait 10 seconds. Using jumper wire or test equipment, activate KOER SELF-TEST. Start engine, and check

1. If engine starts and stalls, or stalls during self-test, go to TEST S.
2. If Code 98 or 998 is displayed, EEC-IV system is operating in Failure Mode Effects Management (FMEM). Vehicle cannot be diagnosed in KOER SELF-TEST. Rerun KOEO SELF-TEST.
3. Check computed timing after last service code has been displayed. Timing will remain fixed for 2 minutes after last code has been retrieved unless self-test is deactivated.
4. Computed timing at crankshaft should equal base timing (10 degrees BTDC) plus 20 degrees BTDC. This timing may vary 3 degrees. If computed timing is within specification, perform KOER SELF-TEST. If timing is not within specification, go to TEST P, step 2).

KOER SELF-TEST

1) DO NOT enter this test sequence until a Code 11 or 111 (pass code) has been retrieved in KOEO SELF-TEST. If system has not passed KOEO SELF-TEST, code recorded in KOER SELF-TEST may not be valid.

2) Deactivate self-test by removing and reconnecting jumper wire, or by procedure specified by test equipment in use. Start engine, and run it for 2 minutes at 2000 RPM to warm-up Heated Exhaust Gas Oxygen (HEGO) sensor. Turn engine off, and wait 10 seconds. Activate KOER SELF-TEST using a jumper wire or appropriate procedure for test equipment used. Start engine. Record all service codes displayed. Check following items

1. If engine starts and stalls, or stalls during self-test, go to «TEST S»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) .
2. If vehicle is equipped with a Brake On-Off (BOO) switch, brake pedal must be depressed and released after ID code portion of test.
3. When Dynamic Response Code appears, perform a brief Wide Open Throttle (WOT). DO NOT perform WOT unless requested.
4. If Code 98 or 998 is displayed, EEC-IV system is operating in Failure Management Effects Mode (FMEM). Vehicle has not passed KOEO SELF-TEST and cannot be diagnosed while in FMEM mode. Rerun KOEO SELF-TEST.
5. If KOER codes are present, refer to appropriate CIRCUIT TEST listed in «KOER SELF-TEST CODE REFERENCE»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If system will not output codes, go to TEST QA.

KOER SELF-TEST CODE REFERENCE

CONTINUOUS MONITOR MODE (WIGGLE TEST)

Continuous Monitor Mode allows technician to attempt a recreation of intermittent fault while monitoring system. This mode, also called wiggle test, may be used in both KOEO SELF-TEST and KOER SELF-TEST. TESTS specify use of this procedure to identify intermittent faults in specific circuits or components.

KOEO Wiggle Test Procedure

1) Connect test equipment. Turn ignition on and activate self-test with jumper lead or diagnostic tester. Wait 10 seconds, and deactivate and then reactivate self-test. Wiggle test mode is now activated. Tap, move and wiggle suspect sensor and/or harness area.

2) If a fault is detected, a service code may be stored in memory and indicated at diagnostic tester or scan tester. If voltmeter is used, needle will sweep. If using CHECK ENGINE light, light will come on. Record code, and perform TEST listed in CONTINUOUS MEMORY CODE REFERENCE table.

KOER Wiggle Test Procedure

1) Connect test equipment. (Scheme 10) Turn ignition off, and wait 10 seconds. Start engine. Activate self-test using jumper lead or diagnostic tester. Wait 10 seconds, and deactivate and then reactivate self-test. DO NOT turn engine off. KOER wiggle test mode is now activated.

2) Tap, move and wiggle suspect 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 tester. If voltmeter is used, needle will sweep. If using CHECK ENGINE light, light will come on. Record code, and perform TEST listed in CONTINUOUS MEMORY CODE REFERENCE .

CONTINUOUS MEMORY CODE REFERENCE

INTERMITTENTS & DIAGNOSIS BY SYMPTOMS

See TESTS W/O CODES article.

ADDITIONAL SYSTEM FUNCTIONS

Additional diagnostic system features are available to help technicians diagnose driveability problems and test EEC-IV systems.

CHECK ENGINE light is intended to alert driver of certain malfunctions in EEC-IV system. Light may also be used to retrieve service codes stored in ECA. When hooked up for KOEO SELF-TEST or KOER SELF-TEST, light will display all codes which turn on light during vehicle operation, not just Continuous Memory Codes.

If light comes on during vehicle operation, vehicle should be inspected as soon as possible. Immediately turning off engine is not necessary. Vehicle can be driven with light on.

If light comes on and then goes off during vehicle operation, code causing light to glow will be stored in ECA memory as a Continuous Memory Code. See CHECK ENGINE LIGHT CODE REFERENCE table.

Light should come on when ignition is turned on and go out when engine is started. If hard fault codes are not present, ECA turns out light when it receives a Profile Ignition Pick-Up (PIP) signal.

CHECK ENGINE LIGHT CODE REFERENCE

Output State Check

Check is used as an aid in servicing output actuators associated with EEC-IV system. It allows technicians to energize and de-energize most system output actuators on command. This mode is entered from KOEO SELF-TEST after all codes have been retrieved. With self-test activated, depress throttle to initiate test sequence. Each time throttle is depressed and released, output actuators will change state (from on to off or off to on).

Failure Mode Effects Management (FMEM), Code 98 Or 998

FMEM mode allows system operation when sensors fail or transmit signals which are out of normal operating range. When this happens, ECA substitutes a mid-range signal for defective sensors while continuing to monitor sensors. If faulty sensor's signals return to normal operating range, ECA will use those signals. A Code 98 or 998 will be displayed when FMEM mode is in effect.

Hardware Limited Operational Strategy (HLOS)

If a number of system or sensor failures are present and ECA is not receiving enough information to operate, ECA will switch to HLOS mode. ECA will output fixed values to allow operation of vehicle. ECA will not output service codes in this mode.

SUMMARY

If no service code (only pass code) is present but driveability problem still exists, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

Note. A breakout box, connected in series with wiring harness and ECA, is necessary to perform most circuit tests. References to test pin numbers found in TEST steps refer to test terminals on manufacturer breakout box. Circuit diagram at beginning of each test identifies circuit and wire colors.

HOW TO USE TESTS

1) Ensure all non-EEC-IV related faults found while performing steps in BASIC TESTING article have been corrected. DO NOT perform any TEST unless instructed by a QUICK TEST procedure. Follow each test step in order until fault is found. When more than one code is retrieved, start with first code displayed.

2) TESTS ensure electrical circuits are okay before sensors or other components are replaced. Always test circuits for continuity between sensor and ECA. Test all circuits for short to power, opens or short to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with ignition on unless otherwise specified in TESTS.

3) DO NOT measure voltage or resistance at ECA. DO NOT connect any test light unless specified in testing procedure. Make all measurements by probing rear of connector. Isolate both ends of circuit and turn ignition off when checking continuity, unless instructed otherwise.

4) Disconnect solenoids and switches from harness before measuring continuity and resistance or applying voltage. After each repair, check all component connections and repeat QUICK TEST .

TEST INDEX

Note. In following tests, circuit diagrams and illustrations are courtesy of Mazda Motors Corp.

TEST AA, NO START (EDIS IGNITION SYSTEM)

Perform this test only when all steps under QUICK TEST have been successfully completed and engine still does not start or when directed here from another test or chart.

This test is only intended to diagnose following EEC-IV ignition systems and circuits.

1. ECA
2. Spark (ECA Controlled)
3. Wiring Harness Circuits (PIP, IGN GND And VPWR)

EDIS Module Circuits. Scheme 11

To prevent replacement of good components, be aware that following non-EEC related areas and components may cause problem.

1. Coil Packs
2. EDIS Module
3. Engine Mechanical Components
4. Fuel Quality And Quantity
5. Ignition (General Condition)
6. Starter And Battery Circuits
7. Variable Reluctance Sensor (VRS)

1) Starting System - Ensure fuel pump inertia switch is closed (button pushed in). Try to start engine. If engine cranks, go to next step. If en gi ne does not crank, check vehicle starting and charging systems.

2) Check VREF Signal At TPS - Turn ignition off, and wait 10 seconds. Set DVOM on 20-volt scale, and disconnect Throttle Position Sensor (TPS). Turn ignition on, leaving engine off. Measure voltage at TPS harness connector between VREF and SIG RTN. (Scheme 11) If reading is 4-6 volts, reconnect TPS and go to next step. If reading is less than 4 volts or greater than 6 volts, go to TEST C.

TPS Harness Connector. Scheme 12

3) Check For Spark At Plugs - Disconnect any spark plug wire, and connect spark tester between plug wire and engine ground. Crank engine, and check for spark. If spark is present and consistent, connect spark plug wire and go to next step. If no spark exists, check ignition system. See BASIC TESTING article.

4) Check Ignition Ground Continuity - Turn ignition off. Wait 10 seconds. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set ohmmeter on 200-ohm scale. Disconnect EDIS module. Measure resistance between pin No. 16 at breakout box and IGN GND circuit at EDIS module vehicle harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

5) Check PIP For Short To Power - Turn ignition off and wait 10 seconds. With breakout box installed, disconnect ECA. Disconnect EDIS module. Set DVOM on 20-volt scale. Measure voltage between test pin No. 56 at breakout box and battery negative post. If voltage is greater than 7 volts, go to next step. If voltage is less than 7 volts, repair short to power. Remove breakout box, reconnect all components and rerun QUICK TEST.

6) Check PIP Circuit Continuity - Turn ignition off. With breakout box installed, disconnect ECA. Disconnect EDIS module. Measure resistance between test pin No. 56 at breakout box and PIP circuit at EDIS module vehicle harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

7) Check PIP Circuit For Shorts To Ground - Turn ignition off. With breakout box installed, disconnect ECA. Disconnect EDIS module. Measure resistance between pin No. 56 (PIP) and pins No. 16, 40, 46 and 60 for short to ground. If all readings are more than 10 k/ohms, go to next step. If any reading is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST. If engine still does not start, go to next step.

8) Isolate Shorts In ECA - Turn ignition off, and wait 10 seconds. With breakout box installed, connect ECA to breakout box. Disconnect EDIS module. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 56 (PIP) and test pins No. 37 and 57 for short to power at breakout box. Measure resistance between test pin No. 56 (PIP) and test pins No. 40 and 60 for short to ground at breakout box. If all resistance readings are between 20 k/ohms and 150 k/ohms, reconnect all components and go to next step. If any resistance reading is less than 20 k/ohms or greater than 150 k/ohms, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST.

9) Check PIP Signal - Turn ignition off. With breakout box installed, disconnect ECA. Reconnect EDIS module. Set DVOM on 20-volt scale. Measure voltage between test pin No. 56 and test pin No. 16 at breakout box. Crank engine and record reading. If voltage is 3-7 volts, go to next step. If voltage is less than 3 volts or greater than 7 volts, go to step 6).

10) Fuel Pump Check - Connect pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning ignition on for one second and observe pressure gauge. Turn ignition off and wait 10 seconds. Repeat sequence 5 times. If pressure increases, go to TEST S. If pressure does not increase, check fuel pump and system for mechanical problems.

Perform this test only when directed by TEST C, TEST J or TEST P. This test is intended to diagnose ECA, EEC power relay, battery voltage and following harness circuits.

1. Ignition Switch
2. KAPWR
3. PWR GND
4. SIG RTN
5. VPWR

Power Relay Circuits. Scheme 13

To prevent replacement of good components, be aware that following non-EEC related areas and components may be cause of problem.

1. Alternator
2. Battery Cables
3. Ground Straps
4. Ignition Switch
5. Voltage Regulator

1) Battery Voltage Check - Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage across battery terminals. If voltage is more than 10.5 volts, go to next step; if it is less than 10.5 volts, service or replace discharged battery.

2) Check Continuity Of PWR GND - Circuit Turn ignition off. Wait 10 seconds. Disconnect and inspect ECA 60-pin connector. With breakout box installed, connect ECA to breakout box. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 40 and 60 at breakout box and negative battery post. If all readings are less than 5 ohms, go to next step. If any reading is more than 5 ohms, repair open in PWR GND circuit. Remove breakout box, reconnect ECA and rerun QUICK TEST .

3) Check For Open Between SIG RTN & PWR GND Circuits At ECA. - Turn ignition off, and wait 10 seconds. With breakout box installed, connect ECA. Set ohmmeter on 200-ohm scale. Measure resistance between test pin No. 46 and test pins No. 40 and 60 at breakout box. If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is greater than 5 ohms, replace ECA. Remove breakout box, and rerun QUICK TEST .

4) Check Continuity Of SIG RTN Circuit - Turn ignition off. Wait 10 seconds. With breakout box installed, connect ECA. Set ohmmeter on 200-ohm scale. Measure resistance between test pin No. 46 at breakout box and SIG RTN circuit at self-test connector. If resistance is less than 5 ohms, remove breakout box, reconnect ECA and go to next step. If resistance is greater than 5 ohms, repair open in SIG RTN circuit. Remove breakout box, reconnect ECA and rerun QUICK TEST.

5) Check KAPWR Circuit Voltage At EEC Power Relay - Turn ignition off. Remove EEC power relay. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between KAPWR circuit at EEC power relay 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, repair open in KAPWR circuit between EEC power relay and battery positive post. Reconnect all components, and rerun QUICK TEST .

6) Check Ignition Circuit Voltage At EEC Power Relay - Turn ignition on, leaving engine off. Remove EEC power relay. Set DVOM on 20-volt scale. Measure voltage between ignition switch circuit at EEC power relay vehicle 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, repair open in ignition switch circuits. Reconnect all components, and rerun QUICK TEST .

7) Check PWR GND Circuit Continuity - Turn ignition off, and wait 10 seconds. Disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between PWR GND circuit at EEC power relay vehicle harness connector and battery negative post. If resistance is less than 10 ohms, go to next step. If resistance is greater than 10 ohms, repair open in circuit. Reconnect ECA, and rerun QUICK TEST .

8) Check Continuity Of VPWR Circuit - Turn ignition off. With breakout box installed, connect ECA. Remove EEC power relay. Measure resistance between pins No. 37 and 57 at breakout box and VPWR circuit at EEC power relay harness connector. If all readings are less than 5 ohms, go to next step. If any reading is more than 5 ohms, repair open in VPWR circuit between EEC power relay and ECA. Remove breakout box, reconnect all components and rerun QUICK TEST .

9) Check VPWR Circuit At EEC Power Relay - Turn ignition off. With breakout box installed, connect ECA. Install EEC power relay. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 37 and 57 and pins No. 40 and 60 at breakout box. If any reading is greater than 10.5 volts, repair open or short to ground in VPWR circuit between ECA and EEC power relay. Remove breakout box, and rerun QUICK TEST . If any reading is less than 10.5 volts, replace EEC power relay. Remove breakout box, and rerun QUICK TEST .

Perform this test if a check for VREF signal has failed in sensor input TESTS DA-DH or if directed by TEST AA or TEST QA . This test is intended to diagnose TPS, PFE and BP sensors, ECA and following harness circuits.

1. SIG RTN
2. VREF

Reference Voltage Circuits. Scheme 14

TEST PIN WIRE COLOR IDENTIFICATION

1) Check Battery Power Circuit - Turn ignition off, and wait 10 seconds. Disconnect and inspect ECA 60-pin connector. With breakout box installed, connect ECA to breakout box. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between test pin No. 37 and SIG RTN/PWR GND circuit of self-test connector. If all voltage readings are greater than 10.5 volts and do not differ by greater than one volt, go to next step. If any reading is less than 10.5 volts or if any reading differs by more than one volt, reconnect sensor (if applicable) and go to TEST B.

2) Check VREF Voltage - Turn ignition on, leaving engine off. With breakout box installed, connect ECA. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is 4-6 volts, go to next step. If voltage is more than 6 volts, go to step 4). If voltage is less than 4 volts, go to step 5).

3) Check VREF & SIG RTN Circuit Continuity - Turn ignition off. If directed here by a sensor test, ensure sensor is disconnected. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 26 at breakout box and VREF circuit at vehicle harness connector of applicable sensor. Measure resistance between test pin No. 46 and SIG RTN circuit at vehicle harness connector of applicable sensor. If all readings are less than 5 ohms, VREF voltage is okay. Remove breakout box, reconnect sensor and rerun QUICK TEST. If any reading is greater than 5 ohms, repair open in VREF or SIG RTN circuit. Remove breakout box, reconnect all components and rerun QUICK TEST .

4) Check For Excess VREF Circuit Voltage - Turn ignition off. Wait 10 seconds. With breakout box installed, disconnect ECA and scan tester or STAR tester (if attached). Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pin No. 26 at breakout box and battery ground. If voltage is less than .5 volt, replace ECA. Remove breakout box, reconnect sensor and rerun QUICK TEST . If voltage is greater than .5 volt, repair short to battery power in vehicle harness. Remove breakout box, reconnect ECA and sensor, and rerun QUICK TEST . Replace ECA if fault still occurs.

5) Check For Shorted TPS Sensor - Turn ignition off, and wait 10 seconds. With breakout box installed, connect ECA. Disconnect Throttle Position Sensor (TPS) from vehicle harness. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is less than 4 volts, go to step 7). If voltage is greater than 4 volts, replace TPS. Remove breakout box, reconnect all components and rerun QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Test skips from step 5) to step 7). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

7) Check For Shorted BP Sensor - Turn ignition off, and wait 10 seconds. With breakout box installed, connect ECA. Disconnect Barometric Pressure (BP) sensor. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is less than 4 volts, turn ignition off. Reconnect BP sensor, and go to step 10). If voltage is greater than 4 volts, replace BP sensor. Remove breakout box, reconnect ECA and sensor, and rerun QUICK TEST .

Note. A break in step numbering sequence at this point. Test skips from step 7) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Check VREF Circuit For Short To Ground - Turn ignition off, and wait 10 seconds. With breakout box installed, disconnect ECA. Disconnect TPS and BP sensor. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 26 and test pins No. 20, 40, 46 and 60 at breakout box. If any resistance reading is less than 5 ohms, repair short to ground. Remove breakout box, connect all components and sensors, and rerun QUICK TEST . If original fault still occurs, replace ECA. If all resistance readings are greater than 5 ohms, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST.

Perform this test only when directed by QUICK TEST. Ambient air temperature must be at least 50°F (10°C) to receive valid input from ACT sensor. Engine coolant temperature must be greater than 50°F (10°C) to pass KOEO SELF-TEST and greater than 180°F (82°C) to pass KOER SELF-TEST. Voltage values in this test are based on a 5-volt VREF signal. Values may vary as much as 15 percent due to sensor and VREF variations.

This test is intended to diagnose following components and circuits.

1. ACT Sensor
2. ECT Sensor
3. ECA
4. Vehicle Harness Circuits (ACT, ECT And SIG RTN)

Temperature Sensor Circuits. Scheme 15

TEST PIN WIRE COLOR IDENTIFICATION

To prevent replacement of good components, be aware that following non-EEC related area may be cause of problem.

1. Air Cleaner Duct
2. Ambient Temperature
3. Coolant Level
4. Cooling System
5. Engine Oil Level
6. Engine Operating Temperature
7. Heat Stove Duct Valve Operation
8. Thermostat
9. Water Pump Drive Belt

1) Code 21/116 Or 24/114: Check Installation & Operation Of Temperature Sensor - Code 21/116 (ECT) or 24/114 (ACT) indicates that corresponding sensor is out of self-test range. Correct range for measurement is 0.3-3.7 volts. Possible causes for this fault are as follows.

1. Ambient Temperature less than 50°F (ACT)
2. Low Coolant Level (ECT)
3. Faulty Harness Connector
4. Faulty Sensor

Start engine, and run it at 2000 RPM for 2 minutes. If vehicle cannot be started, go to step 3). If vehicle stalls or starts then dies, go to TEST S . Ensure upper radiator hose is hot and pressurized. Rerun QUICK TEST . If Code 21, 24, 114 or 116 is present, go to next step. If Code 21, 24, 114 or 116 is not present, service other codes as necessary.

2) Check VREF Circuit Voltage At TPS - Turn ignition off, and wait 10 seconds. Disconnect Throttle Position Sensor (TPS). Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between VREF and SIG RTN circuits at TPS vehicle harness connector. see scheme 8 If voltage is 4-6 volts, reconnect TPS and go to next step. If voltage is less than 4 volts or greater than 6 volts, go to TEST C.

3) Check Temperature Sensor Resistance With Engine Off - Turn ignition off, and wait 10 seconds. Disconnect suspect sensor. Set DVOM on 200-k/ohm scale. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. See ACT & ECT SENSOR SPECIFICATIONS table. If resistance is within specification, perform following step as applicable.

1. For ECT sensor with a no-start condition, go to CIRCUIT TEST AA. DO NOT service Code 21/116 at this time.
2. For all others, go to next step. If resistance is not within specification, replace suspect sensor. Reconnect vehicle harness, and rerun «QUICK TEST»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes) .

ACT & ECT SENSOR SPECIFICATIONS

4) Sensor Resistance Check (Engine Running) - If engine has cooled down, warm engine before measuring sensor resistance. Ensure thermostat is open. Turn ignition off, and wait 10 seconds. Disconnect suspected temperature sensor. Set DVOM on 200-k/ohm scale. Run engine at 2000 RPM for 2 minutes. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. If resistance is within specification, replace ECA. See ACT & ECT SENSOR SPECIFICATIONS table. Reconnect vehicle harness, and rerun QUICK TEST . If resistance is not within specification, replace suspect sensor. Reconnect vehicle harness, and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 4) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 51/118 Or 54/113: Induce Opposite Code (Code 61/117 Or 64/112) - Code 51/118 (ECT) or 54/113 (ACT) indicates that corresponding sensor signal is greater than self-test maximum. Maximum signal voltage for ECT and ACT sensors is 4.6 volts. Possible causes for these faults are as follows.

1. Faulty Connection
2. Faulty ECA
3. Faulty Sensor
4. Open Circuit In Vehicle Harness (ACT Or ECT)

Turn ignition off, and wait 10 seconds. Disconnect suspect temperature sensor. Connect a jumper wire between sensor signal circuit and SIG RTN circuit at temperature sensor vehicle harness connector. Perform KOEO SELF-TEST. See KOEO SELF-TEST under SELF-DIAGNOSTIC SYSTEM. If Code 61, 64, 112 or 117 is not present, remove jumper wire and go to next step. If Code 61, 64, 112 or 117 is present, replace suspect sensor. Remove jumper wire, reconnect vehicle harness and rerun QUICK TEST .

11) Check Continuity Of Sensor Signal & SIG RTN Circuits - Turn ignition off, and wait 10 seconds. Disconnect suspected temperature sensor. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 7 (ECT sensor) or test pin No. 25 (ACT sensor) at breakout box and sensor signal circuit at sensor vehicle harness connector. Measure resistance between test pin No. 46 at breakout box and SIG RTN circuit at sensor vehicle harness connector. If all resistance readings are less than 5 ohms, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST . If any resistance reading is greater than 5 ohms, repair open circuits. Remove breakout box, reconnect all components and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 11) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) Code 61/117 Or 64/112: Induce Opposite Code (Code 51/118Or 54/113) - Code 61/117 (ECT) or 64/112 (ACT) indicates that sensor signal is less than self-test minimum. Minimum signal for ACT and ECT sensor is 0.2 volt. Possible causes for these faults are as follows.

1. Circuit Grounded In Vehicle Harness
2. Faulty Connection
3. Faulty ECA
4. Faulty Sensor

Turn ignition off, and wait 10 seconds. Disconnect vehicle harness connector from suspect sensor. Check for damaged wiring, and repair as necessary. Perform KOEO SELF-TEST. See KOEO SELF-TEST under SELF-DIAGNOSTIC SYSTEM. If Code 51, 54, 113 or 118 is not present, go to next step. If Code 51, 54, 113 or 118 is present, replace suspected sensor. Reconnect vehicle harness, and rerun QUICK TEST .

21) Check VREF Circuit Voltage At TPS - Turn ignition off, and wait 10 seconds. Disconnect suspected temperature sensor. Disconnect Throttle Position Sensor (TPS). Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between VREF and SIG RTN circuits at TPS vehicle harness connector. If voltage is 4-6 volts, reconnect TPS and go to next step. If voltage is less than 4 volts or greater than 6 volts, go to TEST C.

22) Check Temperature Sensor Signal For Shorts To Ground - Turn ignition off, and wait 10 seconds. Disconnect suspected temperature sensor. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 7 (ECT) or test pin No. 25 (ACT) and test pins No. 40, 46 and 60 at breakout box. If any resistance reading is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST . If all resistance readings are greater than 10 k/ohms, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 22) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 51/118, 54/113, 61/117 Or 64/112: Check Sensor - Continuous Memory Codes 51/118 and 54/113 indicate that sensor signal is greater than self-test maximum of 4.6 volts. Code is set during normal driving conditions. Continuous Memory Codes 61/117 and 64/112 indicate that sensor signal is less than self-test minimum of .2 volt. Code is set during normal driving conditions. Possible causes for these faults are

1. Faulty ECA.
2. Faulty sensor.
3. Open or grounded circuit in harness. (Scheme 16)

SENSOR CODES

Sensor Circuit Fault. Scheme 16

Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST). Observe VOM or SUPER STAR II tester for indication of fault while tapping sensor lightly and wiggling sensor connector. If fault is not indicated, go to next step. If fault is indicated, disconnect and inspect connector and terminals. If connector and terminals are okay, replace sensor. Clear continuous memory, and rerun QUICK TEST .

91) Check EEC-IV Vehicle Harness - While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe VOM or SUPER STAR II tester while wiggling and bending EEC-IV harness from sensor to dash panel, a small section at a time. Also check harness from dash panel to ECA. If fault is not indicated, go to next step. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and rerun QUICK TEST .

92) Inspecting ECA & Vehicle Harness Connectors - Turn ignition off, and wait 10 seconds. Disconnect and inspect ECA 60-pin connector. Disconnect suspect sensor connector. Inspect connector and connector terminals for damage. Repair as necessary. If connectors and terminals are okay, clear continuous memory and rerun QUICK TEST. If connectors and terminals are not okay, repair as necessary. Clear continuous memory, and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 92) to step 100). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

100) Continuous Memory Code 338 - Continuous Memory Code 338 indicates engine had not reached normal operating temperature or system is not heating. Cooling system is not properly controlling engine temperature. Following are possible causes for this fault.

1. Head Gasket Leak
2. Heater Hose Leak
3. Thermostat Stuck Open
4. Water Outlet Gasket Leak
5. Water Pump Gasket Leak

Check cooling system for problems.

101) Continuous Memory Code 339 - Continuous Memory Code 339 indicates engine has exceeded high temperature limit. Cooling system is not properly controlling engine temperature. Following are possible causes for this fault.

1. Coolant Leakage
2. Faulty Cooling Fan
3. Faulty Radiator Cap
4. Low Coolant Level
5. Radiator Fins Clogged
6. Thermostat Stuck Closed
7. Water Passages Clogged

Check cooling system for problems.

Perform this test when directed by QUICK TEST. MAF signal voltage is typical for A/T models at normal operating temperature. Voltage signal may vary due to engine load and temperature. Test is intended to diagnose ECA, MAF sensor and following harness circuits

1. VPWR
2. PWR GND
3. MAF
4. MAF RTN

Mass Airflow Sensor (MAF) Circuits. Scheme 17

TEST PIN WIRE COLOR IDENTIFICATION

To prevent replacement of good components, be aware that following non-EEC related areas may be cause of problem.

1. Air Cleaner Element
2. Inlet Air Duct
3. Throttle Body

MAF SIGNAL VOLTAGE

1) Code 26/159: Check VPWR Circuit Voltage - Code 26/159 indicates MAF sensor voltage is out of self-test range. If code is retrieved during KOEO SELF-TEST, voltage exceeds 0.7-volt test range. If Code 26/159 is retrieved during KOER SELF-TEST, voltage is not in 0.2-1.5 volt operating range. Possible causes for this fault are as follows.

1. Faulty ECA
2. Faulty MAF Sensor

Turn ignition off. Disconnect Mass Airflow (MAF) sensor. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between VPWR circuit at MAF sensor vehicle harness connector and negative battery post. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open in VPWR circuit and rerun QUICK TEST .

Note. Code 26/159 may be caused by use of a garage exhaust ventilation system. Ensure vehicle is vented to outside atmosphere before rerunning QUICK TEST .

2) Check MAF Sensor Ground - Turn ignition on, leaving engine off. Disconnect Mass Airflow (MAF) sensor. Set DVOM on 20-volt scale. Measure voltage between VPWR and PWR GND circuits at MAF sensor vehicle harness connector. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open in PWR GND circuit. Reconnect MAF sensor, and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 2) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 66/157 Or 72/129: Check Continuity Of MAF & VPWR Circuits - Code 66/157 indicates that MAF signal was less than .40 volt sometime during last 80 warm-up cycles. Code 72/129 indicates insufficient MAF change during DYNAMIC RESPONSE TEST. See TEST M . Possible causes for these faults are as follows.

1. Air Leak Before Or After MAF Sensor
2. Faulty ECA Or MAF Sensor
3. MAF Circuit Shorted To Ground
4. MAF Sensor Disconnected
5. Open MAF Circuit
6. Open MAF RTN Circuit To MAF Sensor
7. Open PWR GND Circuit To MAF Sensor
8. Open VPWR Circuit To MAF Sensor

Turn ignition off. Disconnect and inspect ECA 60-pin connector. Disconnect Mass Airflow (MAF) sensor. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between VPWR circuit at MAF sensor vehicle harness connector and test pins No. 37 and 57 at breakout box. Measure resistance between MAF circuit at MAF sensor vehicle harness connector and pin No. 14 at breakout box. If all readings are less than 5 ohms, go to next step. If any reading is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST .

11) Check MAF Circuit For Shorts To Ground & MAF RTN Circuit - Turn ignition off. Disconnect Mass Airflow (MAF) sensor. With breakout box installed, disconnect ECA. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 14 and test pins No. 15, 40 and 60 at breakout box. If all resistance readings are greater than 10 k/ohms, go to next step. If any resistance reading is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST .

12) Check Continuity Of PWR GND Circuit - Turn ignition is off. Disconnect Mass Airflow (MAF) sensor. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between PWR GND circuit at MAF sensor vehicle harness connector and battery negative post. If resistance is less than 10 ohms, go to next step. If resistance is greater than 10 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST .

13) Check Continuity Of MAF RTN Circuit - Turn ignition off. Disconnect Mass Airflow (MAF) sensor. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between MAF RTN circuit at MAF sensor vehicle harness connector and test pin No. 15 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

14) Check MAF Signal For Short To Ground - Turn ignition off. Disconnect Mass Airflow (MAF) sensor. With breakout box installed, connect ECA to breakout box. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 14 and test pins No. 15, 40 and 60 at breakout box. If all readings are greater than 10 k/ohms, go to next step. If any readings are less than 10 k/ohms, replace ECA. Remove breakout box, reconnect MAF sensor and rerun QUICK TEST .

15) Check MAF Circuit Output - Turn ignition off. Reconnect Mass Airflow (MAF) sensor. With breakout box installed, connect ECA. Set DVOM on 20-volt scale. Start engine. Measure voltage between test pin No. 14 at breakout box and negative battery post. If voltage is 0.36-1.50 volts, go to next step. If voltage is less than 0.36 volt or greater than 1.50 volts, replace MAF sensor. Remove breakout box, reconnect ECA and rerun QUICK TEST .

16) Turn ignition off. Reconnect Mass Airflow (MAF) sensor. With breakout box installed, connect ECA. Start engine. Measure voltage between test pins No. 14 and 15 at breakout box. If voltage is 0.36-1.50 volts, replace ECA. Remove breakout box, and rerun QUICK TEST. If voltage is less than 0.36 volt or greater than 1.50 volts, replace MAF sensor. Remove breakout box, reconnect ECA and rerun QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Test skips from step 16) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) Code 56/158: Rerun Self-Test With MAF Sensor Disconnected - Code 56/158 indicates MAF sensor signal exceeded 4.5 volts during normal operating temperature or during self-test. Turn ignition off. Disconnect Mass Airflow (MAF) sensor. Start engine and allow to idle for one minute. Turn ignition off. Rerun KOEO SELF-TEST. See KOEO SELF-TEST under SELF-DIAGNOSTIC SYSTEM. If Code 66 or 157 is not present, go to next step. If Code 66 or 157 is present, replace MAF sensor and rerun QUICK TEST.

21) Check MAF Circuit For Short To VPWR - Turn ignition off. Disconnect Mass Airflow (MAF) sensor. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-k/ohm scale. Measure resistance between MAF and VPWR circuits at MAF sensor vehicle harness connector. If resistance is more than 10 k/ohms, replace ECA. Remove breakout box, reconnect MAF sensor and rerun QUICK TEST. If resistance is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

Perform this test only when directed by QUICK TEST or TEST S. Barometric pressure sensor output is digital and must be measured using an oscilloscope or BP tester. Frequency values may vary plus or minus 3 Hz due to sensor variations.

This test is intended to diagnose ECA, BP sensor and following harness circuits.

1. BP SIG
2. SIG RTN
3. VREF

BP Circuits & Tester Hookup. Scheme 18

To prevent replacement of good components, be aware that following non-EEC related areas and components may be cause of problem.

1. Unusually High Or Low Atmosphere Barometric Pressure
2. Basic Engine (Valves, Vacuum Leaks, Timing)

BP SENSOR SPECIFICATIONS

1) Code 22/126: Check For Power To BP Sensor - Code 22/126 indicates BP sensor is out of self-test voltage range. Correct range for measurement is 1.4-1.6 volts. Following are possible causes for this fault.

1. BP Signal Circuit Open Between Sensor And ECA
2. BP Signal Circuit Shorted To VREF, SIG RTN Or Ground
3. Faulty BP Sensor
4. Faulty ECA
5. High Atmospheric Pressure
6. SIG RTN Circuit Open At BP Sensor
7. Vacuum Trapped At BP Sensor
8. VREF Circuit Open At BP Sensor

Turn ignition off. Disconnect Barometric Pressure (BP) sensor from vehicle harness. With BP tester installed, connect tester plugs to DVOM. Set DVOM on 20-volt scale. Turn ignition on. If Red light or no light is on, VREF is either too high or too low. Go to next step. If Green light is on, VREF is okay. Go to step 3).

2) Check For Power At Sensor Vehicle Harness Connector - Turn ignition on. With BP tester installed between vehicle harness connector and BP sensor, connect tester plugs to DVOM. Disconnect Barometric Pressure (BP) sensor. If Green light is on, replace BP sensor and rerun QUICK TEST . If Green light is not on, remove BP tester. Reconnect BP sensor, and go to TEST C.

3) Check BP Sensor Output - With BP tester installed, connect tester plugs to DVOM. Measure BP sensor output voltage. See BP SENSOR VOLTAGE OUTPUT table. If output voltage is within range for altitude in which vehicle is being tested, remove BP tester and go to next step. If output voltage is out of range, remove BP tester and go to step 5).

Note. If possible, measure output voltage of several known good BP sensors on available vehicles. Average voltage will be typical for location on date of testing.

BP SENSOR VOLTAGE OUTPUT

4) Check Continuity Of BP SIG Circuit - Turn ignition off and wait 10 seconds. Disconnect Barometric Pressure (BP) sensor. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance between BP SIG circuit at BP sensor vehicle harness connector and test pin No. 45 at breakout box. If resistance is less than 5 ohms, replace ECA. Remove breakout box, reconnect BP sensor and rerun QUICK TEST . If resistance is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST .

5) Check BP SIG Circuit For Shorts To VREF, SIG RTN & Ground - Turn ignition off and wait 10 seconds. Disconnect Barometric Pressure (BP) sensor. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 45 and test pins No. 26, 40, 46 and 60 at breakout box. If any reading is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect ECA and rerun QUICK TEST . If all readings are greater than 10 k/ohms, replace BP sensor. Remove breakout box, reconnect all components and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 5) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 22/126: Exercise BP Sensor - Continuous Memory Code 22/126 indicates BP sensor was out of self-test range. Correct range for measurement is 1.4-1.6 volts. Code is set during normal driving conditions. Possible causes for this fault are

1. Faulty BP sensor.
2. Faulty BP sensor vehicle harness connectors or terminals. (Scheme 19)
3. Faulty EEC vehicle harness.
4. Unusually high or low barometric pressure.

Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST). Observe VOM or SUPER STAR II tester while performing following

1. Connect a vacuum pump to BP sensor.
2. Slowly apply 25 in. Hg vacuum to BP sensor.
3. Slowly bleed off vacuum from BP sensor.
4. Lightly tap on BP sensor (to simulate road shock).
5. Wiggle BP sensor connector.

If fault is not indicated, go to next step. If fault is indicated, disconnect and inspect connectors and terminals. If connectors and terminals are okay, replace sensor. Clear continuous memory, and rerun QUICK TEST.

Sensor Circuit Fault. Scheme 19

91) Check EEC-IV Vehicle Harness - While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe VOM or SUPER STAR II tester while wiggling and bending EEC-IV harness from sensor to dash panel, a small sections at a time. Also check harness from dash panel to ECA. If fault is not indicated, go to next step. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and rerun QUICK TEST .

92) Check ECA & Vehicle Harness Connectors - Turn ignition off, and wait 10 seconds. Disconnect and inspect ECA 60-pin connector. If connectors and terminals are not okay, repair as necessary. Rerun QUICK TEST . If connectors and terminals are okay, clear continuous memory and rerun QUICK TEST .

Perform this test only when directed by QUICK TEST. Normal range of throttle angle measurement for TPS is 0-85 degrees. To pass QUICK TEST procedure, range of throttle rotation (in degrees) must be within 3 percent of specification. (Scheme 20)

This test is intended to diagnose ECA, TPS and following harness circuits.

1. TPS
2. SIG RTN
3. VREF

To prevent replacement of good components, be aware that following non-EEC related areas may be cause of problem.

1. Binding Throttle Shaft/Linkage Or Cruise Control Linkage
2. Idle Speeds/Throttle Stop Adjustment
3. TPS Not Properly Seated Or Tightened

TPS Specifications Chart. Scheme 20

Note. numbering sequence begins at step 2) . This is due to previous chart references to these testing procedures. No test procedures have been omitted.

2) Code 23/121: Check For Stuck Throttle Plate - Code 23/121 indicates TPS rotational setting may be out of self-test range. Possible causes for this fault are as follows.

1. Binding Throttle Linkage
2. Faulty TPS
3. Faulty ECA
4. TPS Not Properly Seated Or Tightened

Inspect throttle body and linkage for binding and sticking. Ensure linkage is in throttle-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 rerun QUICK TEST. If no mechanical problem is found, go to next step.

3) Code 53/123: Attempt To Generate Code 63/122 - Code 53/123 indicates TPS signal is greater than self-test maximum value. Possible causes for this fault are as follows.

1. Faulty ECA
2. Faulty TPS
3. TPS Not Properly Seated Or Tightened
4. VREF Circuit Shorted In Vehicle Harness

Turn ignition off. Wait 10 seconds. Disconnect and inspect Throttle Position Sensor (TPS). Rerun KOEO SELF-TEST. Ignore all other codes at this time. If Code 63 or 122 exists, go to next step. If Codes 63 and 122 do not exist, go to step 6).

4) Check VREF Circuit Voltage - Turn ignition off, and wait 10 seconds. Disconnect Throttle Position Sensor (TPS). Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between VREF and SIG RTN circuits at TPS vehicle harness connector. If voltage is less than 4 volts or greater than 6 volts, reconnect sensor and go to TEST C. If voltage is 4-6 volts, replace TPS and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 4) to step 6). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

6) Check TPS Circuit For Short To Power - Turn ignition off. Wait 10 seconds. Disconnect Throttle Position Sensor (TPS). Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 47 and test pins No. 26 and 57 at breakout box. If any reading is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST . If all readings are greater than 10 k/ohms, replace ECA. Remove breakout box, reconnect TPS and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 6) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 63/122: Attempt To Generate Code 53/123 Or 23/121 - Code 63/122 indicates TPS signal is less than minimum self-test value. Possible causes for this fault are as follows.

1. Faulty ECA
2. Faulty TPS
3. Open Or Ground Circuit In Vehicle Harness
4. TPS Not Properly Seated Or Tightened

Turn ignition off, and wait 10 seconds. Disconnect and inspect Throttle Position Sensor (TPS). Install jumper wire between VREF and TPS circuits at TPS vehicle harness connector. Perform KOEO SELF-TEST. If no codes are generated, immediately remove jumper wire and go to step 14). Check for Codes 23, 53, 121 or 123 (ignore all other codes at this time). If Codes 23, 53, 121 or 123 are not present, remove jumper wire and go to next step. If Codes 23, 53, 121 or 123 is present, replace TPS. Remove jumper wire, and rerun QUICK TEST.

11) Check VREF Circuit Voltage - Turn ignition off. Wait 10 seconds. Disconnect Throttle Position Sensor (TPS). Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between VREF and SIG RTN circuits at TPS vehicle harness connector. If voltage is 4-6 volts, go to next step. If voltage is less than 4 volts or more than 6 volts, reconnect all components and go to TEST C.

12) Check TPS Circuit Continuity - Turn ignition off, and wait 10 seconds. Disconnect Throttle Position Sensor (TPS). Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-k/ohm scale. Measure resistance between TPS circuit at TPS vehicle harness connector and test pin No. 47 at breakout box. If resistance is less than 5 ohms, go to step 14). If resistance is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Test skips from step 12) to step 14). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

14) Check TPS Circuit For Shorts To Ground - Turn ignition off, and wait 10 seconds. Disconnect Throttle Position Sensor (TPS). Disconnect and inspect ECA 60-pin connector. With breakout box, disconnect ECA. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 47 and test pins No. 40, 46 and 60 at breakout box. If any resistance reading is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST . If all resistance readings are greater than 10 k/ohms, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 14) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) Code 73/167: Dynamic Response (Goose) Test At Wide Open Throttle (WOT) - Code 73/167 indicates TPS did not exceed 25 percent of its rotation during dynamic response check portion of KOER SELF-TEST. A complete WOT must be performed during dynamic response check portion. Run KOER SELF-TEST. Ensure WOT is performed during dynamic response portion of test. If Code 73 or 167 is still present, go to next step. If Code 73 or 167 is not present, system is unable to duplicate Code 73 or 167 at this time. Service any other KOER codes. If no other KOER code is present, testing is complete.

21) Check TPS Movement During Dynamic Response Test - Turn ignition off. Disconnect and inspect ECA 60-pin connector. With breakout box installed, connect ECA to breakout box. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 46 and 47 at breakout box. Rerun KOER SELF-TEST, and ensure a proper WOT is performed. Monitor DVOM voltage during dynamic response check. If voltage increases to greater than 3.5 volts, replace ECA. Remove breakout box, and rerun QUICK TEST . If voltage remains less than 3.5 volts, ensure TPS is properly installed to throttle body. If TPS is properly installed, replace TPS. Rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 21) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 53/123: Monitor TPS Circuit Under Simulated Road Conditions - Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST) . Observe VOM or SUPER STAR II tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position and lightly tap TPS and wiggle harness connector. If fault is indicated, go to next step. If fault is not indicated, go to step 92).

91) Measure TPS Circuit Voltage While Exercising TPS - Turn ignition off. Wait 10 seconds. Disconnect and inspect ECA 60-pin connector. With breakout box installed, connect ECA to breakout box. With VOM or SUPER STAR II tester still connected to STO as in previous step, connect VOM or SUPER STAR II tester between test pins No. 46 and 47 at breakout box. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Observe DVOM, and repeat step 90). If fault occurs at less than 4.25 volts, disconnect and inspect TPS connectors and terminals. If connectors and terminals are okay, replace TPS. Clear continuous memory, and rerun QUICK TEST. If fault does not occur at less than 4.25 volts, TPS over-travel may have caused Code 53/123. If TPS is okay, go to next step.

92) Check EEC-IV Vehicle Harness - While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe VOM or SUPER STAR II tester while wiggling and bending EEC-IV harness from sensor to dash panel, a small section at a time. (Scheme 21) Also check harness from dash panel to ECA. If fault is not indicated, go to next step. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and rerun QUICK TEST.

Sensor Circuit Fault. Scheme 21

93) Check ECA & Harness Connectors - Turn ignition off, and wait 10 seconds. Disconnect and inspect ECA 60-pin connector. If connectors and terminals are okay, clear continuous memory and rerun QUICK TEST . If connectors and terminals are not okay, repair as necessary. Clear continuous memory, and rerun QUICK TEST .

94) Continuous Memory Code 63/122: Monitor TPS Circuit Under Simulated Road Conditions - Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST). Observe VOM or SUPER STAR II tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position, and lightly tap TPS and wiggle harness connector. If fault is not indicated, go to next step. If fault is indicated, disconnect and inspect TPS connectors and terminals. (Scheme 22) If connectors and terminals are okay, replace TPS. Clear continuous memory, and rerun QUICK TEST.

Sensor Circuit Fault. Scheme 22

95) Check EEC-IV Vehicle Harness - While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe VOM or SUPER STAR II tester while wiggling and bending EEC-IV harness from sensor to dash panel, a small section at a time. Also check harness from dash panel to ECA. If fault is not indicated, go to next step. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and rerun QUICK TEST .

96) Check ECA & Harness Connectors - Turn ignition off, and wait 10 seconds. Disconnect and inspect ECA 60-pin connector. If connectors and terminals are okay, clear continuous memory and rerun QUICK TEST. If connectors and terminals are not okay, repair as necessary. Clear continuous memory, and rerun QUICK TEST.

Perform this test when directed by QUICK TEST. This test is intended to diagnose

1. ECA.
2. Vehicle Speed Sensor (VSS).
3. VSS harness circuits.

Vehicle Speed Sensor (VSS) Circuit. Scheme 23

TEST PIN WIRE COLOR IDENTIFICATION

Preliminary Instructions (A/T Models) - Record and clear Continuous Memory Codes. Warm engine to normal operating temperature. In Low gear, accelerate hard to 35 MPH, then coast down to idle and stop. Shut engine off. Perform KOEO SELF-TEST, and record Continuous Memory Codes. Go to step 1).

Preliminary Instructions (M/T Models) - Record and clear Continuous Memory Codes. Warm engine to normal operating temperature. Start in 1st gear, shift to 2nd gear and accelerate moderately to 40 MPH. Coast down to idle and stop. Shut engine off. Perform KOEO SELF-TEST, and record Continuous Memory Codes. Go to step 1).

1) Continuous Memory Code 29/452 - Code 29/452 indicates during last 40 to 80 warm-up cycles, ECA detected fault in VSS output signal. Possible causes for this fault are as follows.

1. Faulty ECA
2. Faulty VSS
3. Open Or Shorted Circuit

Perform appropriate drive cycle procedure. See PRELIMINARY INSTRUCTIONS (A/T MODELS) or PRELIMINARY INSTRUCTIONS(M/T MODELS). If Code 29 or 452 is still present, go to next step. If Code 29 or 452 is not present, clear continuous memory and see INTERMITTENTS in TESTS W/O CODES article.

2) Check VSS Circuit Continuity - Turn ignition off. Disconnect and inspect ECA 60-pin connector. With breakout box installed. disconnect ECA. Disconnect Vehicle Speed Sensor (VSS). Measure resistance between test pin No. 3 at breakout box and VSS DIF (+) circuit at VSS vehicle harness connector. Measure resistance between test pin No. 6 at breakout box and VSS DIF (-) circuit at vehicle harness connector. If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and repeat step 1).

3) Check VSS Circuits For Shorts To Power Or Ground - Turn ignition off. Disconnect Vehicle Speed Sensor (VSS). With breakout box installed, disconnect ECA. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If all resistance readings are greater than 500 ohms, reconnect ECA and go to next step. If any resistance reading is less than 500 ohms, repair short in circuit. Remove breakout box, reconnect all components and repeat step 1).

4) Checking VSS Resistance - Turn ignition off. Disconnect Vehicle Speed Sensor (VSS). Measure resistance across vehicle speed sensor. If resistance is 190-250 ohms, replace ECA. Remove breakout box, reconnect VSS and repeat step 1). If resistance is less than 190 ohms or greater than 250 ohms, replace VSS. Remove breakout box, and repeat step 1).

Perform this test when directed by QUICK TEST. This test is intended to diagnose ECA, Clutch Engage/Interlock Switch, Neutral Drive/Gear Switch and following harness circuits.

1. CES
2. CIS
3. NDS
4. NGS
5. SIG RTN

Neutral Drive Input Circuit. Scheme 24

1) Code 67/522, 525 Or 528: System Identification - Code 67/522, 525 or 528 indicates voltage is high at test pin No. 10 (A/C input) or 30 (neutral drive) while cranking engine during KOEO SELF-TEST. Possible causes for these faults are as follows.

1. A/C Circuit Shorted To Power
2. Clutch Engage/Interlock Switch Circuits Open
3. Faulty ECA
4. Neutral Drive/Gear Switch Circuits Open
5. Starter Relay Disconnected During Self-Test

Note. A break in step numbering sequence occurs at this point. Test skips from step 1) to step 8). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

8) Check Neutral Drive Input - Turn ignition off, and wait 10 seconds. Turn A/C off (if equipped). Place transmission in Neutral or Park. Disconnect and inspect ECA 60-pin connector. With breakout box installed, connect ECA. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pin No. 30 at breakout box and chassis ground. If voltage is greater than one volt, go to next step. If voltage is less than one volt and vehicle is equipped with A/C, go to step 10). If voltage is less than one volt and vehicle is not equipped with A/C, replace ECA.

9) Check Neutral Drive Switch - Turn ignition off, and wait 10 seconds. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Locate and disconnect vehicle harness connector from neutral drive switch. Measure resistance across neutral drive switch. If resistance is greater than 5 ohms, replace neutral drive switch. Remove breakout box, reconnect all components and rerun QUICK TEST. If resistance is less than 5 ohms, repair open in vehicle harness neutral drive switch circuit. Remove breakout box, reconnect all components and rerun QUICK TEST .

10) Check A/C Input - Turn A/C off. If A/C was on, rerun QUICK TEST . If Code 67, 79, 522, 525 or 528 is present, disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pin No. 10 at breakout box and chassis ground. If voltage is greater than one volt, repair short to power in A/C circuit. Remove breakout box, reconnect all components and rerun QUICK TEST . If voltage is less than one volt, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST .

11) Check A/C Input Circuit - Turn A/C on. If engine idles low, ECA is not receiving or recognizing A/C input at test pin No. 10. (Scheme 25) Turn ignition off, and wait 10 seconds. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Turn A/C on. Measure voltage between test pins No. 10 and 40. If voltage is greater than 10.5 volts, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST. If voltage is less than 10.5 volts, repair open in A/C circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

A/C Clutch Circuit. Scheme 25

Perform this test when directed by QUICK TEST. This test is intended to diagnose ECA and BOO circuit.

Brake On-Off (BOO) Switch Circuit. Scheme 26

1) Code 74/536: Verify Brake Pedal Was Depressed - Code 74/536 indicates that BOO signal did not cycle high and low when brake pedal was depressed and released during KOER SELF-TEST. Possible causes for this fault are

1. Brake pedal not depressed and released during KOER SELF -TEST.
2. Brake pedal depressed during entire KOER SELF-TEST.
3. Faulty ECA.
4. Faulty brake switch.
5. Open BOO/brakelight circuit.
6. Short to ground or power.

If brake pedal was depressed, go to next step. If brake pedal was not depressed during KOER SELF-TEST, repeat test. Depress and release brake pedal only once during test. Depress and release brake pedal after dynamic response code but before brief WOT.

2) Check Operation Of Brakelights - Turn ignition on. Check operation of brakelights. If brakelights operate normally, go to next step. If brakelights do not operate, go to step 4). If brakelights are always on, go to step 5).

3) Check For BOO Circuit Cycling - Turn ignition off. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 20-volt scale. Measure voltage between pin No. 2 of BOO vehicle harness connector and pin No. 40 at breakout box while depressing and releasing brake pedal. If voltage cycles, replace ECA. Remove breakout box, and rerun QUICK TEST . If voltage does not cycle, repair open in BOO circuit between ECA and BOO connection to brakelight circuit. Rerun QUICK TEST .

4) Check For Power To Brake Switch - Ensure related fuses and brakelight bulbs are in good condition. Turn ignition off. Disconnect brakelight switch (located on brake pedal). Measure voltage between BATT (+) input to brakelight switch and chassis ground. If voltage is more than 10 volts, verify operation of brakelight switch. If brakelight switch is okay, repair open in circuit between brakelight switch and brakelight ground. Reconnect brakelight switch connector, and rerun QUICK TEST . If voltage is less than 10 volts, repair open BATT (+) circuit to brakelight switch. Reconnect brakelight switch connector, and rerun QUICK TEST .

5) Verify Brake Switch Is Not Always Closed - Turn ignition off. Disconnect brakelight switch. Disconnect ECA. Turn ignition on, leaving engine off. If brakelights are still on, repair short to power in Boo/brakelight circuit. Reconnect all components, and rerun QUICK TEST . If brakelights are not on, replace ECA. Reconnect brakelight switch connector, and rerun QUICK TEST .

6) Check For Short To Power In ECA - Turn ignition off. Disconnect brakelight switch connector. Disconnect ECA. Turn ignition on, leaving engine off. If brakelights are still on, repair short to power in Boo/brakelight circuit. Reconnect all components, and rerun QUICK TEST . If brakelights are not on, replace ECA. Reconnect brakelight switch connector, and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 6) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 75/532: Check For Operation Of Brakelights - Code 75/531 indicates that BOO signal was high while brake pedal was released during KOER SELF-TEST. Possible causes for this fault are as follows.

1. Brake Pedal Depressed During Entire KOER SELF-TEST
2. Faulty Brakelight Switch
3. Faulty ECA
4. Open BOO/Brakelight Circuit (Between ECA And Brakelight Ground)
5. Short To POWER

Turn ignition on. Check brakelight operation. If brakelights operate normally, go to next step. If brakelights are always on, go to step 5). Ifbrakelights are never on, inspect brakelight bulbs. If bulbs are okay, repair open in circuit between BOO connection to brakelight circuit and brakelight ground. Rerun QUICK TEST .

11) Check Continuity Of BOO Circuit - Turn ignition off. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Disconnect brakelight switch connector. Measure resistance between test pin No. 2 at breakout box and brakelight switch vehicle harness connector terminal. If resistance is less than 5 ohms, replace ECA. Remove breakout box, reconnect brakelight switch connector and rerun QUICK TEST . If resistance is greater than 5 ohms, repair open in circuit between BOO connection to brakelight circuit and ECA. Remove breakout box, reconnect ECA and brakelight switch connector, and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 11) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 536: Check for Proper Brakelight Switch Installation - Code 536 indicates a BOO circuit failure. BOO input has failed if BOO input does not cycle after a predetermined number of transactions from zero MPH to a specific speed. Possible causes for this fault are as follows.

1. Brakelight/BOO Circuit Shorted To Power
2. Brakelight Switch Improperly Installed
3. Faulty Brakelight Switch
4. Faulty Brakelight Ground
5. Open Brakelight/BOO Circuit

Check brakelight switch for damage and proper installation. If brakelight switch is okay, go to next step. If brakelight switch is not okay, repair as necessary. Clear continuous memory, and rerun QUICK TEST .

91) Check Brakelight Ground - Check brakelight ground connections for damage. Check brakelight connector, terminals and wire for damage. If brakelight ground connections, connector, terminals and wires are okay, go to next step. If brakelight ground connections, connector, terminals and wires are not okay, repair as necessary. Clear continuous memory, and rerun QUICK TEST .

92) Check Brakelight/BOO Circuits For Short To Power - Turn ignition on, leaving engine off. DO NOT depress brake pedal. Wiggle brakelight/BOO circuit wires and connectors. Observe brakelights. If brakelights do not flash on while wiggling wires and connectors, go to next step. If brakelights flash on while wiggling wires and connectors, isolate short to power and repair as necessary. Clear continuous memory, and rerun QUICK TEST .

93) Check Brakelight Circuit Continuity - Turn ignition off. Depress and hold brake pedal. Wiggle brakelight circuit wires and connectors. Observe brakelights. Lightly tap brakelight switch to simulate road conditions. Observe brakelights. If brakelights do not go off, go to next step. If brakelights go off, isolate open in brakelight circuit and repair as necessary. Clear continuous memory, and rerun QUICK TEST .

94) Check BOO Circuit Continuity - Turn ignition off. Release brake pedal. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Connect DVOM between BOO test pin No. 2 at breakout box and brakelight circuit at brakelight switch. Set DVOM on 200-ohm scale. Wiggle BOO circuit connectors. Observe DVOM. If resistance is never greater than 5 ohms while wiggling connectors, go to INTERMITTENTS in TESTS W/O CODES article. If resistance is ever greater than 5 ohms while wiggling connectors, isolate open in BOO circuit and repair as necessary. Remove breakout box, reconnect ECA and rerun QUICK TEST .

Perform this test when directed by QUICK TEST. Fuel-contaminated engine oil may affect Codes 41/172 or 42/173. If this is suspected, remove PCV valve from valve cover and rerun QUICK TEST . If problem is corrected, change engine oil and filter.

This test is intended to diagnose ECA, HEGO sensor, HEGO signal and ground circuits, HEGO sensor connection, vacuum systems, fuel injectors and following harness circuits.

1. HEGO GROUND
2. HEGO INJ 1-6
3. SIG RTN
4. VPWR

Fuel Control Circuits. Scheme 27

To prevent replacement of good components, be aware that following non-EEC related areas and components may be cause of problem.

1. Air Filter
2. CANP Problems
3. Distributorless Ignition System
4. Engine Less Than Normal Operating Temperature
5. Fouled Spark Plugs
6. Fuel Or Engine Oil Contamination
7. Ignition Coil
8. Intake Or Exhaust Manifold Leaks
9. PCV Valves
10. Poor Power Ground
11. Spark Plug Wires.

INJECTOR RESISTANCE

FUEL PRESSURE SPECIFICATIONS

1) Check Fuel Pressure - Code 41/172 indicates system is lean and may indicate an exhaust odor/smoke condition. Loose HEGO Signal or HEGO ground connection or poor HEGO harness insulation near exhaust manifold will cause an intermittent fault causing ECA to determine a false lean condition to be present. Also check other non-EEC related areas and components that may be cause of problem. Code 42/173 indicates system is rich. Turn ignition off. Wait 10 seconds. Install fuel pressure gauge. Connect manifold vacuum to fuel pressure regulator (if applicable). Start engine, and operate it at idle. If engine will not start, cycle ignition off and on several times. Maximum fuel pressure is obtained at WOT or with vacuum hose disconnected from fuel pressure regulator. Check if fuel pressure is within specification. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, see FUEL SYSTEM in I - SYS/COMP TESTS - FUEL INJECTION article.

2) Check Ability Of System To Hold Fuel Pressure - Turn ignition on, leaving engine off. If fuel pressure remains at specification for 60 seconds and engine does not start, go to next step. If fuel pressure remains at specification for 60 seconds and engine runs rough and/or misses or Code 41, 42, 172 or 173 is present, remove fuel pressure gauge and go to step 4). If fuel pressure does not remain at specification for 60 seconds, go to step 6).

3) Fuel Delivery Test - Ensure fuel is good quality. Turn ignition off. Install fuel pressure gauge. Pressurize fuel system as in step 1). Disconnect inertia switch. Crank engine for 5 seconds. If fuel pressure drop is more than 5 psi after 5 seconds of cranking, EEC-IV system is not cause of no-start condition. Remove fuel pressure gauge, reconnect inertia switch and check additional no-start tests in TESTS W/O CODES article. If fuel pressure drop is less than 5 psi after 5 seconds of cranking, remove fuel pressure gauge, reconnect inertia switch and go to next step.

4) Check Injector & Harness Resistance - Turn ignition off. Wait 10 seconds. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Set DVOM on 200-ohm scale. Measure resistance of injector banks between test pins No. 37 and 58 (injector bank No. 1) or 37 and 59 (injector bank No. 2) at breakout box. See INJECTOR RESISTANCE table. If all readings are within specification, go to step 6). If any reading is not within specification, repair open in VPWR circuit (for no start) or go to next step.

5) Isolate Faulty Injector Circuit - Turn ignition off. With breakout box installed, disconnect ECA. Disconnect all injectors on suspected bank. Set DVOM on 200-ohm scale. Connect one injector and measure resistance between test pins No. 37 and 58 or 59 as required. Disconnect injector and repeat process for all other injectors. If all resistance readings are 13-16 ohms, go to next step. If any resistance reading is less than 13 ohms or greater than 16 ohms, repair open or short in VPWR circuit or in injector circuit of suspected injector. If circuits are okay, replace suspected injector. Remove breakout box, reconnect ECA and injectors. Drive vehicle for 5 miles at 55 MPH, and then rerun QUICK TEST .

6) Check Injector Drive Signal - Turn ignition off. With breakout box installed, connect ECA to breakout box. Connect a non-powered 12-volt test light between test pins No. 37 and 59 at breakout box. Crank or start engine. If test light glows dimly, system is operating properly. Go to next step. If test light does not light, check if 12 volts are present at test pins No. 37 and 57. If test light glows brightly, check for short to ground in injector circuit. If circuit is okay, replace ECA. Remove breakout box, and rerun QUICK TEST .

7) Check External Source For Fuel Pressure Problem - Turn ignition off. Pressurize fuel system as in step 1). Visually inspect fuel injector "O" rings, fuel pressure regulator and fuel rails for fuel leakage. If no visible leakage is found, go to next step. If fuel leakage is visible, remove fuel pressure regulator, repair leak as necessary and rerun QUICK TEST .

8) Injector Balance Test - Connect tachometer to engine. Operate engine at idle. Disconnect and then reconnect fuel injectors individually. Idle Speed Control (ISC) will try to reestablish RPM. If all injectors produce a momentary drop in RPM of at least 100 RPM, fuel system is okay. Check fuel system for other possible causes of problem. If any injectors do not produce a momentary drop in RPM of at least 100 RPM, see FUEL CONTROL in I - SYS/COMP TESTS - FUEL INJECTION article. Clean injectors, and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 8) to step 11). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

11) Code 41/172: Fuel Control Always Lean - Code 41/172 indicates system is lean. Run engine at 2000 RPM for 2 minutes. Turn ignition off, and wait 10 seconds. Rerun KOER SELF-TEST. If Code 41 or 172 is present, go to step 14). If Code 41 or 172 is not present, go to step 20).

Note. A break in step numbering sequence occurs at this point. Test skips from step 11) to step 14). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

14) Check HEGO Sensor - Purpose of this test is to verify HEGO sensor can generate a voltage signal of greater than .5 volt during KOER SELF-TEST. Vacuum or air leaks in non-EEC-IV related areas may cause Code 41/172 or 91/136. Following are possible causes for these faults.

1. Engine Seals
2. Leaking Vacuum Actuator (A/C Control Motor, Etc.)
3. PCV System
4. Unmetered Air Leaks Between MAF Sensor And Throttle Body
5. Lead-Contaminated HEGO Sensor

Turn ignition off. Disconnect HEGO sensor from vehicle harness. Connect DVOM between HEGO SIGNAL and HEGO GROUND at HEGO sensor connector. (Scheme 28) Set DVOM on 20-volt scale. Run engine at 2000 RPM for 2 minutes. Rerun KOER SELF-TEST, and monitor HEGO sensor voltage. If voltage is greater than.5 volt, go to next step. If voltage is less than.5 volt, replace HEGO sensor and rerun QUICK TEST.

Identifying HEGO Sensor Terminals. Scheme 28

15) Check Continuity Of HEGO SIGNAL & HEGO GROUND Circuits - Turn ignition off. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Disconnect HEGO sensor. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 46 and 49 at breakout box and HEGO GROUND at vehicle harness connector. (Scheme 29) If all readings are less than 5 ohms, go to next step. If any reading is greater than 5 ohms, repair open in circuit. Remove breakout box, and reconnect ECA, HEGO sensor and all other disconnected or removed components. Rerun QUICK TEST.

Identifying HEGO Sensor Vehicle Harness Terminals. Scheme 29

16) Check HEGO Circuit For Short To Ground - Turn ignition off. With breakout box installed, disconnect ECA. Disconnect HEGO sensor. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 29 and test pins No. 40, 46 and 49 at breakout box. If all resistance readings are greater than 10 k/ohms, go to next step. If any resistance reading is less than 10 k/ohms, repair short in circuit. Reconnect ECU and HEGO sensor. Rerun QUICK TEST.

17) Turn ignition off. With breakout box installed, disconnect ECA. Disconnect HEGO sensor. Set DVOM on 200-k/ohm scale. Measure resistance between PWR GROUND and HEGO SIGNAL at HEGO sensor connector. Measure resistance between PWR GROUND and SIG RTN at HEGO sensor connector. If all readings are less than 10 k/ohms, replace HEGO sensor. Reconnect ECA, and rerun QUICK TEST . If any reading is greater than 10 k/ohms, replace ECA. Remove breakout box, reconnect HEGO sensor and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 17) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) Check Resistance Of HEGO Heating Element - Turn ignition off. Disconnect HEGO sensor. Set DVOM on 200-ohm scale. Measure resistance between KPWR and PWR GND circuits at HEGO sensor connector. Hot to warm resistance should be 5-30 ohms. Room temperature resistance is 2-5 ohms. If resistance is within specification, go to next step. If resistance is not within specification, replace HEGO sensor and rerun QUICK TEST .

21) Check For Power At HEGO Harness Connector - Turn ignition on, leaving engine off. Disconnect HEGO sensor. Set DVOM on 20-volt scale. Measure voltage between KEY POWER and PWR GROUND circuits at HEGO vehicle harness connector. If voltage is less than 10.5 volts, go to next step. If voltage is greater than 10.5 volts, HEGO sensor system is okay. Reconnect HEGO sensor, and go to step 1).

22) Check Continuity Of Power Ground Circuit - Turn ignition off, and wait 10 seconds. Disconnect HEGO sensor. Set DVOM on 200-ohm scale. Measure resistance between PWR GROUND circuit at HEGO vehicle harness connector and battery negative post. If resistance is less than 5 ohms, repair open in KEY POWER circuit. Reconnect HEGO sensor, and rerun QUICK TEST. If resistance is greater than 5 ohms, repair open in PWR GROUND circuit. Reconnect HEGO sensor, and rerun QUICK TEST.

23) Code 42/173, 92/137 Or 177: Fuel Control Always Rich; Check HEGO SIGNAL For Short To Power - With dual HEGO sensors, Code 42/173 refers to right or rear HEGO sensor. Code 92/173 or 177 refers to left or front HEGO sensor. Code 42/173 indicates system is rich. Turn ignition off, and wait 10 seconds. Disconnect appropriate HEGO sensor for code present. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between HEGO SIGNAL and PWR GROUND circuits at HEGO vehicle harness connector. If voltage is less than .5 volt, go to next step. If voltage is greater than .5 volt, repair short to power in HEGO sensor circuit. Reconnect HEGO sensor, and rerun QUICK TEST .

24) Check HEGO Sensor For Short To Ignition Run Circuit - Turn ignition off. Disconnect HEGO sensor. Set DVOM on 200-k/ohm scale. Measure resistance between KEY POWER and HEGO SIGNAL circuits at HEGO sensor connector. If resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, replace HEGO sensor and rerun QUICK TEST .

25) Try To Generate Code 41/172, 91/136 Or 176 - Fuel- contaminated engine oil, ignition misfire (fouled spark plug) and CANP problems may cause these codes. Turn ignition off. Wait 10 seconds. Disconnect HEGO sensor. Using jumper wire, connect HEGO SIGNAL circuit at HEGO vehicle harness connector to negative battery post. Rerun KOER SELF-TEST. If Code 41, 91, 136, 172 or 176 is present, remove jumper wire and go to step 28). If Codes 41, 91, 136, 172 and 176 are not present, remove jumper wire and reconnect HEGO sensor. Disconnect and inspect ECA 60-pin connector. Repair as necessary. If connector is okay, replace ECA and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 25) to step 28). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

28) HEGO Sensor Check - Turn ignition off, and wait 10 seconds. Disconnect HEGO sensor. Connect DVOM to HEGO SIGNAL at HEGO sensor connector and to battery negative post. Set DVOM on 20-volt scale. Remove vacuum hose to create vacuum leak, which will cause HEGO sensor to go lean. Disconnect any vacuum hose from manifold vacuum tree. Disconnect PCV valve hose from PCV valve. Start engine, and run it at about 2000 RPM. DVOM should indicate less than .4 volt within 30 seconds. If voltage is not as specified, replace HEGO sensor. Reconnect vacuum hoses, and rerun QUICK TEST . If voltage is as specified, HEGO sensor is okay. Reconnect HEGO sensor and vacuum hoses, and go to step 1).

Perform this test when directed by QUICK TEST. This test is intended to diagnose ECA, fuel pump relay, inertia switch and following harness circuits.

1. BATT +
2. VPWR
3. FUEL PUMP
4. GND
5. POWER TO PUMP

Fuel Pump Circuits. Scheme 30

1) No Fuel Pump Pressure: Check Fuel Pump Electrical Operation - Turn ignition from OFF to RUN position several times ( DO NOT turn to START position). If fuel pump does not run, go to next step. If fuel pump run briefly each time ignition is turned to RUN position, fuel pump circuit is okay.

2) Check For VPWR To ECA - Turn ignition off. With breakout box installed, connect ECA. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between test pins No. 37 and 40 at breakout box. Measure voltage between pins No. 57 and 60 at breakout box. If all readings are greater than 10.5 volts, go to step 5). If any reading is less than 10.5 volts, go to TEST B.

Note. A break in step numbering sequence occurs at this point. Test skips from step 2) to step 5). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

5) Check For Voltage To POWER TO PUMP Circuit - Turn ignition on, leaving engine off. With breakout box installed, connect ECA. Set DVOM on 20-volt scale. Measure voltage between chassis ground and POWER TO PUMP circuit at fuel pump relay while cranking engine. If voltage is less than 8 volts, go to next step. If voltage is greater than 8 volts, check for open in POWER TO PUMP circuit, open in fuel pump and open fuel pump ground circuit.

6) Checking BATT (+) Circuit To Fuel Pump Relay - Turn ignition on, leaving engine off. With breakout box installed, connect ECA. Set DVOM on 20-volt scale. Measure voltage between chassis ground and BATT (+) circuit at fuel pump relay. If voltage is more than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open in BATT (+) circuit between fuel pump relay and positive battery post. Removebreakout box, reconnect ECA and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 6) to step 11). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

11) Check Voltage At POWER TO PUMP Circuit - Turn ignition off. With breakout box installed, disconnect ECA. Connect jumper wire from test pin No. 22 to test pin No. 40 or 60 at breakout box. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between chassis ground and POWER TO PUMP circuit at fuel pump relay. If voltage is greater than 10.5 volts, replace ECA. Remove breakout box, and rerun QUICK TEST. If voltage is less than 10.5 volts, replace fuel pump relay. Remove breakout box, reconnect ECA and rerun QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Test skips from step 11) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) Code 95: Check If Engine Starts - Code 95 indicates one of following conditions has occurred

No Starts

1. Inertia Switch Not Reset Or Electrically Open
2. Open Circuit In Or Between Fuel Pump And Fuel Pump Monitor (FPM) Circuit Connection To Power TO Pump Circuit
3. Faulty Ground Connection At Fuel Pump

Vehicle Starts

1. Fuel Pump Secondary Circuit Shorted To Power
2. Fuel Pump Relay Contacts Always Closed
3. Open In Fuel Pump Monitor (FPM) Circuit Between ECA And Connection To POWER TO PUMP Circuit
4. Faulty ECA

If engine starts, go to next step. If engine does not start, go to step 25).

21) Verify Fuel Pump Is Off - Turn ignition on and wait 5 seconds. Listen for fuel pump noise. If fuel pump is on, go to next step. If fuel pump is off, go to step 23).

22) Check For Fuel Pump Relay Always Closed - Turn ignition off. Disconnect fuel pump relay. Turn ignition on. If fuel pump is off with relay disconnected, replace fuel pump relay and rerun QUICK TEST . If fuel pump is on with relay disconnected, repair short to power in POWER TO PUMP/FPM circuit. Reconnect fuel pump relay, and rerun QUICK TEST.

23) Check Continuity Of Fuel Pump Monitor (FPM) Circuit - Turn ignition off. Disconnect and inspect ECA 60-pin connector. With breakout box installed, disconnect ECA. Disconnect fuel pump relay. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 8 at breakout box and POWER TO PUMP circuit at fuel pump relay vehicle harness connector. (Scheme 31) If resistance is less than 5 ohms, replace ECA. Remove breakout box, reconnect fuel pump relay and rerun QUICK TEST. If resistance is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

Fuel Pump Relay Vehicle Harness Connector. Scheme 31

24) Check Fuel Pump Circuit For Short To Ground - Turn ignition off. With breakout box installed, disconnect ECA. Disconnect fuel pump relay. Set DVOM on 200-k/ohm scale. Measure resistance between test pins No. 22 and 40 at breakout box. If resistance is greater than 10 k/ohms, replace ECA. Remove breakout box, reconnect fuel pump relay and rerun QUICK TEST. If resistance is less than 10 k/ohms, repair short in circuit. Remove breakout box, reconnect all components and rerun QUICK TEST .

25) Check Inertia Switch - Turn ignition off, and wait 10 seconds. Disconnect fuel pump inertia switch. Ensure switch is reset. 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 greater than 5 ohms, replace or reset inertia switch and rerun QUICK TEST .

26) Check For Continuity Between Fuel Pump Monitor (FPM) Circuit & Ground - Turn ignition off. With breakout box installed, disconnect ECA. Disconnect fuel pump relay. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 8 at breakout box and battery negative cable. If resistance is less than 10 ohms, replace ECA. Remove breakout box, reconnect fuel pump relay and rerun QUICK TEST . If resistance is greater than 10 ohms, remove breakout box and reconnect all components. Check for open in POWER TO PUMP circuit and fuel pump, for poor fuel pump ground and for faulty fuel pump.

Note. A break in step numbering sequence occurs at this point. Test skips from step 26) to step 30). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

30) Code 96/543: Engine Does Not Start - Code 96/543 indicates fuel pump secondary circuit failure between BATT (+) supply and FPM connection to POWER TO PUMP circuit: Possible causes for this fault are as follows.

1. Open Circuit
2. Fuel Pump Relay
3. Faulty ECA

Turn ignition off, and wait 10 seconds. Set DVOM on 20-volt scale. Measure voltage between BATT (+) circuit at fuel pump relay and negative battery post. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, repair open in BATT (+) circuit and rerun QUICK TEST.

31) Check For Voltage At POWER TO PUMP Circuit To Verify Fuel Pump Relay Operation - Turn ignition off. Connect fuel pump relay. Set DVOM to 20-volt scale. Connect DVOM between POWER TO PUMP circuit at fuel pump relay and negative battery terminal. Observe DVOM while activating fuel pump relay (turn ignition to RUN position for one second and then turn ignition off for 10 seconds. Repeat 5 times). If voltage is greater than 10.5 volts for about one second after key is turned to RUN position, replace ECA and rerun QUICK TEST. If voltage is less than 10.5 volts for about one second after key is turned to RUN position, replace fuel pump relay and rerun QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Test skips from step 31) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 95/542: Check EEC-IV Harness - Continuous Memory Code 95/542 indicates one of following conditions has occurred intermittently.

1. Open Circuit In Or Between Fuel Pump And FPM Circuit At ECA
2. Faulty Ground Circuit At Fuel Pump
3. FPM Or POWER TO PUMP Circuit Short To Power
4. Fuel Pump Relay Contacts Stuck Closed
5. FUEL PUMP Circuit Is Activated When ECA Expects Circuit To Be Off

Start engine, and perform wiggle test on POWER TO PUMP circuit between POWER TO PUMP pin at fuel pump relay and fuel pump. Also perform wiggle test on fuel pump ground circuit between fuel pump and ground. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Lightly tap inertia switch and fuel pump to simulate road shock. Check for engine miss or stumble while performing test. Turn ignition off. Check fuel pump vehicle harness connector and fuel pump ground for corrosion or damage. Isolate and repair any faults. Clear continuous memory, and rerun QUICK TEST . If fault is not present, go to next step.

91) Check FPM Circuit - Turn ignition off. With breakout box installed, disconnect and inspect ECA 60-pin connector. Turn ignition on, leaving engine off. Connect test light between test pins No. 8 and 37 at breakout box. With test light on, perform wiggle test on FPM circuit between fuel pump relay and ECA. Light should go out if fault is found during wiggle test. Isolate and repair any faults found. Remove breakout box, clear continuous memory and rerun QUICK TEST. If fault is not present, go to next step.

92) Check For Shorts To Power - Turn ignition on, leaving engine off. With breakout box installed, disconnect ECA. Connect test light between test pins No. 8 and 40. With test light off, perform wiggle test on FPM circuit and POWER TO PUMP circuit. Lightly tap fuel pump relay to simulate road shock. Light should come on if fault is found during wiggle test. Isolate and repair any faults found. Remove breakout box, reconnect ECA and clear continuous memory. Rerun QUICK TEST . If fault is not present, clear continuous memory and rerun QUICK TEST.

93) Continuous Memory Code 96/543: Check For Continuous Memory Code 87/556 - If Codes 87 and 556 are not present, go to next step. If Code 87 or 556 is also present, go to step 95).

94) Check EEC-IV Harness - A Continuous Memory Code 96/543, without an accompanying Continuous Memory Code 87/556, indicates one of following conditions has occurred during vehicle operation

1. An open in BATT (+) circuit between BATT (+) and fuel pump relay.
2. Fuel pump relay contacts open.
3. Open in POWER TO PUMP circuit from fuel pump relay to FPM splice (if applicable).

Start engine, and perform wiggle test on BATT (+) circuit between BATT (+) and fuel pump relay. Also perform wiggle test on POWER TO PUMP circuit between fuel pump relay and FPM splice (if applicable). See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Lightly tap fuel pump relay to simulate road shock. Check for engine miss or stumble while performing test. Turn ignition off. Check fuel pump relay connectors and BATT (+) connector terminal for corrosion and damage. Isolate and repair any faults. Clear continuous memory, and rerun QUICK TEST . If fault is not present, clear continuous memory and rerun QUICK TEST .

95) Continuous Code 87/556: Check EEC-IV Harness - A Continuous Memory Code 87/556 indicates primary fuel pump circuit has failed during vehicle operation. Possible causes for this fault are as follows.

1. Open In VPWR Circuit Between EEC Power Relay And Fuel Pump Relay
2. Open Coil In Fuel Pump Relay
3. Open In Fuel Pump Circuit (Pin No. 22)
4. Faulty Inertia Switch

Start engine, and perform wiggle test on VPWR circuit between EEC power relay and fuel pump relay. Also perform wiggle test on EEC vehicle harness fuel pump circuit (pin No. 22) between ECA and fuel pump relay. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under SELF-DIAGNOSTIC SYSTEM. Lightly tap fuel pump relay and inertia switch to simulate road shock. Check for engine miss or stumble while performing test. Turn ignition off. Check ECA 60-pin connector and fuel pump relay connectors for corrosion and damage. Isolate and repair any faults. Clear continuous memory, and rerun QUICK TEST . If fault is not present, clear continuous memory and rerun QUICK TEST .

Perform this test when instructed by QUICK TEST or when directed by other test procedures. This test is only intended to diagnose

1. CANP solenoid.
2. Harness circuits (CANP and VPWR).
3. ECA.

Canister Purge (CANP) Circuit. Scheme 32

TEST PIN WIRE COLOR IDENTIFICATION

1) Check System Function - Enter OUTPUT STATE CHECK. See OUTPUT STATE CHECK under ADDITIONAL SYSTEM FUNCTIONS. Use only VOM or DVOM for this step; DO NOT use diagnostic tester. Turn ignition 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 SIG RTN at self-test connector. Perform KOEO SELF-TEST until end of Continuous Memory Codes (DVOM reads zero volt). Depress and release throttle. DVOM should change to a high-voltage reading. If reading changes, remain in OUTPUT STATE CHECK and go to next step. If reading does not change, depress throttle to WOT and release. If STO voltage does not increase, leave test equipment hooked up and go to TEST QC .

2) Check CANP Solenoid Electrical Function - With Key On Engine Off (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 cycles, remain in OUTPUT STATE CHECK and go to next step. If CANP circuit does not cycle on and off, remove jumper wire and go to step 6).

3) Check Solenoid For Vacuum Leaks - Turn ignition on. Leave CANP solenoid disconnected. Disconnect vacuum hose at CANP solenoid from manifold vacuum side of solenoid. Apply 16 in. Hg to manifold vacuum side of CANP solenoid. If CANP solenoid does not hold vacuum for 20 seconds, replace solenoid and repeat QUICK TEST. If fault is still present, service fuel evaporation canister. If CANP holds vacuum for 20 seconds, remain in OUTPUT STATE CHECK, leave vacuum pump attached and go to next step.

4) Check Solenoid Mechanical Operation - While still in OUTPUT STATE CHECK, cycle CANP circuit off (no voltage). Reconnect CANP solenoid connector. Apply 16 in. Hg to the CANP solenoid as in step 3). Depress and release throttle. If vacuum is released, check hose from CANP solenoid to canister for leaks and cracks. If hose is okay, remove jumper wire from STI to SIG RTN and go to next step. If vacuum is not released, check hose from CANP solenoid to canister for leaks and cracks. If hose is okay, replace CANP solenoid and repeat QUICK TEST .

5) Check Vacuum Supply To CANP Solenoid - Disconnect vacuum hose from CANP solenoid on manifold vacuum (PCV) 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 improper routing, kinks and blockage. If hose is okay, check engine for cause of low vacuum.

6) Code 85/565: Check CANP Solenoid Resistance - Code 85/565 indicates fault in CANP solenoid circuit. Possible causes for this fault are as follows.

1. Faulty CANP Solenoid
2. Open in Harness Circuit
3. Shorted Harness Circuit (Power To Ground)
4. Faulty ECA

Turn ignition off. Wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect CANP solenoid connector. Measure CANP solenoid resistance. If reading is 40-90 ohms, go to next step. If reading is not 40-90 ohms, replace CANP solenoid and repeat QUICK TEST .

7) Check 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 negative battery terminal. If reading is 10.5 volts or more, go to next step. If reading is less than 10.5 volts, repair open in circuit and rerun QUICK TEST .

8) Check Continuity Of CANP Circuit - Turn ignition off, and wait 10 seconds. Disconnect CANP solenoid and ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as 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. Remove breakout box, reconnect components and repeat QUICK TEST .

9) Check CANP Circuit For Short To Ground - Turn ignition off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/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 10 k/ohms or more, go to next step. If any reading is less than 10 k/ohms, repair short to ground. Remove breakout box, reconnect components and repeat QUICK TEST .

10) Check CANP Circuit For Short To Power - Turn ignition off, and wait 10 seconds. Disconnect CANP solenoid. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 31 and test pins No. 37 and 57. If all reading are 10 k/ohms or more, remove breakout box. Replace ECA, and repeat QUICK TEST. If any reading is less than 10 k/ohms, repair short to power. Remove breakout box, reconnect components and rerun QUICK TEST. If code is repeated, replace ECA and rerun QUICK TEST .

Perform this test when instructed by QUICK TEST or when directed 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. This test is only intended to diagnose

1. RPM during self-test mode.
2. ISC solenoid.
3. Harness circuits (ISC and VPWR).
4. ECA

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

1. Engine Temperature Less Than Operating Temperature
2. Engine Temperature More Than Operating Temperature
3. A/C Input (Electrical Problem)
4. Incorrect Idle Speed Or Throttle Stop Adjustment
5. Faulty Cruise Control Linkage

Idle Speed Control (Air By-Pass) Circuit. Scheme 33

TEST PIN WIRE COLOR IDENTIFICATION

1) Code 12/412 Or 16: Check For RPM Drop - Code 12 indicates that engine RPM could not be controlled within upper RPM limit of self-test during KOER SELF-TEST. Possible causes for this fault are as follows.

1. Open Or Shorted Circuit
2. Sticking Or Binding Throttle Linkage
3. Incorrect Idle Adjustment
4. Throttle Body Or ISC Solenoid Contaminated
5. Faulty ISC Solenoid
6. Faulty ECA
7. Non-ECC Mechanical Faults That Could Affect RPM

2) Turn ignition off. Connect engine tachometer, and start engine. Disconnect Idle Speed Control (ISC) harness. If RPM drops or engine stalls, go to next step. If RPM does not drop or engine does not stall, go to step 4).

3) Check For Other EEC-IV Codes - Reconnect ISC solenoid if Code 22/126, 41/172, 42/173, 91/136 or 92/137 is displayed. Refer to the KOER SELF-TEST CODE REFERENCE table under KOER SELF-TEST, and perform appropriate TEST. If these codes are not displayed, go to next step.

4) Measure ISC Solenoid Resistance - Turn ignition off. Disconnect ISC solenoid. Set DVOM on 200-ohm scale and measure resistance of ISC solenoid. Connect DVOM positive lead to VPWR terminal and DVOM negative lead to ISC terminal, as ISC solenoid is equipped with a diode. (Scheme 34) If resistance is 6-13 ohms, go to next step. If resistance is not 6-13 ohms, replace ISC solenoid and repeat QUICK TEST.

ISC Solenoid Connector. Scheme 34

5) Check For Internal Short To ISC Solenoid Case - With ignition off and ISC solenoid disconnected, set DVOM on 200-k/ohm scale. Measure resistance from either ISC terminal pin to ISC solenoid housing. If reading is 10 k/ohms or more, go to next step. If reading is less than 10 k/ohms, replace ISC solenoid. Repeat QUICK TEST .

6) Check VPWR Circuit Voltage - 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) Check ISC Circuit Continuity - Turn ignition off. Wait 10 seconds. Leave ISC solenoid disconnected. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as 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 vehicle harness connector. If reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and repeat QUICK TEST . If reading is less than 5 ohms, go to next step.

8) Check ISC Circuit For Short To Ground - Turn ignition off. Wait 10 seconds. Leave ISC solenoid disconnected. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any reading is less than 10 k/ohms, repair short to ground and repeat QUICK TEST. If all readings are 10 k/ohms or more, go to next step.

9) Check ISC Circuit For Short To Power - Turn ignition off. Wait 10 seconds. Leave breakout box installed. Leave ECA and ISC solenoid disconnected. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage by connecting DVOM to test pin No. 21 and to ground. If reading is less than one volt, go to next step. If reading is one volt or more, repair short circuit and remove breakout box. Reconnect all components, and repeat QUICK TEST. If code or symptom is still present, replace ECA.

10) Check ISC Signal From ECA - With ignition off, reconnect 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 engine speed to 3000 RPM. If DVOM reading varies from 3.0-11.5 volts, go to next step. If DVOM reading does not vary (ensure ISC solenoid is not stuck open), replace ECA and repeat QUICK TEST .

11) Check Base Idle - Verify the base idle speed. Refer to the ADJUSTMENTS article. If base idle speed is within specification, 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 Affecting Idle Speed - Check following mechanical items for faults.

1. Throttle Linkage And/Or Cruise Control Linkage (Sticking Or Binding)
2. Throttle Body (Contamination)
3. Vacuum Hoses (Check Emission Decal)
4. Leaks Around ISC Solenoid (Gaskets, Etc.)

If all of these 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 these items are faulty, service as necessary. Remove breakout box. Reconnect components, and rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 12) to step 15). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

15) Code 13/411: Verify Idle Speed Is Within Specification -Code indicates that engine RPM could not be controlled within lower RPM limit of self-test during KOER SELF-TEST. Possible causes for this fault are as follows.

1. Incorrect Idle Setting
2. Vacuum Leaks
3. Sticking Or Binding Throttle Linkage
4. Throttle Plates Open
5. Throttle Body Or ISC Solenoid Contamination
6. ISC Circuit Shorted To Ground
7. Faulty ISC Solenoid

If all of the mentioned 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 next step.

16) Check For Conditions Affecting Idle Speed - Check following mechanical components.

1. Engine Vacuum Hoses (See VACUUM DIAGRAMS Article)
2. Throttle Linkage And/Or Cruise Control Linkage (Sticking Or Binding)
3. Ensure Throttle Plates Are Fully Closed
4. Induction System (Vacuum Leaks)
5. Throttle Body (Contamination)

If everything checks okay, go to next step. If fault is found, service as necessary and rerun QUICK TEST.

17) Check For Internal Short To ISC Solenoid Case - With ignition off and ISC solenoid disconnected, set DVOM on 200-k/ohm scale. Measure resistance from either ISC terminal pin to ISC solenoid housing. If reading is 10 k/ohms 66or more, go to next step. If reading is less than 10 k/ohms, replace ISC solenoid. Repeat QUICK TEST.

18) Check ISC Circuit For Short To Ground - Turn ignition off. Wait 10 seconds. Leave ISC solenoid disconnected. Disconnect ECA 60-pin connector. Inspect for damaged or corroded terminal pins. Service as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any reading is less than 10 k/ohms, repair short to ground and remove breakout box. Reconnect components, and repeat QUICK TEST . If all readings are 10 k/ohms or more, go to next step.

19) Check ISC Signal From ECA - With ignition 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 3.0-11.5 volts, remove ISC solenoid and inspect for contamination. Service as necessary, and 666rerun QUICK TEST. If code or symptom is still present, replace ISC solenoid. If DVOM voltage does not vary, replace ECA and rerun QUICK TEST .

Perform this test when diagnosing a symptom.

To prevent replacing good components, check following non-EEC components and systems.

1. Refrigerant Charge
2. Ambient Temperature Less Than 45°F (7.2°C)

This test is only intended to diagnose

1. Harness circuits (WAC, VPWR, GND, POWER TO CLUTCH, ACD).
2. WAC relay.
3. A/C fan controller.
4. ECA.

WOT A/C Cut-Out Circuits. Scheme 35

TEST PIN WIRE COLOR IDENTIFICATION

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 for this step. DO NOT use diagnostic tester. With ignition off, disconnectA/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 power side of A/C clutch vehicle harness connector and negative battery terminal. If voltage is 10.5 volts or more, EEC-IV system is okay. Diagnose A/C system. If voltage is less than 10.5 volts, go to next step.

2) Check Continuity Of Power-To-Clutch Circuit - Turn ignition off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect A/C clutch harness and harness from WAC relay. Measure resistance between power side of A/C clutch vehicle harness connector and power-to-clutch circuit terminal pin at WAC relay vehicle harness connector. If resistance is less than 5 ohms, reconnect A/C clutch and go to next step. If resistance is 5 ohms or more, service open circuit and retest system.

3) Check For Power On A/C Demand Circuit - With KOEO and WAC relay disconnected, turn on A/C switch. Set DVOM to 20-volt scale. Perform following procedure as applicable

1. Measure voltage between A/C demand input terminal pin at WAC relay vehicle harness connector and chassis ground.

If voltage is 10.5 volts or more, go to step 4). If voltage is less than 10.5 volts, verify operation of A/C clutch cyclic pressure switch and A/C demand switch. If components are okay, repair open circuit and reconnect all components. Recheck system.

4) Check WAC Circuit For Short To Ground - Turn ignition off. Wait 10 seconds. Disconnect ECA 60-pin connector and WAC relay. Inspect wiring, and repair if damaged. Leaving ECA disconnected, set DVOM on 200-k/ohm scale. Measure resistance between WAC circuit at WAC relay and chassis ground. If resistance is 10 k/ohms or more, go to next step. If resistance is less than 10 k/ohms, repair short. Reconnect all components, and recheck system operation.

Note. A break in step numbering sequence occurs at this point. Test skips from step 4) to step 9). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

9) Check WAC Relay - Turn ignition off, and wait 10 seconds. Leave ECA disconnected, and reconnect WAC relay. Disconnect A/C clutch. Set DVOM on 20-volt scale. With KOEO and A/C on, measure voltage between power side of A/C clutch vehicle harness connector and negative battery terminal. If voltage is 10.5 volts or more, replace ECA. Reconnect A/C clutch, and retest system. If voltage is less than 10.5 volts, replace WAC relay. Reconnect all components, and recheck system.

Note. A break in step numbering sequence occurs at this point. Test skips from step 9) to step 15). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

15) No A/C Output At WOT - Enter OUTPUT STATE CHECK. See OUTPUT STATE CHECK under ADDITIONAL SYSTEM FUNCTIONS. Use a VOM or DVOM for this test. Turn ignition off, and wait 10 seconds. Disconnect speed control servo electrical connector (if equipped). Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO at self-test connector and positive lead to positive battery terminal. Jumper STI to SIGNAL RETURN at self-test connector. Perform KOEO SELF-TEST until Continuous Memory Code output is completed. 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, depress throttle to WOT and release. If STO voltage does not increase, leave test equipment connected and go to TEST QC, step 2).

16) Check For 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 at WAC relay vehicle harness connector and chassis ground. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, repair open circuit between power relay and WAC relay. Remove test equipment, and retest system.

17) Check WAC System For Cycling - With vehicle in OUTPUT STATE CHECK, reconnect WAC relay and set DVOM on 20-volt scale. Connect positive test lead to VPWR circuit and negative test lead to WAC circuit at WAC relay vehicle harness connector. Check DVOM while depressing and releasing throttle several times to cycle output on and off. If voltage cycles from high to low, replace WAC relay. Remove jumper, and retest system. If voltage does not cycle, remove test leads. Reconnect speed control servo, and go to next step.

18) Check Continuity Of WAC Circuit - Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect 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 WAC relay vehicle harness connector. If reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and retest system. If reading is less than 5 ohms, go to next step.

19) Check WAC Circuit For Short To Power - Turn ignition off. Wait 10 seconds. Leave breakout box installed and ECA and WAC relay disconnected. Turn ignition on. Set DVOM on 20-volt scale. Measure voltage between test pin No. 54 and ground. If voltage is less than one volt, replace ECA. Reconnect WAC relay, and retest system. If voltage is one volt or more, repair short circuit. Reconnect all components, and retest system. If symptom is still present, replace ECA.

Note. A break in step numbering sequence occurs at this point. Test skips from step 19) to step 30). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

30) Cycle A/C Demand Switch - Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for corroded or damaged connector pins, and repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. With KOEO, connect DVOM positive test lead to test pin No. 43 and negative test lead to test pin No. 40. If voltage goes high and low as switch is cycled, replace ECA and rerun QUICK TEST . If voltage does not cycle, go to next step.

31) Check Continuity Of A/C Demand (ACD) Circuit - Turn ignition off. Wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 43 at breakout box and A/C demand switch. If resistance is 5 ohms or more, repair open in ACD circuit and rerun QUICK TEST . If resistance is less than 5 ohms, EEC-IV system is okay. Remove breakout box, and reconnect components. Diagnose A/C system.

Note. A break in step numbering sequence occurs at this point. Test skips from step 31) to step 35). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

35) Check A/C Demand (ACD) Circuit For Short To Power - With ignition off, disconnect WAC relay. Disconnect ECA 60-pin connector. Inspect for corroded or damaged connector pins, and repair as necessary. Install breakout box, leaving ECA disconnected. With A/C demand switch in OFF position, set DVOM on 20-volt scale. With KOEO, measure voltage between test pin No. 43 at breakout box and chassis ground. If voltage is less than one volt, EEC-IV system is okay. Remove breakout box, reconnect all components and diagnoseA/C system. If voltage is one volt or more, check operation of A/C demand switch. If switch operation is okay, repair short circuit. Remove breakout box, reconnect all components and retest system.

Note. A break in step numbering sequence occurs at this point. Test skips from step 35) to step 40). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

40) Check A/C Input - Ensure A/C switch is off. Disconnect ECA 60-pin connector. Install breakout box, leaving ECA disconnected. With key on, check for voltage between test pin No. 10 and ground. If more than one volt is present, repair short to power in A/C circuit. Remove breakout box, reconnect all components and retest system. If less than one volt is present between pin No. 10 and ground, replace ECA.

Enter this test when directed by QUICK TEST. This test is only intended to diagnose following systems or components.

1. Harness Circuits (SIG RTN, OCT ADJ)
2. Octane Shorting Bar Connector

Purpose of octane adjust shorting bar is to provide optimum spark advance for fuel used. If vehicle engine detonates (spark knock), remove octane shorting bar. This retards spark advance about 3-4 degrees. If vehicle continues to detonate, use fuel with a higher octane rating.

Octane Adjust Circuit. Scheme 36

TEST PIN WIRE COLOR IDENTIFICATION

1) Code 57/341 - Code 57/431 indicates Octane Adjust Shorting Bar is not in place or OCT ADJ circuit is open. Turn ignition off. Inspect Octane Adjust in-line connector. If shorting bar has been removed, go to step 2). If shorting bar is in place, go to step 4).

2) Check For Modification Decal - If vehicle has modification decal indicating OCT ADJ shorting bar was removed as a factory authorized procedure, testing is complete. If engine is detonating, go to TESTS W/O CODES article. If vehicle does not have modification decal, go to next step.

3) Check For Code 57/341 - Replace OCT ADJ shorting bar. Perform KOEO SELF-TEST. If Code 57/341 is present, go to next step. If code is not present, testing is complete. If driveability faults are present, go to TESTS W/O CODES article.

4) Check Octane Adjust Circuit Continuity - Continuity should exist from OCT ADJ circuit, through in-line connector and shorting bar, to SIG RTN circuit. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install breakout box, leaving ECA disconnected. Measure resistance between test pin No. 46 and OCT ADJ test pin at breakout box. If resistance is more than 5 ohms, repair open OCT ADJ circuit, shorting bar or SIG RTN circuit. Repeat QUICK TEST . If resistance is 5 ohms or less, replace ECA and repeat QUICK TEST .

5) Check For Code 11/111 - Start engine. Warm it to normal operating temperature. Turn ignition off. Perform KOEO SELF-TEST. If Code 11or 111 is present, go to next step. If Code 11 or 111 is not present, use higher octane fuel or check for other possible causes for Code 57/341. For all other codes, return to QUICK TEST .

6) Verify In-Line Shorting Bar Is Installed - Turn ignition off. Inspect Octane Adjust in-line connector. If shorting bar is not installed, go to next step. If shorting bar is installed, go to step 8).

7) Check For Modification Decal - If vehicle has modification decal indicating OCT ADJ shorting bar was removed as a factory authorized procedure, go to step 10). If vehicle does not have modification decal, replace shorting bar. If engine is still detonating, go to TESTS W/O CODES article.

8) Check For Technical Service Bulletin (TSB) - If a TSB authorizing removal of OCT ADJ shorting bar exists, go to next step. If a TSB authorizing removal of OCT ADJ shorting bar does not exist, testing is complete. If driveability faults are present, go to TESTS W/O CODES article.

9) Verify Drive Concern - Turn ignition off. Locate and remove shorting bar. Test drive vehicle to verify complaint. If detonation is present, go to next step. If detonation is not present, ECA system is okay. Testing is complete.

10) Check Octane Adjust Circuit For Short To Ground - Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install breakout box, leaving ECA disconnected. Measure resistance between OCT ADJ circuit at in-line connector and test pins No. 40, 46 and 60 at breakout box. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST . If each resistance is more than 10,000 ohms, go to next step.

11) Check ECA - Turn ignition off. Disconnect OCT ADJ shorting bar. Turn ignition on. Measure voltage between breakout box OCT ADJ test pin terminal and test pins No. 40 and 60. If voltage is less than 4 volts, replace ECA. If engine still detonates, go to TESTS W/O CODES article. If voltage is 4 volts or more, remove breakout box and go to TESTS W/O CODES article.

Perform this test only when directed by QUICK TEST. To prevent replacing good components, be aware that following non-EEC related areas may be cause of problem

1. Technician testing EEC system did not perform brief Wide Open Throttle (WOT) after Dynamic Response Code.
2. Mechanical engine components are faulty.
3. Engine did not go more than 2000 RPM during WOT.

This test is only intended to diagnose

1. Throttle movement (minimum 3/4 throttle).
2. RPM increase is greater than 2000 RPM.

If throttle is snapped open briefly, WOT test may not be passed. Ensure throttle is depressed fully to WOT and engine speed exceeds 2000 RPM.

1) Code 77/538 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 (Code 0 with STAR tester).
4. Observe Dynamic Response Code 1 (Code 0 with STAR tester).
5. Perform brief WOT.
6. Testing is complete; KOER code output begins.

If Code 77/538 is still displayed and engine speed was more than 2000 RPM, replace ECA and rerun QUICK TEST . If engine speed was not more than 2000 RPM, check throttle for binding and repair as necessary. If Code 77/538 is no longer present, vehicle has passed dynamic response test. Service other codes as necessary.

Perform this test only when instructed by QUICK TEST or when directed by TEST QA.

To prevent replacing good components, be aware that following non-EEC related areas may be cause of problem.

1. Fuse, Bulb Or Socket

This test is only intended to diagnose

1. STO/CHECK ENGINE light circuit.
2. ECA.
3. Data Communications Link (DCL).

CHECK ENGINE Light Circuit. Scheme 37

Data Communication Link (DCL) Circuit. Scheme 38

TEST PIN WIRE COLOR IDENTIFICATION

1) CHECK ENGINE Light Always On - If vehicle will not start, go to TEST AA. Service all other KOEO and Continuous Memory Codes before proceeding with this test. Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Connect DVOM between test pins No. 17 and 40 at breakout box. If resistance is 5 ohms or more, replace ECA. Remove breakout box, and rerun QUICK TEST . If reading is less than 5 ohms, repair short between test pin No. 17 and self-test connector or CHECK ENGINE light. Remove breakout box, reconnect all components and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 1) to step 5). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

5) CHECK ENGINE Light Never On: Check Continuity Of STO/CHECK ENGINE Light Circuit - If vehicle will not start, go to TEST AA . Turn ignition on, leaving engine off. Set DVOM on 200-ohm scale. Connect DVOM between test pin No. 17 and CHECK ENGINE light. If resistance is less than 5 ohms, go to next step. If reading is 5 ohms or more, repair open between test pin No. 17 and CHECK ENGINE light. Remove breakout box, reconnect all components and repeat QUICK TEST .

6) Check For Voltage To Bulb - Set DVOM on 20-volt scale. With Key On Engine Off (KOEO), measure voltage from negative battery post to hot side of CHECK ENGINE light bulb. If voltage is 10.5 volts or more, repair bulb or bulb socket. If bulb and bulb socket are okay, replace ECA. Reconnect ECA, and verify repair by turning ignition switch to RUN position. If voltage is less than 10.5 volts, go to next step.

7) Check For Voltage At Fuse - Set DVOM on 20-volt scale. With Key On Engine Off (KOEO), measure voltage from battery negative post to hot side of MIL fuse. If voltage is 10.5 volts or more, repair fuse or open circuit. Reconnect ECA and verify repair by turning ignition switch to RUN position. If voltage is less than 10.5 volts, repair MIL/VBAT circuit. Reconnect ECA, and verify repair by turning ignition to RUN position.

Note. A break in step numbering sequence occurs at this point. Test skips from step 7) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) CHECK ENGINE Light Intermittent: Check For Intermittent Short From STO To Ground - If vehicle does not start, go to TEST AA. Light comes on when a Continuous Memory Code is present. Service all Continuous Memory Codes before proceeding. If no codes are output, enter KOEO wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under SELF-DIAGNOSTIC SYSTEM. Observe DVOM for indication of fault while performing wiggle test on harness in following areas.

1. Self-Test Connector To Dash Panel
2. Dash Panel To ECA
3. 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. Testing for this fault is complete.

Note. A break in step numbering sequence occurs at this point. Test skips from step 10) to step 15). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

15) CHECK ENGINE Light Flashes With Erratic Idle: Check STI Circuit For Short To Ground - Vehicle symptoms indicate STI is grounded and ECA is performing self-test without tester installed. With ignition off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Set DVOM on 200-k/ohm scale. Measure resistance between STI connector and engine block ground. If resistance is less than 10 k/ohms, repair short circuit. Reconnect ECA and retest. If resistance is 10 k/ohms or more, reconnect ECA. Verify symptom, and test for other rough idle symptoms.

Ignition Diagnostic Monitor (IDM) is an input signal to ECA that verifies spark. Signal, which is transmitted from EDIS module to ECA, consists of a single pulse for each successful spark. Lack of an IDM pulse indicates intermittent of missing spark.

Perform this test only if Codes 14, 16, 18, 19 or 45 are retrieved during QUICK TEST or if sent here from another test. This test is only intended to diagnose EEC-IV portion of ignition system. For additional information on ignition system and component testing, see BASIC TESTING and I - SYS/COMP TESTS - FUEL INJECTION articles.

To prevent replacing good components, be aware that following non-EEC-related areas may be at fault.

1. EDIS Ignition Module
2. EDIS Coil Packs
3. Spark Plugs And/Or High Tension Cables
4. Variable Reluctance Sensor
5. Secondary Ignition Component Arcing

This test is intended to diagnose

1. Harness circuits for IGN GND, SPOUT, PIP, IDM, DPI and SAW.
2. ECA assembly.

Note. Unless specified otherwise, disconnect breakout box and reconnect all components after repairs.

1) Continuous Memory Code 211: Erratic Ignition - Code 211 indicates 2 successive erratic Profile Ignition Pick-Up (PIP) pulses occurred, resulting in a possible engine miss or stall. Possible causes for this fault are as follows.

1. Loose Wires Or Connectors
2. Arcing Secondary Ignition Components
3. Incorrectly Installed 2-Way Radio Or Misrouted Antenna Cable And Power Leads

If none of these problems are present, go to step 4). If any problems are present, repair as necessary. Clear codes. Rerun QUICK TEST .

2) Code 226: IDM Circuit Failure - If engine starts, go to step 4). If engine does not start, check EDIS system. See BASIC TESTING and I - SYS/COMP TESTS - FUEL INJECTION articles.

3) Continuous Memory Code 212: Check For Other Codes - Code 212 indicates loss of IDM input signal to ECA. Possible causes for this fault are as follows.

1. Open Or Shorted Harness
2. Faulty EDIS Module
3. Faulty ECA

If Continuous Memory Codes 215, 216 and 217 are not present, go to next step. If one or more of these codes is present, go to step 15).

4) Continuous Memory Code 212: Check IDM Circuit Continuity - Disconnect EDIS module. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Connect breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between breakout box test pin No. 4 and EDIS module harness connector pin No. 11. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Clear codes. Rerun QUICK TEST .

Note. During following test, a short to SIG RTN (test pin No. 26) may be indicated in conjunction with an actual PWR GND short if 4-wire HEGO is connected to harness.

5) Check IDM Circuit For Short To Ground - Disconnect EDIS module connector. Connect breakout box, leaving ECA disconnected. With DVOM on 200-k/ohm scale, measure resistance between breakout box test pin No. 4 and pins No. 40, 46 and 60. If resistance is more than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short to ground in IDM circuit. Clear codes. Rerun QUICK TEST .

6) Check ECA For Short To Ground - Disconnect EDIS module connector. Connect breakout box, leaving ECA disconnected. Set DVOM to 200-k/ohm scale. Measure resistance between breakout box test pin No. 4 and test pins No. 16, 20, 40, 46 and 60. If resistance is greater than 10 k/ohms, see TESTS W/O CODES article. If resistance is less than 10 k/ohms, replace ECA. Rerun QUICK TEST .

7) Check EDIS Module - Connect EDIS module connector. Connect breakout box, leaving ECA connected. Connect voltmeter betweenbreakout box test pins No. 4 and 16. Start engine. Allow voltage to stabilize. Lightly tap EDIS components to simulate road shock, and wiggle EDIS module connectors. If voltage does not change suddenly, leave voltmeter connected and go to next step. If voltage changes suddenly, disconnect and inspect EDIS connectors and terminals for damage. If connectors and terminals are okay, check EDIS ignition system. See BASIC TESTING and I - SYS/COMP TESTS - FUEL INJECTION articles.

8) Check EEC System Harness - Leave voltmeter connected as in previous step. Start engine. Check for sudden change in voltage while wiggling harness between EDIS module, other ignition system components and firewall. If voltage does not change suddenly, go to next step. If voltage changes suddenly, repair or replace components as necessary. Clear codes. Rerun QUICK TEST .

9) Check ECA & Connectors - Disconnect ECA 60-pin connector. If connector pins and wires are okay, return to step 6). If connector pins are damaged or corroded or if wires are loose, repair as necessary. Clear codes. Rerun QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Test skips from step 9) to step 15). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

15) Continuous Memory Code 45: Check Continuity Of Coil Circuits Between EDIS Module & Coil Pack - Coil pack has 3 coils. Code 45 indicates a fault has been detected by ECA in coils No. 3, 1 and 2, in that order.

1. Coil No. 1 supplies voltage for cylinders No. 3 and 4.
2. Coil No. 2 supplies voltage for cylinders No. 2 and 6.
3. Coil No. 3 supplies voltage for cylinders No. 1 and 5.

IDM pulse train contains a corresponding pulse for each operating coil. If a coil fails, corresponding pulse will be absent from pulse train. Possible causes of this fault include

1. Open in coil circuit between EDIS module and coil pack.
2. Short to coil circuit GND or PWR in EDIS module.

Turn ignition off. Wait 10 seconds. Set ohmmeter on 200-ohm scale. Measure resistance between

1. EDIS module connector pin No. 3 and ignition coil pack connector pin No. 1.
2. EDIS module connector pin No. 2 and ignition coil pack connector pin No. 2.
3. EDIS module connector pin No. 1 and ignition coil pack connector pin No. 3.

If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair circuit. Rerun QUICK TEST .

16) Check Coil Pack Circuits For Short To Ground Or Power - Turn ignition off. Disconnect EDIS module 12-pin connector. Disconnect coil pack connector. Set ohmmeter on 200-k/ohm scale. Measure resistance between

1. EDIS module connector pin No. 9 and pins No. 1, 2 and 3.
2. EDIS module connector pin No. 5 and pins No. 1, 2 and 3.

If resistance is less than 10 k/ohms, repair circuit. Rerun QUICK TEST . If resistance is greater than 10 k/ohms, check EDIS ignition system. See BASIC TESTING and I - SYS/COMP TESTS - FUEL INJECTION articles.

Spark Angle Width (SAW) is a digital signal generated by ECU. This signal provides spark timing information to EDIS module. Normally, only one SAW pulse will exist for each PIP pulse.

Perform this test when checking computed timing or when Code 18/213 is retrieved during QUICK TEST . This test is intended to diagnose

1. Harness circuit for SAW.
2. Base timing.
3. ECA.

To prevent replacing good components, be aware that following non-EEC-related areas may be at fault.

1. Basic Engine Condition (Valves, Vacuum Leaks, Valve Timing, EGR Valve, Etc.)
2. EDIS Module
3. Variable Reluctance Sensor (VRS).

TEST PIN WIRE COLOR IDENTIFICATION

Note. Unless specified otherwise, disconnect breakout box and reconnect all components after repairs.

Note. Before proceeding, check base timing according to procedure in COMPUTED TIMING CHECK under SELF-DIAGNOSTIC SYSTEM.

1) Check For Power To ECA - Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Connect breakout box, leaving ECA disconnected. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between breakout box test pins No. 37 and 40, and test pins No. 57 and 60. If both readings are 10.5 volts or more, go to next step. If either reading is less than 10.5 volts, go to TEST B.

2) Check SAW Circuit For Continuity - Disconnect EDIS module connector. Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between breakout box test pin No. 36 and SAW terminal at EDIS module connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Check base timing according to procedure in COMPUTED TIMING CHECK under SELF-DIAGNOSTIC SYSTEM.

3) Check SAW Circuit For Shorts To POWER, GROUND & PIP -Connect breakout box, leaving ECA disconnected. Disconnect EDIS module connector. Set DVOM to 200-k/ohm scale. To check for shorts to ground, measure resistance between breakout box test pin No. 36 and pins No. 16, 20, 40, 46 and 60. To check for shorts to POWER, measure resistance between test pin No. 36 and pins No. 26, 37 and 57. To check for short to PIP, measure resistance between test pins No. 36 and 56. If each resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short circuit. Rerun QUICK TEST .

4) Check SAW Voltage At ECA - Connect breakout box with ECA connected. Connect EDIS module connector. Set timing switch on breakout box to DIST position. Set DVOM on 20-volt AC scale. With engine running and in SELF-TEST mode, measure AC voltage between test pin No. 36 and negative battery post. If 0.01-1.89 volts AC is NOT present, replace ECA. Rerun QUICK TEST. If voltage is as specified, EEC-IV system is okay. Check EDIS ignition system. See BASIC TESTING and I - SYS/COMP TESTS - FUEL INJECTION articles.

Perform this test when directed by QUICK TEST or other test procedures. This test is only intended to diagnose

1. ECA.
2. EEC power relay.
3. Harness circuits for SIG RTN, STO, STI, VPWR, VREF and HEGO.

After-market devices, such as an alarm system, may cause self-test to abort if wiring is connected to certain EEC components. If a device is installed, disconnect it completely from EEC system. Before continuing with this circuit test, restore EEC circuits to original and rerun QUICK TEST .

No Codes/Codes Not Listed Circuit. Scheme 39

TEST PIN WIRE COLOR IDENTIFICATION

Note. Unless specified otherwise, disconnect breakout box and reconnect all components after repairs.

1) Check VREF Voltage At Self-Test Connector - Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Connect breakout box with ECA connected. Set DVOM on 20-volt scale. Turn ignition on, engine off. Measure voltage between breakout box test pin No. 26 and SIG RTN terminal at self-test connector. If reading is 4-6 volts, go to next step. If reading is not 4-6 volts, go to TEST C.

2) Check SIG RTN Circuit Continuity - Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between breakout box test pin No. 46 and SIG RTN terminal at self-test connector. If resistance is less than 5 ohms, go to TEST C. If resistance is greater than 5 ohms, repair open in circuit. Rerun QUICK TEST .

3) Check STI Circuit Continuity - Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between breakout box test pin No. 48 and Self-Test Input (STI) terminal at self-test connector. If reading is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in circuit. Rerun QUICK TEST .

4) Check STO Circuit Continuity - Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between breakout box test pin No. 17 and Self-Test Output (STO) at self-test connector. If reading is less than 5 ohms, go to next step. If reading is 5 ohms or more, repair open circuit. Rerun QUICK TEST .

Note. Due to ECU internal circuits, EEC strategy may not enter on-demand SELF-TEST if HEGO signal circuit is shorted to power,.

5) Check HEGO Signal For Short To Power - Connect breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Turn ignition on (engine off). Measure voltage between HEGO SIGNAL pin No. 29 or 44 and pin No. 40 or 60. (Scheme 27) If voltage is 2 volts or more, go to next step. If voltage is less than 2 volts, go to step 7).

6) Isolate Short To Harness Or HEGO Sensor - Connect breakout box, leaving ECA disconnected. Set DVOM to 20-volt scale. Disconnect HEGO sensor connector. Turn ignition on (engine off). Measure voltage between HEGO SIGNAL test pin No. 29 or 44 and test pin No. 40 or 60. (Scheme 27) If voltage is 2 volts or more, repair short to power in HEGO SIGNAL circuit. Rerun QUICK TEST. If voltage is less than 2 volts, replace HEGO sensor. Rerun QUICK TEST.

7) Check STO Circuit For Short To Ground - Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between engine block ground and STO terminal at self-test connector. If reading is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in STO or MIL circuit. Rerun QUICK TEST .

8) Check If Power Relay Is Always On - Connect breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Connect DVOM between test pin No. 37 and test pins No. 40 and 60. Turn ignition on and then off. Wait 10 seconds. Reading should change from more than 10.5 volts to less than one volt. In same manner, check voltage between test pin No. 57 and test pins No. 40 and 60. Reading should change from more than 10.5 volts to less than one volt. If reading does not change as specified, return to step 7). If reading changes as specified, go to next step.

9) Check VPWR Circuit For Short To Power - Connect breakout box, leaving ECA disconnected. Disconnect EEC power relay. Set DVOM on 20-volt scale. Turn ignition off. Connect DVOM between test pins No. 37 or 57 and test pins No. 40 or 46. If voltage is one volt or more, repair short to power in VPWR circuit. Rerun QUICK TEST . If voltage is less than one volt, replace EEC-IV power relay. Rerun QUICK TEST .

10) Check CHECK ENGINE Light Function (If Equipped) - If CHECK ENGINE light is always or never on, go to TEST ML , step 1) or step 5). If CHECK ENGINE light is working normally, replace ECA. Rerun QUICK TEST .

Continuous Memory Code 15/512 may be displayed when power to Keep-Alive Memory (KAM) test pin No. 1 at ECA is interrupted. This code may be set when connecting breakout box and may be displayed first time self-test is performed and power is restored to ECA. Repeat self-test to ensure correct diagnosis. Perform this test when directed by QUICK TEST. This test is only intended to diagnose following components or systems.

1. ECA
2. Harness Circuits For PWR GND, VPWR, KAPWR And IGNITION

Continuous Memory Code 15/512 Circuit. Scheme 40

TEST PIN WIRE COLOR IDENTIFICATION

Note. Unless specified otherwise, disconnect breakout box and reconnect all components after repairs.

1) Check KAPWR To ECA - Disconnect ECA 60-pin connector, and inspect it for damaged pins and loose wires. Service as necessary. Connect breakout box, leaving ECA disconnected. Turn ignition on (engine off). Set DVOM on 20-volt scale. Check voltage between breakout box test pin No. 1 and test pins No. 40 and 60 while wiggling, bending and shaking small sections of EEC harness between ECA and firewall. If reading is less than 10.5 volts, repair open circuit. Rerun QUICK TEST . If reading is 10.5 volts or more, reconnect ECA and go to next step.

2) Inspect Engine Compartment Wire Routing - Ensure EEC-IV components and wiring are not close to high-voltage secondary wires and ignition components. Reroute wiring as necessary. Clear codes. Wait 5 minutes. Run KOEO SELF-TEST. If Code 15/512 is not set, Continuous Memory Code 15/512 testing is complete. Service other codes as necessary. If Code 15/512 is set, replace ECA. Rerun QUICK TEST .

Perform this circuit test when directed by other CIRCUIT TESTS (TESTS).

This test is only intended to diagnose

1. Test conditions.
2. Throttle plate linkage.

Note. Unless specified otherwise, disconnect breakout box and reconnect all components after repairs.

1) Check For Codes 23, 53, 63, 121, 122 Or 123 - If vehicle is equipped with cruise control, disconnect cruise control servo electrical connector. This prevents cruise control system from affecting throttle plate movement during OUTPUT STATE CHECK. Rerun QUICK TEST or OUTPUT STATE CHECK. On all models, turn ignition off and wait 10 seconds. Perform KOEO SELF-TEST. If Code 23, 53, 63, 121, 122 or 123 is displayed, go to KOEO SELF-TEST CODE REFERENCE table under KOEO SELF-TEST. Service codes as necessary. If no codes are displayed, go to TEST QA . If Code 11 or 111 (pass code) is displayed, go to next step.

2) Check Throttle Linkage - Check throttle and linkage for sticking and binding. Repair as necessary. Rerun QUICK TEST . If throttle and linkage are okay, replace TPS. Rerun QUICK TEST .

Perform this test if Code 19/513 is present during QUICK TEST. Code 19/513 indicates ECA voltage regulator is not able to maintain proper internal voltage that is necessary for ECA to accurately compute data. This test is only intended to diagnose

1. ECA.
2. EEC power relay.
3. Harness circuits for GND, VPWR and IGNITION.

Note. numbering sequence begins at step 5) . This is due to previous chart references to this testing procedure. No test procedures have been omitted.

5) Code 19/513: Internal Voltage - Rerun KOEO SELF-TEST. Replace ECA if Code 19, 513, 510, 511 or 111 is present. Rerun QUICK TEST . If none of these codes are present, re-initialization check testing is complete. Service other codes as necessary.

Re-Initialization Check Circuit. Scheme 41

Perform this test only if Code 11/111 is present in during QUICK TEST or when directed here from another test. This test is intended to diagnose following components or systems.

1. Idle Speed Control/By-Pass Air (ISC/BPA) System
2. MAF System

To prevent replacing good components, be aware that following non-EEC-IV areas may be at fault.

1. Faulty Power Or Ground Connections
2. Ignition System (Distributor Cap, Rotor, Wires, Coil And Plugs)
3. Basic Engine Mechanical Condition (Cam Timing, Compression, Etc.)

1) ISC/BPA Check - Try to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to TEST KE, step 4). If engine does not function as described, go to step 3).

2) Check For RPM Drop - Turn ignition off. Connect a tachometer. Start engine. Disconnect ISC solenoid. If RPM drops or engine stalls, reconnect ISC solenoid and go to next step. If RPM does not drop, go to step 4).

3) Power To BP Sensor - Turn ignition off. Disconnect BP sensor connector. Connect BP tester between vehicle harness and BP sensor. (Scheme 42) Connect plugs of BP tester to DVOM. Set DVOM on 20-volt scale. Turn ignition on (engine off). If Green light is on, go to next step. If Green light is not on, repair open in VREF circuit. Disconnect BP tester. Reconnect components. Retest for symptom.

Note. If possible, measure several known-good BP sensors to obtain average voltage for specific elevation and time of testing.

4) BP Tester Output Reading - Connect BP tester and DVOM. Set DVOM on 20-volt scale. Turn ignition on. Measure BP SIG voltage. Compare measured voltage with voltage specified in BP VOLTAGE OUTPUT table. If voltage is within specification for specified elevation, go to TEST H . If voltage is not within specification, replace BP sensor.

BP VOLTAGE OUTPUT

BP Tester Circuit. Scheme 42

Perform this test only when directed by QUICK TEST. To prevent replacing good components, be aware that following non-EEC-related areas may be at fault.

1. Hydraulic Or Emergency Brake System
2. Transmission Linkage
3. Internal Transmission Components

This test only is intended to diagnose following components or circuits.

1. Harness Circuits For Converter Clutch Override (CCO), 3/4 -4/3 Shift Solenoid (SS 3/4) And VPWR
2. CCO Solenoid
3. SS 3/4
4. ECA

Code 86/566 indicates ECA did not detect a voltage drop when SS 3/4 was activated. Code 89/629 indicates ECA did not detect a voltage drop when CCO solenoid was activated. Possible causes for this fault are as follows.

1. Solenoid Resistance Out Of Limits
2. Solenoid Circuit Open Or Grounded
3. Faulty ECA

A4LD Transmission Circuits. Scheme 43

Note. Unless specified otherwise, disconnect breakout box and reconnect all components after repairs.

1) Code 86/566 Or 89/629: Check Solenoid Resistance - Ensure codes match appropriate transmission solenoid circuit. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Connect breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between breakout box test pins No. 37 and 52 and pins No. 57 and 53. If resistance is not 26-40 ohms, go to next step. If resistance is 26-40 ohms, go to step 4).

2) Check Continuity Of Harness - Connect breakout box, leaving ECA disconnected. Disconnect transmission bulkhead connector (A4LD solenoids). Set DVOM on 200-ohm scale.

1. Measure resistance between VPWR terminal at transmission connector and breakout box test pins No. 37 and 57.
2. Measure resistance between SS 3/4 terminal at transmission connector and breakout box test pin No. 52.
3. Measure resistance between CCO terminal at transmission connector and breakout box test pin No. 53.

If resistance is less than 5 ohms in each test, go to next step. If resistance is 5 ohms or more, repair open circuit. Rerun QUICK TEST .

3) Check For Short Circuits In Harness - Connect breakout box, leaving ECA disconnected. Disconnect transmission bulkhead connector. Set DVOM on 200-k/ohm scale.

1. Measure resistance between breakout box test pins No. 52 and 37, and test pins No. 57 and 53.
2. Measure resistance between breakout box test pin No. 52 and test pins No. 40, 46 and 60.
3. Measure resistance between chassis ground and breakout box test pins No. 40, 46 and 60.

If resistance in each test is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short circuit. Rerun QUICK TEST .

4) Check VPWR Voltage To Transmission Solenoids - Leaving ECA connected, connect breakout box. Set DVOM on 20-volt scale. Disconnect transmission bulkhead connector. Turn ignition on (engine off). Measure voltage between ground and VPWR terminal at transmission harness connector. If voltage is greater than 10.5 volts, go to next step. If voltage is 10.5 volts or less, replace ECA. Rerun QUICK TEST.

5) Check Output Driver Signal - Connect breakout box with ECA connected. Disconnect transmission bulkhead connector. Connect test light between breakout box test pins No. 37 and 52 and pins No. 57 and 53. Enter KOEO SELF-TEST. If test light flashes momentarily and then stays off, repair fault in transmission. If light does not flash momentarily and then stay off, replace ECA. Rerun QUICK TEST .

See also:
• CLEARING CODES
• KOER SELF-TEST CODE REFERENCE
• TEST AA
• COMPUTED TIMING CHECK
• KOEO SELF-TEST
• CONTINUOUS MONITOR MODE (WIGGLE TEST)