Engine Controls - Tests W/codes - 5.0l Ford Econoline E350

INTRODUCTION

Note. Unless otherwise specified, references to Pickup include the F350 Super Duty commercial chassis.

Perform all steps in BASIC TESTING article in the ENGINE PERFORMANCE Section. If no fault is found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with self-diagnostics. If no service code or only pass codes are found during self-diagnostics, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptoms.

SELF-DIAGNOSTIC SYSTEM

DIAGNOSTIC FORMATS

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

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

DIAGNOSTIC TROUBLE CODES

During QUICK TEST, 3 types of service codes are retrieved: KOEO, KOER and Continuous Memory codes. See QUICK TEST for self-test procedures. Codes may be cleared from ECA memory 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 or Malfunction Indicator Light (MIL) 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 SERVICE CODE REFERENCE CHARTS to find correct testing and repair procedures.

CONTINUOUS MEMORY CODES (SOFT FAULTS)

These codes indicate a fault that may or may not be present at time of testing. These codes are used to diagnose intermittent problems. Continuous Memory Codes are retrieved during KOEO SELF-TEST. Some codes may turn on MIL or CHECK ENGINE light. Corresponding soft trouble code will be retained in ECA memory. If fault does not reoccur within 40 warm-up cycles (80 cycles on some models), ECA will automatically clear code.

Technician may clear service codes from memory. See CLEARING CODES. Intermittent faults may be caused by a sensor, connector or wiring-related problems. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

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. Scan Tester
3. In-Dash Malfunction Indicator Light (MIL) Or CHECK ENGINE Light

SELF-TEST CONNECTOR LOCATIONS

KOEO & KOER SELF-TEST CODES

All service codes are 2- or 3-digit numbers. ECA outputs codes one digit at a time. These codes indicate current faults in system and should be serviced in order of appearance. Use SERVICE CODE REFERENCE CHARTS to find correct CIRCUIT 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 needle sweeps. (Scheme 77)

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 77)

SEPARATOR CODE

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

PASS CODES

Code 11 or 111 indicates system passes that portion of test. If Code 11 or 111 is not retrieved in KOEO SELF-TEST, codes retrieved during KOER SELF-TEST may not be valid. Code 11-1-11 or 111-1-111, output during KOEO SELF-TEST, indicates no KOEO code or Continuous Memory Code was recorded.

CONTINUOUS MEMORY CODES

Continuous Memory Codes are displayed after separator pulse code in KOEO SELF-TEST. These codes result from information stored by ECA during continuous self-test monitoring. These codes indicate faults recorded within last 40 engine starts (80 engine starts on some models). Fault may or may not be currently present. See SERVICE CODE REFERENCE CHARTS. Use these codes for diagnosis only when KOEO SELF-TEST and KOER SELF-TEST result in Code 11 or 111.

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, which were used by manufacturer during assembly. With most equipment, these code bursts are not visible; an entire code sequence lasts less than 1/2 second. If this fluctuation is visible on test equipment, ignore it.

Scheme 77

CLEARING CODES

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 STAR Series Tester, unlatch center button. This procedure erases Continuous Memory Codes from ECA memory. If problem has not been corrected or fault is still present, hard code will immediately be reset in ECA memory.

Note. To clear KAM, disconnect negative battery terminal for at least 5 minutes.

DESCRIPTION

Following procedures are functional tests of EEC-IV system. (Scheme 79) These 5 basic test steps must be carefully followed in sequence to avoid misdiagnosis or replacement of non-faulty components.

1. Visual Check & Vehicle Preparation
2. Equipment Hookup
3. KOEO (Key On Engine Off) SELF-TEST
4. Computed Timing Check
5. KOER (Key On Engine Running) SELF-TEST

Diagnostic Aids

After each service or repair procedure has been completed, repeat QUICK TEST to ensure all EEC-IV systems work properly and fault codes are no longer present.

VISUAL CHECK & EQUIPMENT HOOKUP

Complete all steps in BASIC TESTING article in the ENGINE PERFORMANCE Section before proceeding to self-diagnostic tests. Ensure vacuum hoses and EEC-IV wiring harnesses are properly connected.

Apply parking brake, and place shift lever in PARK (A/T) or NEUTRAL (M/T) position. Block drive wheels. Turn off all electrical loads. Connect appropriate test equipment to vehicle as follows

Analog Volt-Ohmmeter (VOM)

1) Turn ignition switch to OFF position. Set VOM at 0-15V 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. (Scheme 78) 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.

Scan Tester

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

STAR Series Tester

Turn ignition switch to OFF position. Connect color-coded adapter cable leads to diagnostic tester. Connect 2service connectors of adapter cable to vehicle self-test connector and STI pigtail connector. Connect timing light. Go to KOEO SELF-TEST.

Scheme 78

Scheme 79

KOEO SELF-TEST

Ensure engine is warmed to normal operating temperature. If engine does not start (or stalls after starting), continue KOEO SELF-TEST. DO NOT depress throttle on gasoline vehicles. Turn ignition off. Wait 10 seconds. Ensure test equipment is properly attached. Turn ignition on (engine off). Record all KOEO and Continuous Memory Codes.

If a Code 11 or 111 (pass code) is not retrieved in KOEO portion of test, service KOEO codes. See SERVICE CODE REFERENCE CHARTS. If ECA will not output codes, go to CIRCUIT TEST QA. If service codes are retrieved

1. Service codes in order retrieved. See SERVICE CODE REFERENCE CHARTS.
2. On DIS and EDIS models, see IGNITION SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section if Continuous Memory Code 45, 46, 48, 215, 216, 217, 232 or 238 is retrieved during KOEO SELF-TEST.
3. If vehicle has a no-start condition, go to CIRCUIT TEST AA (TFI), CIRCUIT TEST AB (DIS) or CIRCUIT TEST AC (EDIS).
4. If vehicle displays a Code 11 or 111 (pass code) and does not have any of symptoms described in previous steps, go to COMPUTED TIMING CHECK.

COMPUTED TIMING CHECK

Turn ignition off. Connect timing light. Using jumper wire or test equipment, activate KOER SELF-TEST. If engine starts and stalls (or stalls during self-test), go to CIRCUIT TEST S. Start engine, and check for following

1. 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.
2. 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.
3. Computed timing, at crankshaft, should equal base timing (see vehicle emission decal) 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 step 2) of CIRCUIT TEST PA (TFI), of CIRCUIT TEST PB (DIS) or of CIRCUIT TEST PC (EDIS).

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, codes recorded in KOER SELF-TEST may not be valid.

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 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 CIRCUIT TEST S.
2. If Code 98 or 998 is displayed, EEC-IV system is operating in Failure Management Effects Mode (FMEM) and vehicle has not passed KOEO SELF-TEST. Vehicle cannot be diagnosed while in FMEM mode. See Code 98 or 998 in SERVICE CODE REFERENCE CHARTS.
3. If vehicle is equipped with a Brake On-Off (BOO) switch, brake pedal must be depressed and released after ID code portion of test.
4. On vehicles with Power Steering Pressure Switch (PSPS), turn steering wheel at least 1/2 turn and release within 1-2 seconds after ID code portion of test.
5. On vehicles with E4OD transmissions, Overdrive Cancel Switch (OCS) must be cycled after ID code portion of test.
6. If Dynamic Response Code appears, perform a brief Wide Open Throttle (WOT). DO NOT perform WOT unless requested.
7. If a Code 11 or 111 (pass code) is retrieved during KOER SELF-TEST, service Continuous Memory Codes retrieved in KOEO SELF-TEST. See SERVICE CODE REFERENCE CHARTS.
8. If a Code 11 or 111 (pass code) is retrieved during Continuous Memory Code portion of KOEO SELF-TEST (Code 11-1-11 or Code 111-1-111) and no driveability problem exists, EEC-IV testing is complete. If driveability problems are still present, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
9. If KOER codes are present, see SERVICE CODE REFERENCE CHARTS. If system will not output codes, go to CIRCUIT TEST QA.

CONTINUOUS MONITOR MODE (WIGGLE TEST)

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

KOEO Wiggle Test

Connect test equipment. Turn ignition on, and activate self-test using jumper lead or diagnostic tester. Wait 10 seconds, and then deactivate and reactivate self-test. Wiggle test mode is now activated. 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 diagnostic tester or scan tester. Retrieve code, and perform appropriate test. See SERVICE CODE REFERENCE CHARTS.

KOER Wiggle Test

Connect test equipment. Turn ignition off, and wait 10 seconds. Start engine. Activate self-test using jumper lead or diagnostic tester. Wait 10 seconds, and then deactivate and reactivate self-test. DO NOT turn engine off. KOER wiggle test mode is now activated. 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 diagnostic tester or scan tester. Retrieve code, and perform appropriate test. See SERVICE CODE REFERENCE CHARTS.

ADDITIONAL SYSTEM FUNCTIONS

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

CHECK ENGINE Light & Malfunction Indicator Light (MIL)

CHECK ENGINE light and MIL are 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.

Light should come on when ignition is turned on and go out when engine is started. If light does not come on, see SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If hard fault codes are not present, ECA turns out light when it receives a Profile Ignition Pick-Up (PIP) signal.

Output State Check

Output state check is used as an aid for servicing EEC-IV system output actuators. It allows technicians to operate most output actuators on command. This mode is entered from KOEO SELF-TEST after all codes have been retrieved. Leave SELF-TEST activated, and depress throttle to initiate test sequence. Each time throttle is depressed and released, output actuators will change 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 that are out of normal operating range. During FMEM mode, ECA substitutes a mid-range signal for defective sensor while continuing to monitor sensor. 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. Driveability performance will be reduced.

Cylinder Balance Test

This test helps identify a weak or non-contributing cylinder in engines with sequential PFI fuel systems. ECA shuts off fuel supply to each injector and measures RPM drop. It computes variation between cylinders and identifies weak ones. This test mode is entered from KOER SELF-TEST after all codes have been displayed. Within 2 minutes after codes have been displayed, lightly depress throttle (a 2-3 degree throttle angle is required, not a wide open throttle). After a brief stabilizing period, ECA will activate test procedure. Test will be repeated if throttle is depressed within 2 minutes of final code output. During second and third test sequences, percentage of allowable variation between cylinders is reduced. Service codes displayed during this test identify weak or non-contributing cylinder. See CYLINDER BALANCE TEST SERVICE CODES . If Code 90 is displayed during this test, system has passed test. If Code 77 is displayed, repeat cylinder balance test. If throttle is moved during this test, Code 77 will appear, indicating test is not completed. Total test time is about 3 minutes.

CYLINDER BALANCE TEST SERVICE CODES

DIAGNOSTIC TROUBLE CODE CHART (CODE 11-56). Scheme 80

DIAGNOSTIC TROUBLE CODE CHART (CODES 57-99). Scheme 81

DIAGNOSTIC TROUBLE CODE CHART (CODE 111-185). Scheme 82

DIAGNOSTIC TROUBLE CODE CHART (CODE 186-339). Scheme 83

DIAGNOSTIC TROUBLE CODE CHART (CODE 341-619). Scheme 84

DIAGNOSTIC TROUBLE CODE CHART (CODE 621-998). Scheme 85

DIAGNOSTIC TROUBLE CODE DEFINITION (VAN 5.0L)

DIAGNOSTIC TROUBLE CODE DEFINITION

DIAGNOSTIC TROUBLE CODE DEFINITION (BRONCO & PICKUP 5.0L WITH E4OD)

SERVICE CODE DEFINITION

DIAGNOSTIC TROUBLE CODE DEFINITION (BRONCO & PICKUP 5.0L WITHOUT E4OD)

SERVICE CODE DEFINITION

CIRCUIT TESTS

Note. A breakout box, connected to vehicle harness at ECA, is necessary to perform most circuit tests. References to Test Pin No. found in CIRCUIT TEST steps refer to test terminals on manufacturer breakout box overlay. Circuit diagrams at beginning of each test identify circuit and wire colors.

HOW TO USE CIRCUIT TESTS

1) Ensure all non-EEC-IV related faults found while performing steps in BASIC TESTING article in the ENGINE PERFORMANCE Section have been corrected. DO NOT perform any CIRCUIT 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) CIRCUIT 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 CIRCUIT TESTS.

3) DO NOT measure voltage or resistance at ECA. DO NOT connect any test light unless specified in testing procedure. All measurements are made by probing rear of connector. Isolate both ends of a circuit and turn 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.

5) An open circuit is defined as a resistance reading of greater than 5 ohms. This specification tolerance may be too high for some items in EEC-IV system. If resistance approaches 5 ohms, always clean suspect connector and coat it with protective dielectric silicone grease. A short is defined as a resistance reading of less than 10,000 ohms to ground, unless stated otherwise in CIRCUIT TEST.

Fuel-contaminated engine oil may affect some codes. If oil is suspect, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil.

On CIRCUIT TEST H and CIRCUIT TEST J, vacuum leaks in non-EEC related areas may cause Code 41 or 91 to be displayed. Check vacuum motors, engine seals, EGR system, PCV system, Canister Purge (CANP), HEGO sensor and between airflow meter and throttle body for unmetered air leaks. Code 42 or 92 may be caused by fuel-contaminated engine oil, ignition misfire, or EGR system or CANP problems.

Note. In following tests, circuit diagrams and illustrations are courtesy of Ford Motor Co.

CIRCUIT TESTS are grouped as follows.

1. A-C - No Start & Voltage Tests
2. DA-DS - Input Sensor Tests
3. FD-FF - Additional Input Component Tests
4. G-J - Fuel Control System Tests
5. KC-TG - ECA (Processor) Output Tests

CIRCUIT TEST INDEX

CIRCUIT TEST AA - NO START (TFI IGNITION SYSTEMS)

Enter this CIRCUIT TEST only when steps in QUICK TEST have been successfully completed but engine still does not start or if directed here from another test or chart.

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

1. Thick Film Ignition (TFI) Systems
2. Electronic Control Assembly (ECA)
3. Spark (ECA-controlled)
4. Wiring Harness Circuits (PIP, SPOUT, IGN GND And VPWR)

Note. Vehicles are equipped with either a Closed Bowl Distributor (CBD) TFI module (remote mounted) or a standard TFI module (distributor mounted).

Distributor Mounted TFI Module Circuits. Scheme 86

Remote Mounted TFI Module Circuits. Scheme 87

CIRCUIT TEST AA TEST PIN WIRE COLOR ID

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

1. Fuel quality and quantity.
2. Ignition (general system condition).
3. Engine mechanical components.
4. Starter and battery circuits.
5. Dual Hall sensor.
6. Distributor.
7. Camshaft (CID) sensor.
8. Crankshaft (PIP) Hall sensor.
9. Ignition coil.

1) Starting System Try to start engine. If engine does not crank, check vehicle starting and charging systems. If engine cranks, verify inertia switch button is pushed in. If inertia switch button is pushed in, go to step 2).

2) Check VREF Signal At TPS Turn ignition off, and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect Throttle Position Sensor (TPS). Turn ignition on (engine off). Measure voltage at TPS harness connector between VREF and SIG RTN. (Scheme 88) If voltage is 4-6 volts, reconnect TPS and go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

TPS Harness Connector Terminal ID. Scheme 88

3) Check For Spark At Plugs Disconnect any spark plug wire. Connect spark tester between spark plug wire and ground. Crank engine and check for spark. If spark is present and consistent, connect spark plug wire and go to step 13). If spark does not exist, connect spark plug wire and go to step 4).

4) Check For Spark At Coil Remove high-tension coil wire from distributor. Install spark tester. Check for spark while cranking engine. If spark exists, connect coil wire, and service ignition secondary system. If no spark exists, connect coil wire and go to step 5).

5) Check Ignition Circuit Ground Continuity Turn ignition off. Wait 10 seconds. Disconnect and inspect ECA 60-pin connector. Install Break-out Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect TFI module. Disconnect Hall sensor or Crank Angle Sensor (CAS) if equipped. Measure resistance between test pin No. 16 at breakout box and IGN GND circuit of TFI, Hall sensor or CAS harness connector. If reading is more than 5 ohms, repair open in IGN GND circuit and repeat QUICK TEST. If reading is 5 ohms or less, go to step 6).

6) Isolate SPOUT Circuit Fault Connect TFI module, CAS or distributor hall connector as applicable. Connect ECA to breakout box. Set break-out box timing switch to DIST position. Try to start vehicle. If vehicle starts, go to step 11). If vehicle does not start, go to step 7).

7) Check SPOUT Signal Turn ignition off. Move breakout box timing switch to DIST position. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between test pin No. 36 at breakout box and negative battery terminal while cranking engine. If voltage is 3-6 volts, EEC-IV system is not at fault. Diagnose ignition system. See TFI-IV SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If voltage is not 3-6 volts, go to step 8).

8) Check SPOUT & PIP Circuits For Short Circuit Turn ignition off. With breakout box installed, move timing switch to COMPUTED position. On models with remote mounted TFI-IV module, disconnect distributor connector; on all other models, disconnect TFI module. Disconnect ECA. Turn ignition on. Measure voltage between test pin No. 36 (SPOUT) and negative battery terminal. Measure resistance between test pin No. 56 (PIP) and negative battery terminal. If voltage is more than 10.5 volts, repair circuit for a short to power and repeat QUICK TEST. If engine still does not start or if all voltages are 10.5 volts or less, go to step 9).

9) Turn ignition off. On models with remote mounted TFI-IV module, disconnect distributor connector; on all other models, disconnect TFI module. Measure resistance between test pin No. 36 (SPOUT) and test pins No. 16, 20, 40, 46 and 60 for short to ground. Measure resistance between test pin No. 36 and test pin No. 56 for short to PIP. Measure resistance between test pin No. 56 (PIP) and test pins No. 16, 20, 40, 46 and 60. If all readings are 10,000 ohms or more, go to step 10). If any reading is less than 10,000 ohms, repair short in harness and repeat QUICK TEST. If engine still does not start, go to step 10).

10) Isolate Shorts In ECA Turn ignition off. With breakout box installed, reconnect ECA. Measure resistance between test pin No. 36 (SPOUT) and test pins No. 37, 40, 57 and 60. Measure resistance between test pin No. 56 (PIP) and test pins No. 37, 40, 57 and 60. If any reading is less than 500 ohms, replace ECA and repeat QUICK TEST. If all readings are 500 ohms or more, connect TFI and go to step 11).

11) Check PIP Signal Turn ignition off. Set DVOM on 20-volt scale. With breakout box installed, move timing switch to COMPUTED position. While cranking engine, measure voltage between test pin No. 56 (PIP) and test pins No. 40 and 60. If voltage is 3-7 volts, replace ECA. Repeat QUICK TEST. If voltage is not 3-7 volts, go to step 12).

12) Check Continuity Of PIP Circuit Turn ignition off. Disconnect ECA from breakout box. On models with remote mounted TFI-IV module, disconnect distributor connector; on all other vehicles, disconnect TFI module. Measure resistance between test pin No. 56 and distributor or TFI module connector PIP circuit. If resistance is 5 ohms or more, repair open PIP circuit and repeat QUICK TEST. If resistance is less than 5 ohms, remove breakout box and diagnose ignition system. See TFI-IV SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

13) Verify SPOUT Signal If spark was present in step 3), turn ignition off. Disconnect ECA 60-pin connector. Inspect for damaged pins and repair as necessary. Install breakout box, and connect ECA. Ensure breakout box timing switch is in COMPUTED position. Set DVOM on 20-volt scale. Measure voltage between test pin No. 36 and pins No. 40 and 60 while cranking engine. If voltage is 3-6 volts, go to step 20). If voltage is not 3-6 volts, return to step 8).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.

20) Fuel Pump Check Connect fuel 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 CIRCUIT TEST S. If pressure does not increase, go to step 21).

21) Inertia Switch Resistance Check Turn ignition off. Locate fuel pump inertia switch. Ensure button on switch is pushed down to ON position. Measure resistance of switch. If resistance is 5 ohms or more, replace switch. If resistance is less than 5 ohms, inertia switch is okay. For additional fuel system test procedures, see FUEL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

Enter this CIRCUIT TEST only when directed by CIRCUIT TEST C, CIRCUIT TEST J, CIRCUIT TEST PA, CIRCUIT TEST PB or CIRCUIT TEST PC. To prevent replacement of good components, be aware following non-EEC related areas may be cause of problem: battery cables, ground straps, voltage regulator, alternator and ignition switch. This test is intended to diagnose ECA, power relay, battery voltage and following harness circuits.

1. Signal Return
2. PWR GND
3. VPWR
4. KAPWR
5. VREF
6. Ignition Switch

Identifying Power Relay Ckts. (Van). Scheme 89

Identifying Power Relay Ckts. (Bronco & Pickup). Scheme 90

CIRCUIT TEST B TEST PIN WIRE COLOR ID

1) Battery Voltage Check Turn ignition on (engine off). Measure battery voltage. If voltage is less than 10.5 volts, recharge or replace battery. If voltage is 10.5 volts or more, go to step 2).

2) Check Continuity Of PWR GND Circuit Turn ignition off. Wait 10 seconds. Disconnect ECA. Inspect connector pins for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Measure resistance between test pins No. 40 and 60 at breakout box and negative battery terminal. If resistance is 5 ohms or more, repair open in PWR GND circuit. Remove breakout box, and repeat QUICK TEST. If both resistances are less than 5 ohms, go to next step.

3) Check For Open Between SIG RTN & PWR GND Circuits At ECA Ensure ignition is turned off. With breakout box installed and ECA connected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and test pins No. 40 and 60 at breakout box. If readings are 5 ohms or more, disconnect ECA connector. Inspect connector pins for damage and repair as necessary. If fault is still present, replace ECA and repeat QUICK TEST. If readings are less than 5 ohms, go to step 4).

4) Check Continuity Of SIG RTN Circuit Ensure ignition is turned off. Measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at self-test connector. If resistance is 5 ohms or more, repair open in SIG RTN circuit. Remove breakout box, and repeat QUICK TEST. If reading is less than 5 ohms, go to step 5).

5) Check KAPWR Circuit Voltage At EEC Power Relay Turn ignition off. Locate relay block in engine compartment. Disconnect EEC power relay from relay block. Turn ignition on. Measure voltage between negative battery terminal and KAPWR terminal at EEC power relay connector. If voltage is 10.5 volts or less, check KAPWR circuit between EEC power relay and battery power for open circuit. If voltage is 10.5 volts or more, go to step 6).

6) Check Ignition Circuit Voltage At EEC Power Relay Ensure EEC power relay is disconnected. Turn ignition on. Measure voltage between negative battery terminal and IGNITION terminal at EEC power relay connector. If voltage is less than 10.5 volts, check for open in ignition switch circuits. Repair wiring, and repeat QUICK TEST. If voltage is 10.5 volts or more, go to step 7).

7) Check PWR GND Circuit Continuity Turn ignition off, and wait 10 seconds. With ECA connected to breakout box, measure resistance between negative battery terminal and PWR GND terminal at EEC power relay connector. If resistance is 10 ohms or more, repair open circuit in ground circuit. Repeat QUICK TEST. If reading is less than 10 ohms, go to step 8).

8) Check VPWR Circuit Continuity Turn ignition off. Measure resistance between test pins No. 37 and 57 (VPWR) at breakout box and VPWR terminal of EEC power relay connector. If resistance is 5 ohms or more, repair VPWR open circuit between EEC power relay and ECA. Repeat QUICK TEST. If reading is less than 5 ohms, go to step 9).

9) Check VPWR Circuit Voltage Turn ignition off. Install EEC power relay. Turn ignition on. With ECA connected, measure voltage between test pins No. 37 and 57 (VPWR) and test pins No. 40 and 60 (PWR GND) and 46 (SIG RTN) at breakout box. If voltage is 10.5 volts or more, repair circuit between ECA and EEC power relay. Repeat QUICK TEST. If voltage is less than 10.5 volts, replace EEC power relay. Repeat QUICK TEST.

Perform this test when a check for VREF signal has failed in sensor input CIRCUIT TEST DA and CIRCUIT TEST DS, or if directed by CIRCUIT TEST A or CIRCUIT TEST QA. SIG RTN is a dedicated ground used by most EEC-IV system sensors. VREF is a 5-volt reference voltage that is continuously output by ECA. This consistent voltage signal is used on all 3-wire sensors. This circuit test is only intended to diagnose SIG RTN, VREF, TP, EVP, PFE, DPFE, MAP and BP circuits.

Reference Voltage Circuit & Connector Terminal ID. Scheme 91

CIRCUIT TEST C TEST PIN WIRE COLOR ID

1) Check Battery Power Circuit Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA connected. Turn ignition on. Measure and record voltage between breakout box test pin No. 37 and SIG RTN terminal of self-test connector. Measure and record voltage across battery terminals. If both readings are less than 10.5 volts, or if they differ by more than 1.0 volt, reconnect sensor (if applicable) and go to CIRCUIT TEST B. If voltages are 10.5 volts or more and do not differ from one another by more than one volt, go to step 2).

2) Check VREF Voltage With breakout box installed and ECA connected, set DVOM on 20-volt scale. Turn ignition on. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is 4-6 volts, go to step 3). 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. Measure resistance between test pin No. 26 and VREF terminal at wiring harness connector of applicable sensor. Measure resistance between test pin No. 46 and SIG RTN circuit terminal at wiring harness connector of applicable sensor. If both readings are less than 5 ohms, VREF circuit is okay. If either reading is 5 ohms or more, repair open in VREF or SIG RTN circuit and repeat QUICK TEST.

4) Check For Excess VREF Circuit Voltage Turn ignition off. With breakout box installed, disconnect ECA and scan tester or STAR tester (if applicable). Turn ignition on. Measure voltage between test pin No. 26 and battery ground. If voltage is less than 0.5 volt, replace ECA and repeat QUICK TEST. If voltage is 0.5 volt or more, repair short to battery power in wiring harness. Remove breakout box and repeat QUICK TEST. Replace ECA if fault still occurs.

5) Check For Shorted TPS Turn ignition off. Connect ECA to breakout box. Disconnect Throttle Position Sensor (TPS) from wiring harness. Turn ignition on. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is 4 volts or more, replace TPS and repeat QUICK TEST. If voltage is less than 4 volts on models with EVP, PFE or DPFE sensor, go to step 6); if voltage is less than 4 volts on all other models, go to step 7).

6) Check For Shorted EVP/PFE/DPFE Sensor Turn ignition off. Disconnect EVP/PFE/DPFE sensor. Turn ignition on. Measure voltage between test pins No. 26 and 46. If voltage is 4 volts or more, replace EVP/PFE/DPFE sensor and repeat QUICK TEST. If voltage is less than 4 volts, reconnect EVP/PFE/DPFE sensor and go to step 7).

7) Check For Shorted MAP/BP Sensor On models not equipped with a MAP/BP sensor, go to step 8); on all other vehicles, turn ignition off. Disconnect MAP/BP sensor. Turn ignition on. Measure voltage between test pins No. 26 and 46. If voltage is 4 volts or more, replace MAP/BP sensor. Remove breakout box, and repeat QUICK TEST. If voltage is less than 4 volts, reconnect MAP/BP sensor and go to step 8).

8) Check VREF Circuit For Short To Ground Turn ignition off. Disconnect TPS, MAP/BP sensor and EVP/PFE/DPFE sensor (if equipped). Measure resistance between test pin No. 26 and test pins No. 20, 40, 46 and 60. If any resistance is less than 5 ohms, repair short to ground. Remove breakout box, and repeat QUICK TEST. If original problem still exists, replace ECA and repeat QUICK TEST. If readings are 5 ohms or more, replace ECA and repeat 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 and VAT sensors. 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 up to 15% due to sensor and VREF variations.

This circuit test is intended to diagnose following components and circuits

1. Air Charge Temperature (ACT) sensor.
2. Engine Charge Temperature (ECT) sensor.
3. Wiring harness circuits (ACT, ECT and SIG RTN).
4. Electronic Control Assembly (ECA).

To prevent replacing good components, ensure following non-EEC areas or components are not cause of problem

1. Coolant Level Low
2. Cooling System, Water Pump Or Fan
3. Electro Drive Cooling Fan
4. Engine Operating Temperature Low
5. Engine Oil Level Low
6. Thermostat
7. Air Cleaner Duct
8. Ambient Temperature Too Low

Temperature Sensor Circuit & Connector Terminal ID. Scheme 92

CIRCUIT TEST DA TEST PIN WIRE COLOR ID

1) Code 21/116 Or 24/114 Code 21/116 (ECT) or 24/114 (ACT)indicates corresponding sensor is out of self-test range. Correct range for measurement is .3-3.7 volts. Check for following possible causes

1. Low ambient temperature (less than 50°F).
2. Low coolant level.
3. Faulty harness connector.
4. Faulty sensor.
5. ACT sensor improperly mounted in air cleaner.

If vehicle cannot be started, go to step 3). If vehicle stalls, go to CIRCUIT TEST S. Ensure upper radiator hose is hot and pressurized. Repeat QUICK TEST. If Code 21, 24, 114 or 116 is present, go to step 2). If none of these codes are present, service other codes as necessary.

2) Check VREF Circuit Voltage At TPS Turn ignition off. Disconnect Throttle Position Sensor (TPS). Turn ignition on. Measure voltage at TPS wiring harness connector between VREF and SIG RTN. see scheme 17 If voltage is 4-6 volts, reconnect TPS and go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check Temperature Sensor Resistance Turn ignition off. Disconnect suspect sensor. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. If resistance is not within specification, replace suspected sensor. See ACT & ECT SENSOR SPECIFICATIONS . Reconnect wiring harness, and repeat QUICK TEST. If resistance is within specification, perform following step as applicable.

1. For diagnosing vehicles with ECT sensor and a no-start condition, DO NOT service Code 21/116 at this time. Go to CIRCUIT TEST AA for TFI, CIRCUIT TEST AB for DIS and CIRCUIT TEST AC for EDIS.
2. For other vehicles, go to step 4).

ACT & ECT SENSOR SPECIFICATIONS

4) Warm engine to normal operating temperature. Turn ignition off. Disconnect suspect sensor. Run engine at 2000 RPM for 2 minutes. Measure resistance between sensor signal circuit and SIG RTN circuit at temperature sensor. See ACT & ECT SENSOR SPECIFICATIONS table. If resistance is within specification, replace ECA and repeat QUICK TEST. If sensor is not within specification, replace sensor and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). 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) indicate corresponding sensor signal is greater than self-test maximum. Maximum signal voltage for ECT and ACT sensor is 4.6 volts. Possible causes for excess voltage signals are

1. Open circuit in wiring harness (ACT or ECT).
2. Faulty connection.
3. Faulty sensor.
4. Faulty ECA.

Turn ignition off. Disconnect suspect temperature sensor. Connect a jumper wire between sensor SIG RTN terminal and SIG RTN terminal at temperature sensor wiring harness connector. Repeat QUICK TEST. If Code 61, 64, 112 or 117 is displayed, replace suspect sensor and repeat QUICK TEST. If Code 61, 64, 112 or 117 is not displayed, remove jumper wire and go to next step.

11) Check Continuity Of Sensor Signal & SIG RTN Circuits Turn ignition off. Ensure suspect temperature sensor is disconnected. Disconnect ECA 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance of sensor signal circuit between test pin No. 7 (ECT sensor) or test pin No. 25 (ACT sensor) at breakout box and sensor signal circuit terminal at sensor wiring harness connector. Also measure resistance between test pin No. 46 and SIG RTN circuit at sensor wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST. If either reading is 5 ohms or more, repair open circuit. Remove breakout box and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.

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

1. Circuit grounded in wiring harness (ACT or ECT).
2. Faulty sensor.
3. Faulty ECA.
4. Faulty connection.

Turn ignition off. Disconnect wiring harness connector from suspect sensor. Check for damaged wiring, and repair as necessary. Repeat KOEO SELF-TEST. If Code 51, 54, 113 or 118 is displayed, replace sensor repeat QUICK TEST. If Codes 51, 54, 113 and 118 is not displayed, go to step 21).

21) Check VREF Circuit Voltage At TPS Turn ignition off. Disconnect wiring harness connector from suspect sensor. Disconnect TPS. Turn ignition on. Measure voltage between VREF and SIG RTN at TPS wiring harness connector.If voltage is not 4-6 volts, go to CIRCUIT TEST C. If voltage is 4-6 volts, connect TPS and go to step 22).

22) Check Temperature Sensor Signal For Shorts To Ground Turn ignition off. Disconnect suspect sensor. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 7 (ECT) or 25 (ACT) and pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 51/118, 54/113, 61/117 Or 64/112 A Continuous Memory Code 51/118 or 54/113 indicates sensor signal is greater than self-test maximum of 4.6 volts. Code is set during normal driving conditions. Continuous Memory Code 61/117 or 64/112 indicates sensor signal is less than self-test minimum of 0.2 volt. Code is set during normal driving conditions. Possible causes for these faults are

1. Faulty sensor.
2. Open or grounded circuit in harness.
3. Faulty ECA.

SENSOR CODES

Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe analog voltmeter or scan tester for indication of fault while tapping sensor lightly and wiggling sensor connector. If fault is indicated, disconnect and inspect connector and terminals. If connector and terminals are okay, replace sensor, clear continuous memory and repeat QUICK TEST. If fault is not indicated, go to step 91).

91) Check EEC-IV Wiring Harness While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe analog voltmeter or scan tester while wiggling and bending wiring harness, a small section at a time, from sensor to cowl. Also check harness from cowl to ECA. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and repeat QUICK TEST. If no fault is found, go to step 92).

92) Inspect ECA & Wiring Harness Connectors Turn ignition off. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay and fault cannot be duplicated at this time, see INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 100). No test procedures have been omitted.

100) Continuous Memory Code 338 A Continuous Memory Code 338 indicates cooling system has not reached normal operating temperature. Possible causes for this fault are

1. Thermostat stuck open.
2. Coolant outlet gasket leak.
3. Water pump gasket leak.

Repair cooling system as necessary. Clear continuous memory, and repeat QUICK TEST.

101) Continuous Memory Code 339 A Continuous Memory Code 339 indicates cooling system has overheated. Possible causes for this fault are

1. Coolant level low.
2. Thermostat stuck closed.
3. Coolant system clogged.
4. Radiator fins clogged.
5. Water pump damaged or worn.
6. Radiator cap damaged or worn.
7. Cooling fan damaged or worn.

Repair cooling system as necessary. Clear continuous memory, and repeat QUICK TEST.

Perform this test when directed by QUICK TEST or CIRCUIT TEST S. Barometric pressure sensor output is digital and must be measured using an oscilloscope or MAP/BP tester. To prevent replacement of good components, be aware following non-EEC related areas may be cause of problem

1. Unusually high or low atmospheric barometric pressure.
2. Kinked or blocked vacuum lines.
3. Engine mechanical condition (valves, vacuum leaks, valve timing, EGR valve, etc.).

This test is intended to diagnose following

1. MAP/BP sensor.
2. Wiring harness circuits (VREF, MAP/BP SIG and SIG RTN).
3. MAP vacuum line.
4. ECA.

MAP/BP Sensor Ckt., Connector Terminal & Tester Hookup ID. Scheme 93

CIRCUIT TEST DF TEST PIN WIRE COLOR ID

MAP SENSOR SPECIFICATIONS

MAP/BP SENSOR SPECIFICATIONS

1) Code 22/126: Check Power To MAP/BP Sensor Code 22/126 indicates MAP/BP sensor is out of self-test voltage range (1.4-1.6 volts). Following are possible causes of this code

1. Vacuum trapped at MAP/BP sensor.
2. High atmospheric pressure.
3. MAP/BP signal circuit open between sensor and ECA.
4. MAP/BP signal circuit shorted to VREF, SIG RTN or ground.
5. VREF circuit open at sensor.
6. SIG RTN circuit open at sensor.
7. Faulty MAP/BP sensor.
8. Faulty ECA.

Turn ignition off. Disconnect MAP/BP sensor from wiring harness.Connect MAP/BP tester between wiring harness and MAP/BP sensor. Connect banana plugs of tester into DVOM. Set DVOM on 20-volt scale. Turn ignition on. If Red light or no light is on, VREF is out of range. Go to step 2). If Green light is on, VREF is okay. Go to step 3).

2) Check Power At Sensor Wiring Harness Connector Disconnect MAP/BP sensor. Turn ignition on. If Green light on tester is lit, replace MAP/BP sensor and repeat QUICK TEST. If Green light is not on, remove MAP/BP tester. Connect MAP/BP sensor, and go to CIRCUIT TEST C.

3) Check MAP/BP Sensor Output With MAP/BP tester connected and ignition on, measure sensor output voltage. If output voltage is within range for altitude in which vehicle is being tested, remove MAP/BP tester and go to step 4). If output reading is not within range, remove MAP/BP tester and go to step 5).

If possible, measure output voltage of several known good MAP/BP sensors on available vehicles. Average voltage reading will be typical for location and time of testing.

MAP SENSOR VOLTAGE OUTPUT

4) Check MAP/BP SIG Circuit Continuity Turn ignition off. Disconnect MAP/BP sensor wiring harness connector. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between MAP/BP SIG terminal at sensor wiring harness connector and test pin No. 45. If reading is less than 5 ohms, replace ECA and repeat QUICK TEST. If reading is 5 ohms or more, repair open MAP/BP SIG circuit and repeat QUICK TEST.

5) Check MAP/BP SIG Circuit For Shorts To VREF, SIG RTN & Ground Turn ignition off, and wait 10 seconds. Disconnect ECA60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect wiring harness at MAP/BP sensor. Measure resistance between test pin No. 45 and test pins No. 26, 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short circuit. Repeat QUICK TEST. If all readings are 10,000 ohms or more, replace MAP/BP sensor. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 5) to step 7). No test procedures have been omitted.

7) KOER Code 22/126: Check For EGR-Related Codes Code 22/126 indicates MAP/BP signal is out of self-test range during KOER SELF-TEST. If Code 31, 32, 33, 34, 35, 326, 327, 328, 332, 334, 336 or 337 is present, perform applicable CIRCUIT TEST. See SERVICE CODE REFERENCE CHARTS. If codes are not present, go to step 8).

8) Check MAP Sensor Operation Turn ignition off. Disconnect vacuum hose from MAP sensor. Connect vacuum pump to MAP sensor, and apply 18 in. Hg. If vacuum is not held, replace sensor and repeat QUICK TEST. If MAP sensor holds vacuum, release vacuum and go to step 9).

9) Attempt To Eliminate Code 22/126 Plug MAP sensor vacuum supply hose. Start engine, and run it at 1400-1600 RPM. Slowly apply 15 in. Hg to MAP sensor. Perform KOER SELF-TEST. Check for Code 22/126, disregarding any other codes at this time. If Code 22/126 is still present, replace MAP sensor. If Code 22/126 is not present, inspect MAP sensor vacuum supply hose. If hose is okay, service other codes at this time. If no other code is present, check engine mechanical condition for cause of low vacuum.

10) Code 72/129: Repeat Dynamic Response Test Code 72/129 indicates MAP sensor output did not change enough during dynamic response test. Possible causes for this code are

1. System failed to detect Wide Open Throttle (WOT).
2. Incorrect MAP sensor vacuum hose routing.
3. Faulty MAP sensor.

Repeat KOER SELF-TEST. Ensure complete WOT is performed during dynamic response portion of test. If Code 72/129 is still present, go to step 11). If code is not present, service any other codes as necessary.

11) Code 81/128 Continuous Memory Code 81/128 indicates MAP sensor vacuum has not changed more than 2 in. Hg during normal vehicle operation. Possible causes for this code are

1. MAP sensor vacuum hose is improperly routed, blocked or is leaking.
2. MAP sensor is leaking.

Check vacuum lines for correct routing. Refer to Vehicle Emission Control Identification (VECI) decal. Check for loose connections, kinks and blockage. Repair vacuum lines as necessary. If vacuum lines are okay, go to step 12).

12) Check MAP Sensor Operation Turn ignition off. Disconnect vacuum supply hose from MAP sensor. Attach vacuum pump to MAP sensor. Apply 18 in. Hg to MAP sensor. If MAP sensor holds vacuum, release vacuum and go to step 13). If sensor does not hold vacuum, replace MAP sensor and repeat QUICK TEST.

13) Verify Vacuum To MAP Sensor Decreases During Dynamic Response Test Turn ignition off. Use a "T" fitting to install a vacuum gauge in MAP sensor vacuum hose. Perform KOER SELF-TEST while observing vacuum gauge. If vacuum decreases by more than 10 in. Hg during dynamic response test, replace MAP sensor and repeat QUICK TEST. If vacuum does not decrease by more than 10 in. Hg, EEC-IV system is okay. Check for engine mechanical problems affecting engine vacuum.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 90). No test procedures have been omitted.

90) Code 22/126 Continuous Memory Code 22/126 indicates MAP/BP sensor was out of self-test range (1.4-1.6 volts) during normal driving conditions. Possible causes for this code are

1. Faulty MAP/BP sensor.
2. Faulty wiring harness or connectors.
3. Unusually high or low barometric pressure.

Enter CONTINUOUS MONITOR MODE (WIGGLE TEST). Observe test equipment while performing following

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

If a fault is indicated, disconnect sensor and inspect connectors. Repair if necessary. If connectors are okay, replace MAP/BP sensor. Repeat QUICK TEST. If a fault is not indicated, go to step 91).

91) Check EEC-IV Wiring Harness Stay in wiggle test. Observe analog VOM or scan tester for indication of fault while bending or wiggling small sections of harness from sensor connector to firewall and from firewall to ECA. If fault is indicated, isolate fault in harness and repair as necessary. Repeat QUICK TEST. If no fault is indicated, go to step 92).

92) Check ECA & Wiring Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connectors and terminals for damage. Repair if necessary. If connectors and terminals are okay, fault cannot be duplicated at this time. Testing is complete. Refer to INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Perform this test when Code 25/225 is retrieved during QUICK TEST procedure or if directed by other diagnostic tests. This test is intended to diagnose

1. Knock sensor.
2. Wiring harness circuits (KS and SIG RTN).
3. ECA.

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

1. Poor fuel quality.
2. Engine mechanical condition.
3. Ignition timing.

Knock Sensor Circuit & Connector Terminal ID. Scheme 94

CIRCUIT TEST DG TEST PIN WIRE COLOR ID

1) Code 25/225: Generate Knock Signal Manually Code 25/225 indicates Knock Sensor (KS) signal was not received by ECA during dynamic response (goose) check in KOER SELF-TEST. Possible causes for this fault are

1. Faulty Knock Sensor (KS).
2. Open or shorted harness.
3. Faulty ECA.

Have 4-oz. hammer ready. Ensure engine is at normal operating temperature. Perform KOER SELF-TEST. Immediately after dynamic response check request signal appears, lightly tap above knock sensor using 4-oz. hammer. DO NOT goose throttle. Check for Code 25/225. Ignore all other codes at this time. If Code 25/225 is not displayed, knock system is okay. Repeat KOER SELF-TEST, and service any other codes. If Code 25/225 is displayed, go to step 2).

2) Check KS Circuit Voltage Turn ignition off. Disconnect knock sensor. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between KS and SIG RTN terminals at sensor wiring harness connector. If reading is less than one volt, go to step 3). If voltage is 4 volts or more, go to step 5). If reading is 1-4 volts, go to step 6).

3) Check Continuity Of KS & SIG RTN Circuits Turn ignition off. Disconnect ECA 60-pin connector. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA and knock sensor disconnected. Measure resistance between SIG RTN terminal at KS wiring harness connector and test pin No. 46 at breakout box. Measure resistance between KS terminal at wiring harness connector and test pin No. 23 at breakout box. If either reading is 5 ohms or more, repair open circuit. Repeat QUICK TEST. If both readings are less than 5 ohms, go to step 4).

4) Check KS Circuit For Short To Ground Turn ignition off. Measure resistance between test pin No. 23 and test pins No. 40, 46 and 60 at breakout box. If all readings are 10,000 ohms or more, remove breakout box. Reconnect ECA, and go to step 6). If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, and repeat QUICK TEST.

5) Check KS Circuit For Short To Voltage Turn ignition on. Measure voltage between test pins No. 23 and 40. If reading is 0.5 volt or more, repair knock sensor harness short to power. Remove breakout box, and repeat QUICK TEST. If reading is less than 0.5 volt, remove breakout box. Connect ECA, and go to step 6).

6) Test ECA Using Substitute Knock Sensor Turn ignition off. Connect substitute knock sensor into harness but do not install sensor on engine. Ensure engine is at normal operating temperature. Perform KOER SELF-TEST. When dynamic response check signal appears, lightly tap knock sensor using 4-oz. hammer. DO NOT goose throttle. If Code 25/225 is displayed, replace ECA. Connect original knock sensor, and repeat QUICK TEST. If Code 25/225 does not appear, install new knock sensor and repeat QUICK TEST.

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

1. Throttle Position Sensor (TPS).
2. Wiring harness circuits (TP, SIG RTN and VREF).
3. ECA.

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

1. Idle speed.
2. Binding throttle shaft or linkage.
3. Throttle stop adjustment.
4. Throttle Position Sensor (TPS) not seated.

TPS Circuits & Connector Terminal ID. Scheme 95

CIRCUIT TEST DH TEST PIN WIRE COLOR ID

TPS Specification Chart. Scheme 96

1) Code 23/121: Check For Other Codes Code 23/121 indicates TPS rotational setting may be out of self-test range. Possible causes for this fault are

1. Binding throttle linkage.
2. TPS not seated correctly.
3. Faulty TPS.
4. Faulty ECA.

Perform KOER SELF-TEST. Check for Code 31/327. If either of these codes are present with Code 23/121, service Code 31/327 and repeat QUICK TEST. If these codes are not present, go to step 2).

2) Code 23/121: Check For Binding Throttle Plate Inspect throttle body and linkage for binding. If throttle plate is binding, check for binding throttle or cruise control linkage, vacuum line or harness interference, etc. Repair as necessary, and repeat QUICK TEST. If no mechanical problem is found, go to step 3).

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

1. TPS not seated properly.
2. Faulty TPS.
3. VREF circuit shorted in wiring harness.
4. Faulty ECA.

Turn ignition off. Disconnect TPS wiring harness connector. Inspect and repair connector pins if damaged. Repeat KOEO SELF-TEST. Ignore all other codes at this time. If Code 63/122 is not displayed, go to step 5). If Code 63/122 is displayed, go to step 4).

4) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. If reading is 4-6 volts, replace TPS and repeat QUICK TEST. If reading is not 4-6 volts, reconnect sensor and go to CIRCUIT TEST C.

5) Check TP Circuit For Short To Power Turn ignition off. Disconnect TPS from wiring harness. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 47 and test pins No. 26 and 57. If either resistance is less than 10,000 ohms, repair short circuit in wiring harness and repeat QUICK TEST. If both resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 5) to step 10). No test procedures have been omitted.

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

1. TPS not seated correctly.
2. Faulty TPS.
3. Open circuit in wiring harness.
4. Grounded circuit in wiring harness.
5. Faulty ECA.

Turn ignition off, and wait 10 seconds. Disconnect TPS from harness. Install a jumper wire between VREF and TP terminals at TPS wiring harness connector. Perform KOEO SELF-TEST. If either Code 53/123 or 23/121 is present, replace TPS and repeat QUICK TEST. If Codes 53/123 and 23/121 are not present, remove jumper wire and go to step 11). If any other codes are present, ignore at this time. If no codes are present, remove jumper wire and go to step 13).

11) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. If voltage is not 4-6 volts, reconnect all components and go to CIRCUIT TEST C. If voltage is 4-6 volts, go to step 12).

12) Check TPS Circuit Continuity Turn ignition off. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between TP terminal at TPS wiring harness connector and test pin No. 47. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to step 13).

13) Check TP Circuit For Shorts To Ground Turn ignition off. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Measure resistance between test pin No. 47 and test pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.

20) KOER Code 73/167: Repeat Dynamic Response Test KOER Code 73/167 indicates TPS did not exceed 25% rotation during dynamic response portion of KOER SELF-TEST. A complete Wide Open Throttle (WOT) must be performed during dynamic response portion of test. Perform KOER SELF-TEST. Ensure WOT is obtained during dynamic response portion of test. If Code 73/167 is still present, go to step 21). If code is not present, system is unable to duplicate Code 73/167 at this time. Service any other KOER codes. If no other service codes are present, testing is complete.

21) Check TPS Movement During Dynamic Response Test Turn ignition off. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. Connect DVOM between test pins No. 46 and 47 at breakout box. Perform KOER SELF-TEST. Ensure a WOT is obtained during dynamic response portion of test. If DVOM reading exceeds 3.5 volts, replace ECA and repeat QUICK TEST. If reading does not exceed 3.5 volts, ensure TPS is correctly installed and adjusted. If TPS is correctly installed and adjusted, replace TPS. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 53/123 This test monitors TPS under simulated road conditions. Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Fully open throttle while observing DVOM or diagnostic tester for indication of fault. Slowly bring throttle to closed position. Lightly tap TPS and wiggle harness connector. If no fault is indicated, go to step 92). If fault is indicated, go to step 91).

91) Measure TP Circuit Voltage While Exercising TPS Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect it for damaged wiring, and repair if necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. Stay in wiggle test (as in previous step). Connect DVOM between test pins No. 47 and 46. Set DVOM on 20-volt scale. Turn ignition on. Observe DVOM and repeat step 90). If fault occurs at less than 4.25 volts, inspect TPS connectors and terminals. If connectors and terminals are okay, replace TPS and repeat QUICK TEST. If fault does not occur at less than 4.25 volts, TPS over-travel may have caused Continuous Memory Code 53/123. TPS is okay. Go to step 92) to check wiring harness.

92) Check EEC-IV Wiring Harness While in wiggle test, bend and shake small sections of EEC-IV harness from TPS connector to firewall and from firewall to ECA while observing analog voltmeter or scan tester. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes, and repeat QUICK TEST. If no fault is indicated, go to next step.

93) Check ECA & Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector from breakout box and inspect for damage. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 53/123 testing is complete. If connector or terminals are damaged, repair as necessary. Clear codes from ECA memory, and repeat QUICK TEST.

94) Continuous Memory Code 63/122 This test checks for open or short circuit in TPS and wiring harness under simulated road conditions. Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe VOM or diagnostic tester for indication of fault while performing following

1. Fully open throttle to WOT.
2. Slowly bring throttle to closed position.
3. Lightly tap TPS and wiggle connector.

If fault is indicated, disconnect TPS. Inspect connectors and terminals. If connectors and terminals are okay, replace TPS. Clear codes from ECA memory, and repeat QUICK TEST. If no fault is indicated, go to next step.

95) Check EEC-IV Wiring Harness Stay in wiggle test (as in previous step). Bend, wiggle and shake small sections of EEC-IV harness from TPS wiring harness connector to firewall and from firewall to ECA while observing analog voltmeter or scan tester. If fault is indicated, isolate fault in wiring and repair as necessary and repeat QUICK TEST. If no fault is indicated, go to step 96).

96) Check ECA & Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connectors and terminals for damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 63/122 testing is complete.

Perform this test when instructed by QUICK TEST or if directed by other test procedures. To prevent replacement of good components, be aware a damaged EGR valve may be cause of problem. This CIRCUIT TEST is intended to diagnose the following

1. EVP Sensor
2. EVR Solenoid
3. EGR Valve Assembly
4. ECA
5. EGR And EVR Vacuum Lines
6. VREF, EVP, SIG RTN, EVR And VPWR Harness Circuits

EVR solenoid receives variable input from ECA, which allows it to control vacuum level to EGR valve. Vacuum not used by EGR is routed to EVR solenoid and vented to atmosphere.

EVP Sensor & EVR Solenoid Circuit & Connector ID. Scheme 97

CIRCUIT TEST DN TEST PIN WIRE COLOR ID

Note. EVR sensor is preloaded when attached to EGR valve. Valve failure causing EVR sensor to lose preload may set Code 31/327.

1) Code 31/327: Generate Code 35/337 Code 31/327 indicates EVP sensor signal is less than self-test minimum of 0.2 volt. Possible causes for this fault are

1. Faulty EVP sensor.
2. Open or grounded harness.
3. Faulty ECA.

Turn ignition off. Disconnect EVP wiring harness connector at sensor. Install a jumper wire between VREF terminal and EVP terminal at EVP sensor wiring harness connector. Repeat KOEO SELF-TEST and KOER SELF-TEST. Check for Code 337. Ignore all other codes at this time. If Code 35/337 is present, replace EVP sensor and repeat QUICK TEST. If Code 35/337 is not present, remove jumper wire and go to step 2).

2) Check VREF Circuit Voltage Disconnect EVP sensor. Turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at EVP sensor wiring harness connector. If voltage is 4-6 volts, go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check EVP Circuit Resistance Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV)leaving ECA disconnected. Measure resistance between EVP terminal at EVP sensor wiring harness connector and test pin No. 27. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to step 4).

4) Check EVP Circuit For Shorts To Ground With ignition off and EVP sensor disconnected, measure resistance between test pin No. 27 and test pins No. 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace ECA and repeat QUICK TEST.

5) Code 35/337: Generate Code 31/327 Code 35/337 indicates EVP sensor signal is greater than self-test maximum of 4.81 volts. Possible causes for this fault are

1. Faulty EVP sensor.
2. Faulty ECA.
3. Short to power in vehicle harness.

Turn ignition off. Disconnect EVP sensor. Perform KOEO SELF-TEST and KOER SELF-TEST. Check for Code 31/327. Ignore all other codes at this time. If Code 31/327 is present, go to step 6). If Code 31/327 is not present, go to step 7).

6) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at EVP sensor wiring harness connector. If reading is 4-6 volts, replace EVP sensor. Repeat QUICK TEST. If reading is not 4-6 volts, go to CIRCUIT TEST C.

7) Check EVP Circuit For Short To Power Turn ignition off. Inspect ECA 60-pin connector terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 27 and test pins No. 26 and 57 at breakout box. If either reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If both readings are 10,000 ohms or more, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 10). No test procedures have been omitted.

10) Code 84/558: Check EVR Solenoid Resistance Code 84/558 indicates fault in EVR solenoid circuit. Possible causes for this fault are

1. Faulty EVR solenoid.
2. Faulty ECA.
3. Shorted or open harness.

Turn ignition off. Disconnect EVR solenoid connector. Measure resistance across EVR solenoid terminals. If reading is not within specification, replace EVR solenoid assembly and repeat QUICK TEST. See EVR SOLENOID RESISTANC . If reading is within specification, go to step 11).

EVR SOLENOID RESISTANCE

11) Check VPWR Circuit Voltage Turn ignition on. Measure voltage between negative battery terminal and VPWR terminal at EVR solenoid wiring harness connector. If reading is less than 10.5 volts, repair open in VPWR circuit and repeat QUICK TEST. If reading is 10.5 volts or more, go to step 12).

12) Check EVR Circuit Continuity Turn ignition off. Disconnect EVR solenoid. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between EVR terminal at EVR solenoid wiring harness connector and test pin No. 33. If reading is less than 5 ohms, go to next step. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

13) Check EVR Circuit For Shorts To Power Or Ground Turn ignition off. Measure resistance between test pin No. 33 and pins No. 37, 40, 46, 57 and 60 at breakout box. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If code is repeated, replace ECA. If all readings are 10,000 ohms or more, replace ECA. Remove breakout box, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.

20) Code 34/334: Check For Code 84/558 Code 34/334 indicates EGR valve and/or EVP is not fully seated in closed position. EVP voltage signal, in closed position, is greater than self-test maximum of 0.67 volt. Because of EVP sensor preload, determining whether EGR valve is seated or EVP sensor contacts EGR valve stem is difficult. Possible causes for this fault are

1. Poor contact in EVP sensor circuit.
2. EGR valve not seated.
3. Faulty EGR valve.
4. Faulty EVP sensor.
5. Faulty EVP solenoid.
6. Faulty ECA.

Turn ignition off. Perform KOEO SELF-TEST. If Code 84/558 is present, return to step 10). If Code 84/558 is not present, go to step 21).

21) Perform SELF-TEST Without EGR Remove and plug vacuum line to EGR valve. Perform KOEO SELF-TEST and KOER SELF-TEST. If Code 34/334 is still present, go to step 22). If Code 34/334 is not present, check EVR solenoid for obstructions. Replace EVR solenoid if no obstructions are present.

22) Check EGR Valve & EVP Sensor Operation Turn ignition off.Disconnect EVP sensor. Inspect harness and connector. Service if necessary. Remove and plug vacuum hose to EGR valve. Install vacuum gauge at EGR valve vacuum hose. Operate EGR valve by applying and releasing vacuum. Install vacuum hose to EGR valve. Repeat KOEO SELF-TEST and KOER SELF-TEST. If Code 34/334 is present, go to step 23). If Code 34/334 is not present, original fault was caused by poor continuity at EVP sensor connector or binding **of EGR valve stem.

23) Check EVP Signal Voltage Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between test pin No. 27 and test pin No. 46 at breakout box. If voltage is less than 0.67 volt, replace ECA and repeat QUICK TEST. If voltage is greater than 0.67 volt, go to step 24).

24) EGR Valve/EVP Sensor Fault Isolation Remove EGR valve and EVP sensor. Inspect valve and sensor for binding, carbon deposits, excessive wear and damage. Repair or replace as necessary. Install EGR valve and EVP sensor. Perform KOEO SELF-TEST and KOER SELF-TEST. If Code 34/334 is still present, replace EGR valve. If Code 34/334 is not present, testing is complete.

25) Service Code 32/328 Service Code 32/328 indicates EVP sensor is lower than normal (0.24 volt) in closed position. Possible causes for this fault are

1. Faulty EGR valve.
2. Faulty EVP sensor.
3. Faulty ECA.
4. Open or shorted EVP sensor.

Turn ignition off. Disconnect EVP sensor. Inspect harness and connector, and service as necessary. Remove and plug vacuum hose to EGR valve. Install vacuum gauge at EGR valve vacuum hose. Operate EGR valve by applying and releasing vacuum. Install vacuum hose to EGR valve. Repeat KOEO SELF-TEST and KOER SELF-TEST. If Code 32/328 is not present, original fault was caused by poor continuity at EVP sensor connector or binding/sticking of EGR valve stem. If Code 32/328 is present, go to step 26).

26) Check EVP Signal Voltage Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Remove and plug vacuum hose to EGR valve. Install vacuum gauge at EGR valve vacuum hose. Turn ignition on. Measure voltage between test pin No. 27 and test pin No. 46 at breakout box while performing following: apply 6 in. Hg to EGR valve and slowly bleed vacuum completely off. If voltage drops to less than 0.24 volt, replace ECA and repeat QUICK TEST. If voltage remains more than 0.24 volt, go to step 27).

27) Substitute EVP Sensor On Original EGR Valve Turn ignition off. Install a known good EVP sensor on original EGR valve. Ensure all hoses and electrical connectors are attached. Perform KOEO SELF-TEST and KOER SELF-TEST. If Code 32/328 is present, check EGR valve for mechanical malfunction. If Code 32/328 is not present, replace original EVP sensor. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 27) to step 40). No test procedures have been omitted.

40) KOER Code 33/332: Check Vacuum At EGR KOER Code 33/332 indicates EVP sensor input did not change after ECA signaled operation of EGR. Because Code 84/558 was not retrieved in KOEO SELF-TEST, EVR solenoid electrical function is okay. Lack of Code 32/328 or 34/334 indicates EVP sensor is within closed position specifications. Possible causes for this fault are

1. Leaking vacuum hose.
2. Restricted vacuum hose.
3. Restricted EVR solenoid.
4. Faulty EGR valve.

Turn ignition off. Disconnect vacuum line from EGR valve. Connect a vacuum gauge at open end of line. Perform KOER SELF-TEST while observing vacuum gauge. If vacuum reading is more than 1.0 in. Hg, remove vacuum gauge and go to step 43). If reading is 1.0 in. Hg or less, go to step 41).

41) Verify Vacuum Supply To EVR Solenoid Turn ignition off. Disconnect vacuum hose to EVR solenoid at source. Install vacuum gauge at source. Start engine and check vacuum. If reading is 10 in. Hg or more, go to step 42). If reading is less than 10 in. Hg, check vacuum line to EVR solenoid. Repair if necessary. Repeat QUICK TEST.

42) Check Vacuum Between EVR Solenoid & EGR Valve Carefully check vacuum hose for cracks, loose connections, blockage and kinks. Repair or replace vacuum hose if necessary, and repeat QUICK TEST. If vacuum hose is okay, check EVR solenoid filter for obstructions. Replace if necessary. If filter is okay, replace EVR solenoid. After repairs are made, repeat QUICK TEST.

43) Check EVP Sensor & EGR Valve Operation Turn ignition off.Disconnect EVP sensor. Inspect connector and harness for damage, and service as necessary. Remove and plug vacuum hose from EGR valve. Connect vacuum pump to EGR valve. Test EGR valve operation by applying and releasing vacuum. Connect vacuum line to EGR valve. Connect wiring harness connector to EVP sensor. Repeat KOER SELF-TEST. If Code 33/332 is still present, go to step 44). If Code 33/332 is not present, original code was set either by poor continuity at EVP sensor connector or sticking EGR valve. Test is complete.

44) Verify EGR Valve Vacuum Control Turn ignition off. Install tachometer. Remove idle air by-pass wiring harness connector. Remove and plug vacuum hose from EGR valve. Start engine, and allow it to idle with transmission in Neutral. Ensure idle speed is adjusted correctly. Connect vacuum pump to EGR valve. Slowly apply 5-10 in. Hg. If vacuum drops more than 100 RPM with vacuum applied and returns to correct idle with vacuum released, replace EVP sensor. If vacuum does not drop more than 100 RPM with vacuum applied, repair or replace EGR valve.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 44) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 31/327, 32/328 Or 35/337 Continuous Memory Code 31/327 or 32/328 indicates EGR valve closed further than normal or EVP circuit failed with intermittent low voltage sometime during engine operation. Code 35/337 indicates EVP signal to ECA was above maximum self-test limit sometime during engine operation. Possible causes for these faults are

1. Obstructed vacuum valve.
2. Faulty EVP sensor.
3. EGR valve.

Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Connect DVOM between test pins No. 27 and 46 at breakout box. Wiggle wiring harness and lightly tap on EVP sensor. If voltage remains steady at .24-.67 volt, go to step 91). If voltage is erratic or not within .24-.67 volt range, remove and inspect EVP sensor wiring harness connector. Repair or replace if necessary. If sensor connector is okay, replace EVP sensor.

91) Check Wiring Harness Connect DVOM between test pins No. 27 and 46 at breakout box. Turn ignition on. Observe DVOM for fault indication while wiggling and bending small sections of wiring harness near sensor, working from sensor toward firewall. Wiggle and bend wiring harness from firewall to ECA. If fault is indicated, isolate fault and repair wiring harness. Clear codes, and repeat QUICK TEST. If fault is not found, go to step 92).

92) Measure EVP Signal Voltage While Exercising EVP Sensor Remove and plug vacuum hose to EGR valve. Install vacuum gauge at EGR valve vacuum hose. Turn ignition on. Measure voltage between test pin No. 27 and test pin No. 46 at breakout box while performing following: apply 5-10 in. Hg to EGR valve and slowly bleed vacuum completely off. If voltage steadily fluctuates between 0.24-4.81 volts, problem is intermittent and cannot be duplicated at this time. If voltage does not fluctuate between 0.24-4.81 volts, replace EVP sensor and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 110). No test procedures have been omitted.

110) Continuous Memory Code 33/332 Code 33/332 indicates EGR valve did not open with engine at normal operating temperature and with EVR solenoid signal present sometime during engine operation. Possible causes of this fault are

1. Fault in vacuum line.
2. Faulty EGR valve.
3. Open or shorted EVR circuit.

Turn ignition off. Disconnect vacuum hose at EGR valve. Connect vacuum pump to valve. Apply 10-20 in. Hg to EGR valve. If EGR valve opens and holds vacuum, go to step 111). If EGR valve does not open and hold vacuum, service or replace EGR valve as necessary and repeat QUICK TEST.

111) EVR Solenoid & Wiring Harness Check Turn ignition off. Disconnect vacuum hose from EGR valve. Connect EGR valve hose to vacuum gauge. Disconnect ECA 60-pin connector. Inspect for damaged terminals and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Start engine, and allow it to idle. Connect jumper wire between test pins No. 33 and 40. Tap on EVR sensor and wiggle wiring harness while observing vacuum gauge. If vacuum gauge shows a sudden drop in vacuum, isolate cause and repair as necessary. If vacuum gauge does not show a drop in vacuum, problem is intermittent and cannot be duplicated at this time.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 111) to step 115). No test procedures have been omitted.

115) Continuous Memory Code 34/334: Code 34/334 indicates EGR valve was open with engine idling at normal operating temperature. Possible causes for this fault are

1. Faulty EVR sensor.
2. Faulty EVR solenoid.
3. Faulty EGR valve.

Turn ignition off. Disconnect vacuum hose from EGR valve. Connect EGR valve hose to vacuum gauge. Start engine, and allow it to idle. Tap on EVR sensor and wiggle wiring harness while observing vacuum gauge. If vacuum gauge reading does not remain below 1.0 in. Hg and/or has sudden vacuum increase, service or replace EVR solenoid. If vacuum gauge reading remains below 1.0 in. Hg with no sudden increase, go to step 116).

116) EVR Solenoid Check Leave engine idling and vacuum gauge connected to EGR valve hose. Observe vacuum gauge while wiggling and bending small sections of wiring harness near EVR sensor, working from sensor toward firewall. Wiggle and bend wiring harness from firewall to ECA. If vacuum gauge shows an increase in vacuum, isolate cause and repair as necessary. If vacuum gauge does not show an increase in vacuum, go to step 117).

117) Check EVR Signal At ECA Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV).Connect ECA to breakout box. Start engine, and allow it to idle. Connect DVOM between test pins No. 27 and 46 at breakout box. Wiggle wiring harness and lightly tap on EVP sensor. If voltage increases to more than 0.67 volt, remove and service EGR valve. If voltage is still more than 0.67 volt, replace EVP sensor. If voltage is 0.67 volt or less, problem is intermittent and cannot be duplicated at this time.

FIPL Connector & Circuits. Scheme 98

Enter this CIRCUIT TEST only when instructed during QUICK TEST. If you were directed here from KOEO Code 23 but an engine ID code of 5.0 was not received, go to CIRCUIT TEST DJ.

1) Service Code 23: Throttle Linkage Check Inspect throttle linkage for binding, sticking or interference. If throttle linkage does not operate smoothly, service as necessary and repeat QUICK TEST. If throttle does operate smoothly, go to next step.

2) Service Code 53: Attempt to Generate Code 63 With ignition off, and FIPL disconnected, inspect and repair any corroded or damaged pins. Perform KOEO self test. If Code 63 is present, go to next step. If code 63 is not present, go to step 4).

3) VREF Circuit Voltage Check With ignition off and FIPL disconnected, measure voltage at SIG RTN and VREF circuit at connector. If voltage is not 4.0-6.0 volts, connect all components and go to CIRCUIT TEST C, step 1). If voltage is 4.0-6.0 volts, connect all components and go to step 14).

4) Check for Shorts to Power With ignition off and FIPL disconnected, install breakout box leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 47 and test pins No. 26 and 57. If resistance is 10,000 ohms or more, replace ECA; remove breakout box and reconnect components. Repeat QUICK TEST. If resistance is less than 10,000 ohms, repair short circuit; remove breakout box and reconnect all components. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.

10) Service Code 63: Attempt to Generate Code 53/23 With ignition off, disconnect FIPL wiring harness connector. Inspect connector and harness for damage, and service as necessary. Connect jumper wire between VREF and TP circuit at FIPL wiring harness connector. Perform KOEO SELF TEST. If no codes are present, go to step 13). If Codes 23 or 53 are present, remove jumper wire and go to step 14). If Codes 23 or 53 are not present, go to next step.

11) VREF Circuit Voltage Check With ignition off and FIPL disconnected, measure voltage at SIG RTN and VREF circuit at connector. If voltage is not 4.0-6.0 volts, connect all components and go to CIRCUIT TEST C, step 1). If voltage is 4.0-6.0 volts, connect all components and go to step 12).

12) FIPL Circuit Continuity Check With ignition off and FIPL disconnected, install breakout box leaving ECA connected. Inspect connector and harness for damage, and service as necessary. Measure resistance between test pin No. 47 and TP circuit at FIPL wiring harness connector. If resistance is 5 ohms or more, repair open circuit; remove breakout box and reconnect components. Repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

13) Check for Shorts to Ground With ignition off and FIPL disconnected, install breakout box leaving ECA disconnected. Inspect connector and harness for damage, and service as necessary. 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 resistance is 10,000 ohms or more, replace ECA; remove breakout box and reconnect components. Repeat QUICK TEST. If resistance is less than 10,000 ohms, repair short circuit; remove breakout box and reconnect all components. Repeat QUICK TEST.

Note. Super STAR II scan tester is required for FIPL adjustment.

14) FIPL Sensor Adjustment Perform KOEO SELF-TEST while holding throttle fully open. After last service code has been received, remain in self-test. Place 0.515" gauge between FIPL travel screw and gauge boss. Cycle overdrive cancel switch. Observe Super STAR II tester for one of the following modes

1. Constant tone, solid light or consistent STO LO readout indicates FIPL sensor is within range. Cycle overdrive cancel switch to exit test.
2. Beeping tone, flashing light or erratic STO readout indicates adjustment is required.
3. If tone is undetectable, FIPL sensor may be worn.
4. If adjustment is required, loosen adjusting screws and rotate sensor until a constant tone, solid light or consistent STO LO readout appears. Tighten adjusting screws, and remove gauge block. Repeat QUICK TEST. If service codes are still present or constant tone cannot be obtained, replace FIPL sensor.

Adjusting FIPL Sensor. Scheme 99

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 53: Monitor FIPL Circuit Under Simulated Road Conditions Enter KOEO wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe DVOM or diagnostic tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position, and lightly tap FIPL and wiggle harness connector. This test checks for open or short in FIPL, connectors and wiring harness. If no fault is indicated, go to step 92). If fault is indicated, go to step 91).

91) Measure TP Circuit Voltage While Exercising FIPL Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Install EEC-IV Breakout Box (T83L-50-EEC-IV) leaving ECA connected. Stay in KOEO wiggle test (as in previous step). Connect DVOM between test pins No. 46 and 47. Turn ignition on. Observe DVOM and repeat step 90). If fault occurs at less than 4.25 volts, inspect FIPL connectors and terminals. If connectors and terminals are okay, go to step 14). If fault does not occur at less than 4.25 volts, go to step 92).

92) Check EEC-IV Vehicle Harness While in KOEO wiggle test, shake, bend and wiggle small sections of EEC-IV harness from FIPL vehicle harness connector to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to step 93).

93) Check ECA & Harness Connectors Turn ignition off. Inspect ECA 60-pin connector and terminal for damage. Repair as necessary. Clear Continuous Memory Codes and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Testing is complete.

94) Continuous Memory Code 63: Monitor TP Circuit Under Simulated Road Conditions Enter KOEO wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Check VOM or diagnostic tester for fault while performing the following

1. Slowly open throttle to WOT.
2. Slowly bring throttle to closed position.
3. Lightly tap FIPL and wiggle connector.

This test checks for open or short in FIPL, connectors and vehicle harness. If fault is indicated, disconnect FIPL. Inspect connector and terminal. If connector and terminals are okay, go to step 14). If no fault is indicated, go to step 95).

95) Check EEC-IV Vehicle Harness While in KOEO wiggle test (CONTINUOUS MONITOR MODE), shake, bend and wiggle small sections of EEC-IV harness from FIPL vehicle harness connector to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Clear Continuous Memory Codes and repeat QUICK TEST. If no fault is indicated, go to step 96).

96) Check ECA and Harness Connectors Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector and terminal for damage. Repair as necessary. Clear Continuous Memory Codes and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 63/122 testing is complete.

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

1. PSOM output to ECA.
2. PSOM (+) and PSOM (-) wiring harness circuits.
3. ECA.

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

1. Cruise control system.
2. Rear anti-lock brake system.
3. Instrumentation system.

Programmable Speedometer/Odometer Module (PSOM) Circuit. Scheme 100

Programmable Speedometer/Odometer Module (PSOM) Connector Terminal ID. Scheme 101

CIRCUIT TEST DS TEST PIN WIRE COLOR ID

Note. A failure in the combination 2 wire Vehicle Speed Sensor may cause a Code 452.

1) Continuous Memory Code 29/452 Code 29/452 indicates ECA detected incorrect output from VSS sometime during vehicle operation. Following are possible causes of code.

1. PSOM Output To ECA
2. PSOM (+) And PSOM (-) Wiring Harness Circuits
3. ECA

Turn ignition off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pins No. 3and 6 at breakout box. If reading is 21,000-55,000 ohms, go to step 4). If resistance is not 21,000-55,000 ohms, go to step 2).

2) Check PSOM Circuit Continuity Ensure ignition is off. Disconnect PSOM wiring harness connector. Measure resistance between test pin No. 3 at breakout box and PSOM + circuit at PSOM wiring harness connector. If resistance is less than 5 ohms, repair open circuit and repeat QUICK TEST. If resistance is more than 5 ohms, go to step 3).

3) Check PSOM Circuit For Open Ensure ignition is off. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If resistance is 10,000 ohms or less, repair open circuit and repeat QUICK TEST. If resistance is more than 10,000 ohms, go to step 4).

4) Turn ignition off. Connect ECA to breakout box. Connect wiring harness connector to PSOM. Set DVOM on 20-volt AC scale. Start engine, and warm it to normal operating temperature. Measure voltage between test pins No. 3 and 6 while gradually increasing vehicle speed to 50 MPH. If maximum voltage is less than 4.5 volts, fault is in instrument cluster. If maximum voltage received is more than 4.5 volts, replace ECA.

Perform this test when directed by QUICK TEST. This test is intended to diagnose a faulty BOO switch circuit or ECA. To prevent replacement of good components, be aware following non-EEC related areas may be at fault

1. Brakelight bulb.
2. Brakelight switch or brakelight fuse.

BOO Switch Circuit. Scheme 102

TEST PIN 2 (BOO) WIRE COLOR ID

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

1. Brake pedal not depressed during self-test.
2. Brake pedal pressed during entire self-test.
3. Open brakelight circuit.
4. Short to ground or power.
5. Faulty ECA.

If brake was not depressed during KOER SELF-TEST, repeat test. Depress and release brake pedal only once during test. If pedal was depressed, go to step 2).

2) Check Operation Of Brakelights With ignition on, check operation of brakelights. If brakelights operate normally, go to step 3). If brakelights do not operate, go to step 4). If brakelights are always on,go to step 5).

3) Check For BOO Switch Circuit Cycling Turn ignition off. Wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pins No. 2 and 40 while applying and releasing brake. If voltage cycles, replace ECA and repeat QUICK TEST. If voltage does not cycle, repair open circuit in BOO switch circuit between ECA and BOO switch connection to brakelight circuit. Repeat 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 ground. If voltage is greater than 10 volts, check condition of brakelight switch. If brakelight switch is okay, repair open circuit between brakelight switch and brakelight ground. Repeat QUICK TEST. If voltage is less than 10 volts, repair open BATT (+) circuit to brakelight switch and repeat QUICK TEST.

5) Verify Brake Switch Is Not Always Closed Turn ignition off. Disconnect brakelight switch (located on brake pedal). Turn ignition on. If brakelights are still on, go to step 6). If brakelights are not on, verify correct installation of brakelight switch. If installation is okay, replace brakelight switch and repeat QUICK TEST.

6) Check For Short To Power In ECA Turn ignition off. Disconnect ECA. Turn ignition on, and check brakelights. If brakelights are on, repair short to power between ECA and harness connector and repeat QUICK TEST. If brakelights are not on, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 6) to step 10). No test procedures have been omitted.

10) Code 75/531 Code 75/531 indicates that while brake pedal was released during KOER SELF-TEST, BOO switch signal was high. Possible causes for this fault are

1. Brake pedal depressed during entire self-test.
2. Open BOO switch/brakelight circuit (between ECA and brakelight ground).
3. Short to POWER.
4. Faulty brakelight switch.
5. Faulty ECA.

Turn ignition on. Check brakelight operation. If brakelights operate normally, go to step 11). If brakelights are always on, go to step 5). If brakelights are off, inspect brakelight bulbs. If bulb is okay, repair open circuit between BOO switch connection to brakelight circuit and brakelight ground.

11) Check Continuity Of BOO Switch Circuit Turn ignition off. Disconnect brakelight switch (located on brake pedal). Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 2 at breakout box and BOO switch terminal at switch wiring harness connector. If resistance is less than 5 ohms, replace ECA and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit between ECA and BOO switch connection to brakelight circuit and repeat KOER SELF-TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 536 Code 536 indicates a BOO switch circuit failure. If BOO switch input does not cycle after a predetermined number of transitions from zero MPH to a specific speed, BOO switch input failure is presumed and Code 536 is set. Possible causes for this code are

1. Brakelight switch improperly installed.
2. Open brakelight/BOO switch circuit.
3. Damaged brakelight switch.
4. Poor brakelight ground connection.

Inspect brakelight switch for incorrect installation, poor alignment with pedal and damaged wiring. Repair if necessary, and repeat QUICK TEST. If all components are in good condition, go to step 91).

91) Check Brakelight For Ground Check brakelight connector and wires for corrosion and damage. If connector or wires are corroded or damaged, repair as necessary, and repeat QUICK TEST. If brakelight connector and wires are okay, go to step 92).

92) Check BOO Switch Circuits For Short To Power DO NOT depress brake pedal during this test. Turn ignition on. While watching brakelights, wiggle brakelight/BOO switch circuit wires and connectors. If brakelights flash, isolate and repair short to power. Repeat QUICK TEST. If brakelights do not flash, go to step 93).

93) Check Brakelight Circuit Continuity Turn ignition off. Depress and hold brake pedal. Observe brakelights. Tap brakelight switch to simulate road shock. Wiggle brakelight circuit wires and connectors. If brakelights blink or go off, isolate and repair open in brakelight circuit. Clear codes, and repeat QUICK TEST. If brakelights are on constantly and do not blink or go off, go to step 94).

94) Check Continuity Of BOO Switch Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect and repair any damaged terminals. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 2 at breakout box and brakelight circuit at brakelight switch connector. While observing DVOM, wiggle BOO switch circuit wires and connectors. If resistance is 5 ohms or more, isolate and repair open circuit in BOO switch circuit. Repeat QUICK TEST. If resistance is less than 5 ohms, fault cannot be duplicated at this time. See SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

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

1. Blower motor input circuit.
2. Daytime Running Lights (DRL) input circuit.
3. Headlight input circuit.
4. Rear window defrost input circuit.
5. ECA.

Electrical load inputs are used for idle speed control strategy so correct idle can be maintained regardless of electrical demands on engine. ECA uses 4 accessories to determine electrical load status: blower motor, headlights, rear window defroster, and daytime running lights (if equipped).

Electrical Load Input Circuit. Scheme 103

1) Isolate Faulty System If idle speed fault occurs when blower motor is on, go to step 10). If idle speed fault occurs when daytime running lights are on, go to step 20). If idle speed fault occurs when headlights are on, go to step 30). If idle speed fault occurs when rear window defroster is on, go to step 40).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 10). No test procedures have been omitted.

10) Check Blower Motor Switch (Low Speed) Turn ignition and all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Turn climate control motor switch to low-speed position "1" or "2". Measure voltage between test pin No. 14 at breakout box and chassis ground. If voltage is not 10-17 volts, go to step 13). If voltage is 10-17 volts, go to step 11).

11) Check Blower Motor Switch (High Speed) Turn ignition and all accessories off. Turn climate control motor switch to high-speed position "3" or "4". Turn ignition on. Measure voltage between test pin No. 14 at breakout box and chassis ground. If voltage is less than 1.5 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to step 12).

12) Check Blower Circuit For Short To Power Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 14 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check for damaged blower motor or relay. If resistance is 10,000 ohms or less, repair short circuit.

13) Check Blower Circuit Continuity Turn ignition off. Disconnect blower motor relay. Measure resistance between BLR terminal at power distributor box and test pin No. 14 at breakout box. If resistance is 5 ohms or more, repair open circuit. If resistance is less than 5 ohms, go to step 14).

14) Check Blower Circuit For Short To Power Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 14 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check for damaged blower motor or relay. If resistance is 10,000 ohms or less, repair short circuit.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 20). No test procedures have been omitted.

20) Check DRL Circuit Voltage (Headlights On) Turn ignition and all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Apply parking brake. Turn ignition on. Turn headlights on. Measure voltage between test pin No. 42 at breakout box and chassis ground. If voltage is not 10-17 volts, go to step 23). If voltage is 10-17 volts, go to step 21).

21) Check DRL Circuit Voltage (Headlights Off) Turn headlights off. Release parking brake. Turn ignition on. Measure voltage between test pin No. 42 at breakout box and chassis ground. If voltage is less than 1.5 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to step 22).

22) Check DRL Circuit For Short To Power Turn ignition off. Disconnect DRL relay. Measure resistance between test pin No. 42 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check daytime running lights module for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.

23) Check DRL Circuit Continuity Turn ignition off. Disconnect daytime running lights relay. Measure resistance between DRL relay connector and test pin No. 42 at breakout box. If resistance is 5 ohms or more, repair open circuit and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to step 24).

24) Check DRL Circuit For Short To Power Turn ignition off. Disconnect daytime running lights relay. Measure resistance between test pin No. 42 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check daytime running lights module for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 30). No test procedures have been omitted.

30) Check Headlight Circuit Voltage (Headlights Off) Turn ignition and all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 45 at breakout box and chassis ground. If voltage is 1.5 volts or more, go to step 34). If voltage is less than 1.5 volts, go to step 31).

31) Check Headlight Circuit Voltage (Headlights On) Turn all accessories off. Turn ignition on. Turn headlights on. Measure voltage between test pin No. 45 at breakout box and chassis ground. If voltage is 10-17 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is not 10-17 volts, go to step 32).

32) Check HDL Circuit Continuity Turn ignition off. Disconnect headlight relay. Measure resistance between HDL terminal at power distribution box and test pin No. 45 at breakout box. If resistance is 5 ohms or more, repair open circuit and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to step 33).

33) Check HDL Circuit For Short To Ground Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 45 and test pins No. 40, 46 and 60 at breakout box. If each resistance is more than 10,000 ohms, check headlight switch for malfunction. If any circuit resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.

34) Check HDL Circuit For Short To Power Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 45 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check headlight switch for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 34) to step 40). No test procedures have been omitted.

40) Check DEF Circuit Voltage (Defrost Off) Turn ignition off. Turn all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 15 at breakout box and chassis ground. If voltage is 10-17 volts, go to step 41). If voltage is not 10-17 volts, go to step 43).

41) Check DEF Circuit Voltage (Defrost On) Turn ignition on. Turn rear window defroster on. Measure voltage between test pin No. 15 at breakout box and chassis ground. If voltage is less than 3 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 3 volts or more, go to step 42).

42) Check DEF Circuit For Short To Power Turn ignition off. Disconnect rear window defroster relay. Measure resistance between test pin No. 15 and test pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check DEF switch or relay for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.

43) Check DEF Circuit Continuity Turn ignition off. Disconnect rear window defroster switch. Measure resistance between DEF terminal at power distribution box and test pin No. 15 at breakout box. If resistance is less than 5 ohms, go to step 44). If resistance is 5 ohms or more, repair open circuit and confirm idle speed fault has been corrected.

44) Check DEF Circuit For Short To Ground Turn ignition off. Disconnect rear window defroster relay. Measure resistance between test pin No. 15 and test pins No. 40, 46 and 60 at breakout box. If each circuit resistance is more than 10,000 ohms, check DEF switch and relay circuit for malfunction. If any circuit resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Some vehicles may not have power steering, but ECA may be equipped with PSPS software strategy. Disregard KOEO Code 52/519 if vehicle is not equipped with power steering. This test is only intended to diagnose

1. Power Steering Pressure Switch (PSPS).
2. PSPS and SIG RTN wiring harness circuits.
3. ECA.

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

1. Idle speed/throttle stop adjustment.
2. Binding throttle shaft/linkage.
3. Cruise control linkage.
4. Power steering hydraulic system.

Power Steering Pressure Switch (PSPS) Circuit. Scheme 104

CIRCUIT TEST FF TEST PIN WIRE COLOR ID

1) Code 52/519: Attempt To Eliminate Code Code 52/519 indicates PSPS circuit is open. Turn ignition off. Disconnect PSPS switch. Install jumper wire between PSPS terminal and SIG RTN terminal at wiring harness connector. Repeat KOEO SELF-TEST. If Code 52/519 is not displayed, replace PSPS and repeat QUICK TEST. If Code 52/519 is displayed, remove jumper wire and go to step 2).

2) Check Continuity Of PSPS Circuits Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and SIG RTN terminal at PSPS wiring harness connector. Also measure resistance between test pin No. 24 at breakout box and PSPS terminal at switch wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST. If readings are 5 ohms or more, repair open circuit and repeat QUICK TEST.

3) Check PSPS Operation Turn ignition off. Connect tachometer, and start engine. Allow engine to idle in Park or Neutral. Disconnect PSPS switch connector. If RPM increases, replace PSPS switch and recheck system. If RPM does not increase, go to step 4).

4) Check PSPS Circuits For Shorts Turn ignition off. Disconnect PSPS switch. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If resistance is 10,000 ohms or less, repair short in harness and recheck symptom. If reading is more than 10,000 ohms, replace ECA and recheck symptom.

5) KOER SELF-TEST Code 52/521 Disregard this code if vehicle does not have power steering. Code 52/521 indicates PSPS did not change states due to open or closed switch. If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and front wheels were centered in a no-load condition, go to step 6). If steering wheel was not turned, repeat QUICK TEST.

6) Check ECA Open Circuit Identifying Capabilities Turn ignition off. Disconnect PSPS. Perform KOEO SELF-TEST. If Code 52/519 is present, go to step 8). If Code 52/519 is not present, go to step 7).

7) Check PSPS Circuits For Shorts Turn ignition off. Disconnect PSPS switch. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. If reading is more than 10,000 ohms, replace ECA and repeat QUICK TEST.

8) Check PSPS Position Comparison Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. With PSPS connected, set DVOM on 200-ohm scale. Turn ignition on. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. Start engine. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If reading shows less than 10 ohms difference between key on engine off and key on engine running, go to step 9). If reading is not as described, replace PSPS switch and repeat QUICK TEST.

9) Check PSPS With Engine Running (Load & No Load) Connect PSPS, and set DVOM on 200-ohm scale. Start engine, and allow it to idle. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. Turn steering wheel 1/2 turn and return to center position. If resistance changes from less than 10 ohms to infinity and then returns to 10 ohms or less (when steering wheel is centered), PSPS system is okay. Testing is complete. If reading does not change as indicated, replace PSPS switch.

10) Code 519: Attempt To Eliminate Code 519 Disregard this code if vehicle does not have power steering. Code 519 indicates PSPS circuit is closed. Turn ignition off. Disconnect PSPS switch connector. Repeat KOEO SELF-TEST. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If Code 519 is not present, replace PSPS switch. If Code 519 is present, go to step 11).

11) Check PSPS Circuit For Short Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. If reading is more than 10,000 ohms, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 15). No test procedures have been omitted.

15) Check PSPS Operation Connect tachometer, and start engine. Allow engine to idle in Park or Neutral. Disconnect PSPS switch connector. If RPM increases, replace PSPS switch and recheck system. If RPM does not increase, go to step 16).

16) Check Continuity Of PSPS Circuits Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and SIG RTN terminal at PSPS wiring harness connector. Also measure resistance between test pin No. 24 at breakout box and PSPS terminal at PSPS wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST. If any reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 16) to step 20). No test procedures have been omitted.

20) KOER SELF-TEST Code 521 Disregard this code if vehicle does not have power steering. Code 521 indicates PSPS did not change states due to open or closed switch. If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and front wheels were centered in a no-load condition, go to step 21). If steering wheel was not turned, repeat QUICK TEST.

21) Check ECA Closed Circuit Identifying Capabilities Turn ignition off. Disconnect PSPS switch. Connect jumper wire between PSPS terminal and SIG RTN terminal at PSPS switch wiring harness connector. Perform KOEO SELF-TEST. If Code 519 is present, remove jumper wire and go to step 23). If Code 519 is not present, go to step 22).

22) Check Continuity Of PSPS Circuits Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 24 at breakout box and PSPS terminal at PSPS wiring harness connector. Also measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at PSPS wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST. If either reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

23) Check PSPS Position Comparison Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. With PSPS connected, set DVOM on 200-ohm scale. Turn ignition on. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. Start engine. If reading shows less than 10 ohms difference between key on engine off and key on engine running, go to step 24). If reading is not as described, replace PSPS switch and repeat QUICK TEST.

24) Check PSPS With Engine Running (Load & No Load) Start engine, and allow it to idle. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. Turn steering wheel 1/2 turn and return to center position. If resistance changes from less than 10 ohms to infinity and then returns to 30 ohms or less (when steering wheel is centered), PSPS system is okay. Testing is complete. If reading does not change as indicated, replace PSPS switch.

CIRCUIT TEST H - FUEL CONTROL

Note. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Fuel-contaminated engine oil may affect Codes 41/172, 91/136, 42/173 and 92/137. If fuel-contaminated engine oil is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter. Only use this test to diagnose

1. HEGO sensor.
2. HEGO signal, ground circuit and sensor connection.
3. Vacuum systems.
4. Fuel injector and/or fuel injector circuitry.
5. ECA.
6. Electrical circuits (HEGO GND, HEGO, INJ 1-8, VPWR and SIG RTN).

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

1. Ignition system.
2. Faulty evaporative emission system.
3. EGR system.
4. Air intake system.
5. Engine oil contamination.
6. Fuel system.
7. Intake or exhaust system leaks.
8. Engine cooling system.

INDIVIDUAL INJECTOR RESISTANCE (1)

INJECTOR BANK RESISTANCE

Test Schematic. Scheme 105

CIRCUIT TEST H ACRONYMS

1) Check For Contaminated Engine Oil Turn ignition off. Remove PCV valve from valve cover. Inspect PCV system for damage. Inspect valve for blockage and movement of valve plunger. Repair as necessary. Perform KOER SELF-TEST. If vehicle is a no-start, KOER Code 41/172, 42/173, 91/136 or 92/137 or Continuous Memory Code 41/144, 91/139, or 172 is present, install PCV valve and go to step 2). If no codes are set, change engine oil and filter. Install PCV valve, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

2) Check Fuel Pressure Turn ignition off. Install fuel pressure gauge. Ensure manifold vacuum supply is connected to fuel pressure regulator (if equipped). Run engine at idle and check fuel pressure. If vehicle will not start, cycle ignition on and off several times. Check fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specification, go to step 3). If pressure is not within specification, go to FUEL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

3) Check System Ability To Hold Fuel Pressure Turn ignition on. If fuel pressure remains at specification for 60 seconds, go to step 4) (no-starts), step 5) (non-SEFI) or step 6) (SEFI). If fuel pressure is not as described, repair fuel delivery system as necessary.

4) Fuel Delivery Test Release fuel system pressure. Install fuel pressure gauge, and pressurize fuel system as in step 1). Disconnect inertia switch. Crank engine 5 seconds. If fuel pressure drop is greater than 5 psi after 5 seconds of cranking, EEC-IV system is not causing no-start condition. Check additional no-start tests in TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If fuel pressure drop is less than 5 psi, remove fuel pressure gauge. Connect inertia switch. Go to step 7) for non-SEFI or step 8) for SEFI.

5) Cylinder Balance Test (Non-SEFI) Connect a tachometer to engine. Start engine, and run it at idle. Disconnect and reconnect injectors individually, noting RPM drop as each injector is disconnected. ISC motor will attempt to re-establish RPM. If each injector does not produce a momentary drop in RPM, go to step 7). If each injector produces a momentary drop in RPM, go to step 13) for Codes 41/172, 91/136 or 176. For Codes 42/173, 92/137 or 177, go to step 24). Go to step 14) for all other codes.

6) Cylinder Balance Test (SEFI) Perform KOER SELF-TEST. After last code is displayed, wait 5-10 seconds. Enter CYLINDER BALANCE TEST by lightly goosing throttle (not WOT). Test time is about 2-3 minutes. To interpret codes retrieved from test, refer to CYLINDER BALANCE TEST SERVICE CODES . If cylinder balance fault code is present, go to step 8). If a cylinder balance fault code is not present, fuel delivery is okay; fault is in area common to all cylinders. Code 77/538 indicates throttle was touched when test was ran and test is not completed. Code 538 could also be output if Continuous Memory Code 214 (CID) is present. If Continuous Memory Code 214 is present, see appropriate chart under SERVICE CODE REFERENCE CHARTS for instruction. For symptoms or Code 41/172, 91/136 or 176, go to step 13). For Code 42/173, 92/137 or 177, go to step 24). For all other codes, go to step 14).

CYLINDER BALANCE TEST SERVICE CODES

7) Check Injector & Harness Resistance (Non-SEFI) Turn ignition off. Wait 10 seconds. Disconnect ECA 60-pin connector. Inspect pins for damage and repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance of injector banks between test pins No. 37 and 58 at breakout box. Measure resistance of injector banks between test pins No. 37 and 59 at breakout box. Record resistances. Refer to INJECTOR BANK RESISTANCE in this circuit test. If each resistance is within specifications, go to step 12). If resistance is not as specified, repair open circuit on VPWR circuit (for no-start) or go to step 9) (for all other conditions).

8) Check Injector & Harness Resistance (SEFI) Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure and record resistance between suspected injector circuit test pin and test pin No. 37. For no starts, measure and record resistance between any injector circuit test pin and test pin No. 37. Refer to INJECTOR BANK RESISTANCE table in this circuit test. If each resistance is within specification, go to step 12). If resistance is not as specified, repair open circuit on VPWR circuit (for no-start) or go to step 9 (for all other conditions).

9) Check Continuity Of Fuel Injector Harness Turn ignition off. Disconnect injector wiring harness connector at injectors. Set DVOM to 200-ohm scale. Measure resistance between test pins No. 37 and 57 at breakout box and each injector VPWR terminal at wiring harness connector. Measure resistance between injector test pin(s) at breakout box and same injector circuit terminal at each injector wiring harness connector. If each resistance is less than 5 ohms, go to step 10). If each resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

10) Check Injector Harness Circuit For Short To Power Or Ground Turn ignition off, and wait for 10 seconds. With breakout box installed and ECA disconnected, disconnect fuel injector wiring harness. Set DVOM to 200-k/ohm scale. Measure resistance between injector test pin(s) and test pins No. 37, 40, 46, 57 and 60. Measure resistance between injector test pin(s) at breakout box and chassis ground. If each resistance is 10,000 ohms or more, replace injector per cylinder balance test service code and repeat QUICK TEST (SEFI) or go to next step (non-SEFI). If each resistance is less than 10,000 ohms, repair short. Remove breakout box, reconnect all components and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

11) Isolate Faulty Injector Circuit Turn ignition off. Install breakout box, and disconnect ECA. Disconnect all injectors on suspect bank. With DVOM set on 200-ohm scale, connect one injector and measure resistance between test pins No. 37 and 58 (injector bank No. 1) or 59 (injector bank No. 2). Disconnect injector, and repeat process for all other injectors. See INDIVIDUAL INJECTOR RESISTANCE . If all injectors are within specification, go to step 12). If injectors are not as specified, replace injector. Remove breakout box, and reconnect components. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

12) Check Injector Drive Signal With ignition off and breakout box installed, connect ECA to breakout box. Use a non-powered 12-volt test light, and connect as follows

1. Non-SEFI Connect test light between test pins No. 37 and 58 at breakout box. Connect light between test pins No. 37 and 59 at breakout box.
2. SEFI Connect test light between test pin No. 37 and suspect injector test pin at breakout box.

Crank or start engine. If test light glows dimly, system is operating correctly. Clean injectors, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST and CYLINDER BALANCE TEST. If test light does not glow dimly (no light/bright light), replace ECA. Reconnect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

13) Check Thermactor Operation If vehicle is equipped with pulse-air or does not have thermactor system, go to next step 14). A HEGO which is always lean could be caused by thermactor air being diverted upstream from HEGO sensor. With dual HEGO, Code 41/172 applies to right or rear HEGO and Code 91/136 or 176 applies to left or front HEGO. Turn ignition off. Disconnect thermactor air hose(s) from thermactor pump. Run KOER SELF-TEST. If Code 41/172, 91/136 or 176 is present, reconnect thermactor air hoses and go to step 90). If no codes are present, repair thermactor system as necessary.

14) Check HEGO Integrity A HEGO sensor which is always lean, slow to switch or does not switch could be caused by

1. Moisture inside HEGO sensor or connector causing a short to ground.
2. HEGO sensor coated with contaminants.
3. HEGO circuit open.
4. HEGO circuit shorted to ground.

Turn ignition off. Inspect HEGO wiring harness for damage. Inspect HEGO sensor and connector for signs of fluid entry. Repair or replace as necessary. Start engine, and run it at 2000 RPM for 2 minutes. Turn ignition off. Run KOER SELF-TEST. If fault codes are present, go to step 15) (MAP sensor-equipped models) or step 16) (MAF sensor-equipped models). If no code is present, go to step 21).

15) Check HEGO Sensor (Engines With MAP Sensors) Vacuum or air leaks in non-EEC-IV areas could cause Code 41, 91, 136, 172 or 176. Check following possibilities before continuing

1. Leaking vacuum actuated motor.
2. Leaking intake gasket.
3. EGR system.
4. PCV system.
5. Lead-contaminated HEGO sensor.

Turn ignition off. Ensure MAP sensor output voltage is correct. See CIRCUIT TEST DF, step 3). Disconnect appropriate HEGO sensor from wiring harness. Connect DVOM to HEGO SIGNAL lead at sensor from wiring harness. On 3-wire HEGO, connect DVOM to HEGO SIGNAL lead at sensor connector and battery negative terminal. On 4-wire HEGO, connect DVOM to HEGO SIGNAL and HEGO GND leads at sensor connector. On all models, disconnect and plug vacuum line at MAP sensor. Start engine, and apply 10-14 in. Hg to MAP sensor. Run engine at 2000 RPM for 2 minutes. If reading is 0.5 volt or more, go to step 17). If reading is less than 0.5 volt, replace HEGO sensor and repeat QUICK TEST.

16) Check HEGO Sensor (Engines With MAF Sensor) Purpose of this test is to verify HEGO sensor can generate a voltage signal of greater than 0.5 volt during KOER SELF-TEST. With ignition off and DVOM set on 20-volt scale, disconnect appropriate HEGO sensor from harness. On 4-wire HEGO, connect DVOM between HEGO SIGNAL and HEGO GND at HEGO sensor connector. On 3-wire HEGO, connect DVOM to HEGO SIGNAL at sensor and battery negative terminal. On all models, run engine at 2000 RPM for 2 minutes. Repeat KOER SELF-TEST and monitor HEGO sensor voltage. If voltage is 0.5 volt or more at end of self-test, go to step 17). If voltage is less than 0.5 volt, replace HEGO sensor and repeat QUICK TEST.

17) Check Continuity Of HEGO Circuits Turn ignition off. Install breakout box, leaving ECA disconnected. Disconnect suspect HEGO sensor from wiring harness. Inspect both ends of connector for damage, moisture and corrosion. Repair as necessary. Set DVOM on 200-ohm scale. Measure resistance between HEGO SIGNAL (test pin No. 29) at breakout box and HEGO SIGNAL at wiring harness connector. On 3-wire HEGO, measure resistance between HEGO GROUND test pin at breakout box and battery negative terminal. On 4-wire HEGO, measure resistance between HEGO GROUND test pin at breakout box and HEGO GND at wiring harness connector. Where applicable, measure resistance between HEGO GND and SIG RTN at breakout box. On all models, go to step 18) if each resistance is less than 5 ohms. If any resistance is 5 ohms or more, repair open circuit. Remove breakout box, and reconnect all components. Drive vehicle for 5 minutes at 55 MPH. Repeat QUICK Test.

18) Check HEGO Circuit For Short To Ground Turn ignition off. Leave breakout box installed and ECA disconnected. Disconnect HEGO sensor. Measure resistance between HEGO SIGNAL and test pins No. 40, 46 and 49 at breakout box. If any reading is less than 10,000 ohms, repair short to ground. Reconnect all components, and repeat QUICK TEST. If reading is 10,000 ohms or more, go to step 19).

19) Check HEGO Sensor For Short To Ground Disconnect HEGO sensor. On 4-wire HEGO, measure resistance between PWR GND, HEGO GND, SIG RTN and HEGO SIG at HEGO sensor connector. On all HEGO sensors, measure resistance between PWR GND and HEGO SIGNAL at HEGO sensor connector. If resistance is less than 10,000 ohms, replace HEGO sensor. Connect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. If resistance is 10,000 ohms or more, perform following procedure as applicable.

1. For Codes 144/41, 139/91, 171, 174, 175 and 178, go to step Step 90) .
2. For all other codes, go to step 20) if engine is equipped with MAP sensor. If engine is equipped with MAF sensor, replace ECA. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST.

20) Attempt To Eliminate Code 41/172, 91/136 Or 176 (Engines With MAP Sensor) Turn ignition off. Connect ECA to breakout box. Connect HEGO sensor. Disconnect and plug MAP sensor vacuum hose. Apply 10-14 in. Hg to MAP sensor. Start and run engine at 2000 RPM for 2 minutes. Allow engine to return to idle. Perform KOER SELF-TEST. If diagnosing continuous memory codes, drive vehicle 5 miles at 55 MPH. If Code 41/172, 91/136 or 176 is still present, remove breakout box. Connect all components. If engine runs rough, go to step 2) of CIRCUIT TEST S. If engine does not run rough, replace ECA, drive vehicle 5 miles at 55 MPH and repeat QUICK TEST. If code is not present, remove breakout box and connect all components. HEGO input circuit and fuel delivery are okay; fault is in area common to all systems. See TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

21) Check Resistance Of HEGO Heating Element Turn ignition off. Disconnect suspect HEGO sensor. Inspect both ends of connector for damage, moisture and corrosion. Repair if necessary. Set DVOM on 200-ohm scale. Measure resistance between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connector. Hot to warm engine resistance should be 5-30 ohms. Cold engine resistance is 2-5 ohms. If resistance is within specification, go to step 22). If resistance is not as specified, replace HEGO sensor and repeat QUICK TEST.

22) Check For Power At HEGO Harness Connector Disconnect HEGO sensor. Turn ignition on. Measure voltage between IGNITION RUN and PWR GND circuits at HEGO wiring harness connector. If voltage is 10.5 volts or more, HEGO system and fuel delivery are okay. HEGO sensor may have cooled before KOER SELF-TEST. If driveability symptom continues, fault is in area common to all cylinders. See TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If voltage is less than 10.5 volts, go to step 23).

23) Check Continuity Of Power Ground Circuit Turn ignition off. Measure resistance between PWR GND circuit at HEGO wiring harness connector and negative battery terminal. If resistance is less than 5 ohms, repair open in IGNITION RUN circuit and repeat QUICK TEST. If resistance is 5 ohms or more, repair open in PWR GND circuit and repeat QUICK TEST.

24) Check HEGO SIGNAL For Short To Power On dual HEGO systems, Code 42/173 applies to right or rear HEGO. Codes 92/137 and 177 applies to left or front HEGO. Turn ignition off. Disconnect appropriate HEGO sensor. Turn ignition on. Measure voltage between HEGO SIG and PWR GND at HEGO wiring harness connector. If reading is less than 0.5 volt, go to step 26). If reading is 0.5 volt or more, go to step 25).

25) Check For Short To Power Turn ignition off. Disconnect HEGO sensor. Inspect both ends of connector for damage, moisture and corrosion. Repair if necessary. Drive vehicle 5 miles at 55 MPH and repeat QUICK TEST. If connector is okay, go to step 26).

26) Check HEGO Sensor For Short To IGNITION RUN Circuit Turn ignition off, and wait 10 seconds. Disconnect HEGO. Set DVOM to 200-k/ohm scale. Measure resistance between IGNITION RUN circuit and HEGO SIG circuit at HEGO sensor connector. If resistance is 10,000 ohms or more, go to step 27) for Codes 42/173, 92/137 and 177; for codes 171, 174, 175 and 178, go to step 28) (MAP sensor) or 30) (MAF sensor). If resistance is less than 10,000 ohms, replace HEGO sensor. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST.

27) Attempt To Generate Code 41/172, 91/136 Or 176 Turn ignition off. Disconnect appropriate HEGO sensor. Using jumper wire, connect HEGO SIG circuit at HEGO wiring harness connector to negative battery terminal. Repeat KOER SELF-TEST. If Code 41/172, 91/136 or 176 is present, remove jumper wire and go to step 28) for engines with MAP sensor or step 30) for engines with MAF sensor. If Codes 41/172, 91/136 and 176 are not present, remove jumper wire. Disconnect ECA connector, and inspect it for damage. If connector is okay, replace ECA. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

Because MAP sensor greatly influences fuel control, MAP sensor may malfunction without setting Code 22/126. Next 2 steps test MAP vacuum circuit.

28) Check MAP Sensor For Vacuum Leaks Turn ignition off. Disconnect vacuum hose from MAP sensor. Connect vacuum pump to sensor. Apply 18 in. Hg to MAP sensor. If sensor does not hold vacuum, replace MAP sensor. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. If sensor holds vacuum, release vacuum and go to step 29).

29) Check For Loss Of Vacuum To MAP Sensor Using vacuum "T", connect vacuum gauge in MAP sensor vacuum hose. Start engine. Note vacuum reading at idle stabilizes. Turn ignition off. Remove "T" and vacuum gauge. Reconnect hose to MAP sensor. Connect vacuum gauge at a different manifold vacuum location. Start engine, and note vacuum reading. If readings do not differ by more than 1 in. Hg, go to next step. If readings differ by more than 1 in. Hg, inspect vacuum hoses for leaks, kinks and blockage. Repair as necessary. Connect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

30) HEGO Sensor Check Turn ignition off. Disconnect HEGO sensor. For 4-wire HEGO sensor, connect DVOM to HEGO and HEGO GND or SIG RTN at HEGO sensor connector. For 3-wire HEGO sensor, connect DVOM to HEGO SIGNAL at HEGO sensor connector and negative battery terminal. On all models, remove PCV valve from hose. Start engine, and run it at about 2000 RPM. DVOM should indicate less than 0.4 volt within 30 seconds. If voltage is not as specified, replace HEGO sensor. Reconnect vacuum hoses, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. If voltage is as specified, go to step 90).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 30) to step 90). No test procedures have been omitted.

90) Check Continuous Monitor Mode Start engine, and warm it to normal operating temperature. Raise engine speed to 2000 RPM for 2 minutes and then return to idle. Enter KOER wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. While observing DVOM or scan tester, shake or bend small sections of wiring harness from HEGO sensor to ECA. Wiggle, shake or bend small sections of wiring harness from HEGO GND to ECA. If no fault is indicated, remain in CONTINUOUS MONITOR MODE and go to step 91). If fault is indicated, isolate and repair fault as necessary. Clear codes. Repeat QUICK TEST.

91) Continuous Monitor Test Drive Check While still in KOER wiggle test, drive vehicle for 5 miles at 55 MPH over smooth roads. Drive an additional 5 miles at 55 MPH over rough roads. If possible, drive vehicle through a pool of water to wet HEGO sensor and connector. If fault is indicated, isolate fault and repair as necessary. Clear codes, and remove breakout box. Repeat QUICK TEST. If no codes are indicated, exit KOER wiggle test and go to next step.

92) Check HEGO Switching Turn ignition off. Inspect wire harness for proper routing. Check for burnt, chaffed or open wires. Repair if necessary. Disconnect ECA 60-pin connector. Inspect it for damaged or pushed-out pins and repair as necessary. Install breakout box. Connect ECA to breakout box. Connect analog voltmeter to suspect HEGO sensor test pin and HEGO GND at breakout box. Test drive vehicle for 5 miles at 55 MPH while observing voltmeter. HEGO should switch fluctuate between .3 and .9 volt in 3 second cycles. If HEGO does not switch as described, replace HEGO sensor. Connect all components, and repeat QUICK TEST. If HEGO switches as described, fault cannot be identified at this time. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

CIRCUIT TEST HA - ADAPTIVE FUEL

Note. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.

Perform this test when directed by QUICK TEST. ECA uses adaptive fuel logic to compensate for normal variances in fuel system components. If fuel system appears to be too rich or too lean, adaptive fuel will make appropriate shift in fuel delivery calculations to compensate.

If possible, measure several known good MAP/BP sensors. Average voltage reading will be typical for location and day of testing.

MAP SENSOR VOLTAGE OUTPUT

CIRCUIT TEST HA ACRONYMS

1) Continuous Memory Codes 181, 183, 189 & 192 This test identifies areas which could cause HEGO sensor to detect excessive oxygen, resulting in adaptive fuel enriching system to compensate. Excessive oxygen will be detected with lean conditions and certain rich conditions. For models with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem common to all cylinders. If a code is present from only one HEGO, this may help isolate a problem or be an early indication of a common problem.

1. Code 183 Indicates single right or rear HEGO detected a problem and adaptive fuel rich limit has been reached at idle.
2. Code 192 Indicates left or front HEGO detected a problem and adaptive fuel rich limit has been reached at idle.
3. Code 181 Indicates single right or rear HEGO detected a problem and adaptive fuel rich limit has been reached.
4. Code 189 Indicates left or front HEGO detected a problem and adaptive fuel rich limit has been reached.

Ensure a pass Code (111) is retrieved during both KOEO SELF-TEST and KOER SELF-TEST. Whenever a repair is made, clear KAM. If driveability symptoms are not present, be aware of other temporary conditions which may have set this code, such as fuel contamination or vehicle is out of fuel. For SEFI models, go to step 2). For non-SEFI models, go to step 3).

2) Run Cylinder Balance Test Run KOER SELF-TEST. After last repeated code, wait 5-10 seconds then goose throttle lightly (not WOT). Cylinder balance test will be activated. If Code 90 is present, go to next step. If Code 90 is not present, go to step 35).

3) Check For Vacuum/Air Induction Leaks Check vacuum hoses, air induction system and EGR tube for leaks and damage. Repair if necessary. Clear KAM, and repeat QUICK TEST. If leak or damage is not found, go to step 4).

4) Check For Low Fuel Pressure Turn ignition off. Release fuel system pressure. Install fuel pressure gauge. Cycle ignition from OFF to RUN position twice. Observe KOEO fuel pressure. Start engine. Observe and record KOER fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specification, go to step 5). If fuel pressure is not within specification, repair fuel system. Clear KAM, and repeat QUICK TEST.

5) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from OFF to ON position twice to pressurize fuel system (DO NOT start engine). If fuel pressure remains at specification for 60 seconds, go to step 6) (MAP/BP equipped vehicles) or step 7) (all other vehicles). If fuel pressure does not remain at specification for 60 seconds, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST.

6) Check MAP/BP Frequency Turn ignition off. Connect MAP/BP tester to MAP/BP sensor. (Scheme 93)in CIRCUIT TEST DF. Turn ignition on. If MAP/BP voltage is within specification, go to step 7). See MAP SENSOR VOLTAGE OUTPUT. If voltage is not within specification, check wiring to MAP/BP sensor for corrosion and other damage. Repair as necessary. Clear KAM, and repeat QUICK TEST. If wiring is okay, replace MAP/BP sensor. Clear KAM, and repeat QUICK TEST.

7) Check For Proper Battery Voltage To Fuel Injectors Turn ignition on. Measure and record voltage across battery terminals. Disconnect any fuel injector harness connector. Measure and record voltage between VPWR circuit at fuel injector wiring harness connector and battery negative terminal. If both voltage readings are within one volt of each other, go to step 8). If voltage readings differ by more than one volt, fuel injectors are not getting correct voltage. Repair as necessary. Clear KAM, and repeat QUICK TEST.

8) Verify CANP Solenoid Is Not Stuck Closed Enter OUTPUT STATE CHECK. See ADDITIONAL SYSTEM FUNCTIONS. Disconnect hose to manifold vacuum at CANP solenoid. Check for blockage. Repair or replace hose as necessary. With outputs off, apply 16 in. Hg vacuum to manifold vacuum side of CANP. Apply throttle to cycle outputs on. If vacuum releases, reconnect vacuum hose to CANP and go to step 9) (thermactor-equipped vehicles) or step 25) (all other vehicles). If vacuum does not release, repeat this step to verify results. If vacuum now releases, go to step 9) (thermactor-equipped vehicles) or step 25) (all other vehicles). If vacuum will not release, replace CANP solenoid. Clear KAM, and repeat QUICK TEST.

9) Check Thermactor System For Upstream Air Leak Check thermactor air control and vacuum control valves. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If air control valve is operating properly, go to step 25). If air control valve is not operating properly, repair or replace valve as necessary. Clear KAM, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 9) to step 15). No test procedures have been omitted.

15) Continuous Memory Codes 179, 182, 188 & 191 This test identifies areas which could cause engine to run rich, resulting in adaptive fuel reducing system to compensate. For vehicles with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem common to all cylinders. If a code is present from only one HEGO, this may help isolate a problem or it may be an early indication of a common problem.

1. Code 179 Indicates single right or rear HEGO detected a problem and adaptive fuel lean limit has been reached.
2. Code 182 Indicates single right or rear HEGO detected a problem and adaptive fuel lean limit has been reached at idle.
3. Code 188 Indicates left or front HEGO detected a problem and adaptive fuel lean limit has been reached.
4. Code 191 Indicates left or front HEGO detected a problem and adaptive fuel lean limit has been reached at idle.

Ensure a pass Code (111) is received during both KOEO SELF-TEST and KOER SELF-TEST. Whenever a repair is made, clear KAM. For SEFI vehicles, go to step 16). For non-SEFI vehicles, go to step 17).

16) Run Cylinder Balance Test Run KOER SELF-TEST. After last repeated code, wait 5-10 seconds and then goose throttle lightly (not WOT). Cylinder balance test will be activated. If Code 90 is present, go to next step. If Code 90 is not present, go to step 35).

17) Check For Low Fuel Pressure Turn ignition off. Release fuel system pressure. Install fuel pressure gauge. Cycle ignition from OFF to RUN position twice. Observe KOEO fuel pressure. Start engine. Observe and record KOER fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specification, go to step 18). If fuel pressure is not within specification, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST.

18) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from OFF to ON position twice to pressurize fuel system (do not start engine). If fuel pressure remains at specification for 60 seconds, go to step 19) (MAP/BP-equipped vehicles) or step 20) (all other vehicles). If fuel pressure does not remain at specification for 60 seconds, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST.

19) Check MAP/BP Frequency Turn ignition off. Connect MAP/BP tester to MAP/BP sensor. Turn ignition on. Refer to MAP SENSOR VOLTAGE OUTPUT . If voltage is not within specification, check wiring to MAP/BP sensor for corrosion or other damage. Repair if necessary. Clear KAM, and repeat QUICK TEST. If wiring is okay, replace MAP/BP sensor. Clear KAM, and repeat QUICK TEST. If MAP/BP voltage is within specification, go to step 20).

20) Check Throttle Body & Air Induction System Check throttle body and air induction system for contamination and obstruction. Repair if necessary. Clear KAM, and repeat QUICK TEST. If throttle body and air induction system are okay, go to step 21).

21) Check PCV Valve Turn ignition off. Remove and shake PCV valve. If PCV valve rattles freely when shaken, go to step 26). Replace PCV valve if it does not rattle. Clear KAM, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 26). No test procedures have been omitted.

26) Check HEGO Heater Circuit Turn ignition off. Disconnect HEGO sensor(s). Measure resistance between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connectors. Resistance should be 2 ohms (cold) or 35 ohms (hot). Set DVOM to 20-volt scale. Turn ignition on. Measure voltage between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connectors. Voltage should be 10.5 volts. If HEGO circuit checks are within specification, go to step 27). If HEGO circuit check are not within specification, isolate problem and repair as necessary. Clear KAM, and repeat QUICK TEST.

27) Inspect HEGO Sensor For Contamination Remove HEGO sensor(s) from exhaust manifold. Visually inspect for contamination and other damage. If HEGO sensors appear okay, go to step 28) (models with EGR) or step 30) (models without EGR). If HEGO sensors are contaminated or damaged, replace HEGO sensor. Clear KAM, and repeat QUICK TEST.

28) Check EGR Vacuum Supply At Idle Disconnect vacuum line at EGR valve. Connect vacuum gauge to EGR vacuum line. Start engine, and let it idle. If vacuum reading is less than 2.5 in. Hg, go to step 29). If vacuum reading is 2.5 in. Hg or more, check EVR solenoid filter for obstructions. Repair as necessary. If EVR filter is okay, replace EVR solenoid. Connect all components, clear KAM, and repeat QUICK TEST.

29) Verify EGR Valve Is Fully Seated Inspect EGR valve to ensure proper seating. If EGR valve is fully seated, reconnect vacuum line to EGR valve and go to step 30). If EGR valve is not fully seated, service or replace EGR valve as necessary. Clear KAM, and repeat QUICK TEST.

30) Check Cooling System Ensure cooling system is in good condition and all components are operating properly. If cooling system is okay, go to step 35). If cooling system requires service, repair or replace as necessary. Clear KAM, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 30) to step 35). No test procedures have been omitted.

35) Check Ignition System Ensure ignition system is operating properly. Scope check engine to verify no abnormal primary or secondary ignition firing lines exist. If ignition system is operating properly, go to step 36). If system is not operating properly, make necessary repairs. See IGNITION SYSTEMS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Clear KAM, and repeat QUICK TEST.

36) Injector Flow Check Check fuel injector flow using Fuel Injector Tester (Rotunda 113-00001). If injector flow is okay, go to step 37). If injectors are restricted, clean or replace injectors as necessary. Clear KAM, and repeat QUICK TEST.

37) Check Cylinder Compression Check cylinder compression. See MECHANICAL INSPECTION in BASIC TESTING article in the ENGINE PERFORMANCE Section. If cylinder compression is not within specifications, repair or replace engine as necessary. Clear KAM, and repeat QUICK TEST. If cylinder compression is within specification, go to step 40).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 37) to step 40). No test procedures have been omitted.

40) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a driveability fault or symptom. To prepare for road test

1. Install fuel pressure gauge.
2. Install MAP/BP tester.
3. Disconnect ECA 60-pin connector, install breakout box and reconnect ECA to breakout box.
4. Connect "T" vacuum gauge into manifold vacuum line.
5. Have DVOM, writing materials, appropriate schematics and pin voltage charts available.

With ignition on and negative lead of DVOM connected to battery negative terminal, ensure following signals are correct

1. POWERS: KAPWR (pin No. 1) is more than 10.5 volts, VPWR (pins No. 37 and 57) is more than 10.5 volts and VREF (pin No. 26) is 4-6 volts.
2. GROUNDS: PWR GND (pins No. 40 and 60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0-.5 volt.
3. OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. 20) and MAF RTN (pin No. 9 or 15) are 0-.5 volt.

Drive vehicle and attempt to induce symptom. Information provided by vehicle operator may help when trying to recreate symptom. When symptom occurs, assistant should observe and record changes in voltage signals. Information about symptom, operating condition value of voltage signal and any other information available should be recorded for analysis. If unable to duplicate symptom during road test, verify EEC-IV values are within acceptable range. After road test is completed, analyze results to locate and repair fault causing symptom. If problem cannot be identified, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes of symptom.

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

1. Fuel pump relay.
2. Inertia switch.
3. Wiring harness circuits (BATT +, VPWR, FUEL PUMP, GND and POWER-TO-PUMP).
4. ECA.

Fuel Pump Monitor Circuit Diagram (Typical). Scheme 106

CIRCUIT TEST J TEST PIN WIRE COLOR ID

Fuel Pump Monitor Ckt. Diagram (Bronco & Pickup). Scheme 107

Fuel Pump Monitor Ckt. Diagram (Van). Scheme 108

1) No Fuel System Pressure: Check Fuel Pump Operation Turn ignition switch from OFF to RUN position several times (DO NOT turn to START position). If fuel pump runs briefly each time ignition is turned to RUN position, fuel pump circuit is okay. If fuel pump does not run, go to step 2).

2) Check For VPWR To ECA Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between test pins No. 37 and 40 at breakout box. Measure voltage between test pins No. 57 and 60 at breakout box. If both voltage readings are more than 10.5 volts, go to step 3). If voltage is 10.5 volts or less, go to CIRCUIT TEST B, step 1).

3) Check Voltage To POWER-TO-PUMP Circuit With ignition on, measure voltage between chassis ground and POWER-TO-PUMP circuit at fuel pump relay while cranking engine. If reading is less than 8 volts, go to step 4). If reading is 8 volts or more, check fuse to fuel pump relay. If fuse is okay, repair open in BATT+ circuit between fuel pump relay and battery positive terminal. Remove breakout box, and repeat QUICK TEST.

4) Checking BATT (+) Circuit To Fuel Pump Relay Turn ignition on. Leave breakout box installed and ECA connected. Locate fuel pump relay. Measure voltage between chassis ground and BATT (+) circuit at fuel pump relay. If voltage is less than 10.5 volts, repair open in BATT (+) circuit between fuel pump relay and positive battery terminal. Repeat QUICK TEST. If reading is 10.5 volts or more, go to step 5).

5) Check Voltage At POWER-TO-PUMP Circuit Turn ignition off. Connect jumper wire from test pin No. 22 to test pin No. 40 or 60 at breakout box. Turn ignition on. Measure voltage between chassis ground and POWER-TO-PUMP circuit at fuel pump relay. If voltage is 10.5 volts or more, replace ECA and repeat QUICK TEST. If voltage is less than 10.5 volts, replace fuel pump relay, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 5) to step 7). No test procedures have been omitted.

7) Code 87/556: Check VPWR To Fuel Pump Relay Code 87/556 indicates a fuel pump primary circuit failure. Possible causes for this fault are

1. Inertia switch not reset or circuit open.
2. Open or shorted circuit.
3. Faulty fuel pump relay.
4. Faulty ECA.

Disconnect fuel pump relay. Turn ignition on. Measure voltage between chassis ground and VPWR circuit at fuel pump relay wiring harness connector. If reading is 10.5 volts or more, go to step 8). If reading is less than 10.5 volts, verify inertia switch is in ON position. If switch is okay, repair open in VPWR circuit between EEC power relay and fuel pump relay. Connect fuel pump relay and repeat QUICK TEST.

8) Check Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. (Scheme 109) Set DVOM on 200-ohm scale. On Bronco, Pickup and Van relays, measure resistance between terminals No. 85 and 86. On all other relays, measure resistance between VPWR pin and FUEL PUMP circuit pin at fuel pump relay. Both resistances should be 40-85 ohms. Set DVOM to 20-k/ohm scale. On Bronco, Pickup and Van relays, measure resistance between terminal No. 85 and terminals No. 30 and 87. On all other relays, measure resistance between FUEL PUMP circuit pin and both POWER-TO-PUMP and BATT (+) pins at fuel pump relay. All resistances should be greater than 10,000 ohms. If resistances are as specified, go to step 9). If resistances are not as specified, replace fuel pump relay and repeat QUICK TEST.

Fuel Pump Relay Connector Terminal ID. Scheme 109

9) Check For Short To Power Turn ignition off. Disconnect fuel pump relay. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 22 and negative battery terminal. If voltage is less than 1.0 volt, go to step 10). If voltage is 1.0 volt or more, repair short circuit. Reconnect ECA, and attempt to start vehicle. If vehicle fails to start, replace ECA. Repeat QUICK TEST.

10) Check For Shorts To Ground Turn ignition off. Leave fuel pump relay disconnected. Measure resistance between test pin No. 22 and test pins No. 40 and 60. If resistance is less than 10,000 ohms, repair short in FUEL PUMP circuit. Remove breakout box, and repeat QUICK TEST. If resistance is 10,000 ohms or more, go to step 11).

11) Check Fuel Pump Circuit Continuity Turn ignition off. Leave fuel pump relay disconnected. Measure resistance between FUEL PUMP circuit at fuel pump relay wiring harness connector and test pin No. 22 at breakout box. If resistance is less than 5 ohms, replace ECA and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit. Reconnect all components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.

20) Code 95/542 A KOEO Code 95/542 indicates one of following conditions

Engine 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. HEGO short to power (dual HEGO applications).
5. Faulty ECA.

No Start

1. Inertia switch not reset or electrically open.
2. Open circuit in or between ECA and fuel pump.
3. Faulty ground connection at fuel pump.

If engine starts, go to step 21). If engine does not start, go to step 24).

21) Check Fuel Pump Operation Turn ignition on. Wait 5 seconds. Listen for fuel pump operation. If fuel pump is off, go to step 23). If fuel pump is on, go to step 22).

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 repeat QUICK TEST. If fuel pump is on with relay disconnected, repair short to power in POWER-TO-PUMP/FPM circuit. (For models with relay block, also check fuel pump prime plug circuit). Repeat QUICK TEST.

23) Check Continuity Of Fuel Pump Monitor (FPM) Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect and repair any damaged terminals. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect fuel pump relay. Measure resistance between test pin No. 8 at breakout box and POWER-TO-PUMP circuit at fuel pump relay wiring harness connector. If resistance is less than 5 ohms, go to step 35) (dual HEGO) or replace ECA and repeat QUICK TEST (single HEGO). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

24) Check Inertia Switch Turn ignition off. Disconnect fuel pump inertia switch. Ensure switch is reset. Measure resistance of inertia switch. If resistance is less than 5 ohms, reconnect switch and check for open in POWER-TO-PUMP circuit, poor fuel pump ground or open in fuel pump. If resistance is 5 ohms or more, reset or replace inertia switch. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 30). No test procedures have been omitted.

30) Code 96/543 Code 96/543 indicates fuel pump secondary circuit failure between BATT (+) supply and FPM connection to POWER-TO-PUMP circuit. Following are possible causes

1. Open circuit between BATT (+) supply and FPM connection to POWER-TO-PUMP circuit.
2. Fuel pump relay contacts are always open.

1. HEGO short to power (dual HEGO models).
2. Faulty ECA.

If engine starts, go to step 35) (dual HEGO) or replace ECA and repeat QUICK TEST (single HEGO). If engine does not start, go to step 31).

31) Check For BATT (+) To Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. Connect DVOM between BATT (+) terminal at fuel pump relay wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, go to step 32). If voltage is less than 10.5 volts, check fuse/fusible link for BATT (+) supply to fuel pump relay. If fuse/fusible link is okay, repair open circuit in BATT (+) circuit. Repeat QUICK TEST.

32) Check POWER-TO-PUMP Circuit Continuity Turn ignition off. With fuel pump relay disconnected, measure resistance between POWER-TO-PUMP terminal at fuel pump relay wiring harness connector and negative battery terminal. If resistance is less than 10 ohms, replace fuel pump relay. Reconnect relay and repeat QUICK TEST. If resistance is 10 ohms or more, repair open circuit in POWER-TO-PUMP circuit between FPM splice and fuel pump relay. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 32) to step 35). No test procedures have been omitted.

Due to internal circuitry of ECA, a left/front HEGO signal short to power could produce a Code 95/542 or 96/543.

35) Check Left/Front HEGO Sensor For Short To Power Turn ignition off. Disconnect left or front HEGO sensor. (Scheme 110) Measure resistance between HEGO SIGNAL terminal and KEY POWER terminal at HEGO sensor wiring harness connector. (Scheme 111) If resistance is 10,000 ohms or more, go to step 36). If resistance is less than 10,000 ohms, replace HEGO sensor. Clear KAM, and repeat QUICK TEST.

HEGO Sensor Connector. Scheme 110

HEGO Sensor Vehicle Harness Connector. Scheme 111

36) Check HEGO Circuit For Short To Power Turn ignition off. Disconnect ECA. Inspect and repair any damaged terminals. Turn ignition on. With left or front HEGO sensor disconnected, measure voltage between HEGO SIGNAL at HEGO wiring harness connector and chassis ground. If voltage is less than 2 volts, replace ECA and repeat QUICK TEST. If voltage is 2 volts or more, repair short circuit. Reconnect ECA and HEGO sensor. Clear KAM, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 36) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 95/542 Code 95/542 indicates one of following conditions

1. Faulty ground circuit at fuel pump.
2. FPM or POWER-TO-PUMP circuit short to power.
3. Fuel pump relay contacts stuck closed.
4. Open circuit in or between fuel pump and FPM circuit at ECA.
5. Left or front HEGO circuit short to power (dual HEGO system).
6. FUEL PUMP circuit is activated at a time that is not programmed into ECA strategy.

Start engine, and enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Check for engine miss or intermittent fuel pump deactivation while performing following

1. Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and fuel pump.
2. Shake and bend fuel pump ground circuit between fuel pump and ground.
3. Lightly tap fuel pump to simulate road shock.
4. Lightly tap inertia switch to simulate road shock.

With ignition off, check harness connectors for corrosion and damage. Isolate and repair any faults. Clear continuous memory, and repeat QUICK TEST. If no faults are found, go to step 91).

91) Check FPM Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Connect test light between test pin No. 8 and test pin No. 37 at breakout box. With test light on, perform wiggle test on FPM circuit between fuel pump and ECA. Light will go out if fault is found, indicating an open circuit. If a fault is found, repair as necessary and repeat QUICK TEST. If no fault is found, go to step 92).

92) Check For Shorts To Power Connect a test light between breakout box test pin No. 8 and test pin No. 40. Test light should be off. Observe test light while bending and shaking FPM circuit and POWER-TO-PUMP circuit. Lightly tap fuel pump relay to simulate road shock. Fault is indicated if test light comes on. Isolate and repair fault as necessary, and repeat QUICK TEST. If no fault is found, go to step 96) (dual HEGO) or step 99) (single HEGO).

93) Continuous Memory Code 96/543: Check For Continuous Memory Code 87/556 If Code 87 or 556 is present, go to step 95). If Codes 87 and 556 are not displayed, go to step 94).

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 between fuel pump relay to FPM splice (if applicable).
4. Left/front HEGO circuit short to power (dual HEGO).

Start engine. Check for engine miss or intermittent fuel pump deactivation while performing following

1. Shake and bend BATT (+) circuit wiring harness between power source and fuel pump relay.
2. Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and FPM splice (if applicable).
3. Lightly tap fuel pump relay to simulate road shock.

Turn ignition off. Inspect all fuel pump relay and BATT (+) connectors for damage and corrosion. If fault is found, repair as necessary. Clear and repeat QUICK TEST. If no fault is found, a Continuous Memory Code 95/543 may have been set without a Continuous Memory Code 87/556 under certain conditions, even though a fault has occurred in fuel pump primary circuit. Go to step 95) for fuel pump primary circuit check.

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

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. Check for engine miss or intermittent fuel pump deactivation while performing following

1. Shake and bend VPWR circuit wiring harness between EEC and fuel pump relay.
2. Shake and bend FP circuit wiring harness connector between fuel pump relay and ECA.
3. Lightly tap fuel pump relay to simulate road shock.
4. Lightly tap inertia switch to simulate road shock (if equipped).

Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. If fault is found, isolate and repair as necessary. Repeat QUICK TEST. If no faults are found but Code 96/543 is present, go to step 96) (dual HEGO). If fault can not be duplicated at this time, go to step 99) (single HEGO).

Due to internal circuitry of ECA, an intermittent left/front HEGO signal short to power could produce a Continuous Memory Code 95/542 or 96/543.

96) Check Left/Front HEGO Circuit For Short To Power Turn ignition off. Breakout box should be installed with ECA disconnected. Connect test light between left/front HEGO test pin and pin No. 40 at breakout box. Test light should be off. Observe test light while bending and shaking left/front HEGO circuit from HEGO sensor to ECA. Lightly tap HEGO SENSOR to simulate road shock. Fault is indicated if test light comes on. Isolate and repair as necessary. Clear Keep-Alive Memory (KAM), and repeat QUICK TEST. If no fault is indicated, go to step 99).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 96) to step 99). No test procedures have been omitted.

99) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a driveability or MIL light symptom. To prepare for road test

1. Install fuel pressure gauge.
2. Install MAP/BP tester.
3. Disconnect ECA 60-pin connector, install breakout box and reconnect ECA to breakout box.
4. Connect "T" vacuum gauge into manifold vacuum line.
5. Have DVOM, writing materials and appropriate schematics and pin voltage charts available.

With ignition on and negative lead of DVOM connected to negative battery terminal, ensure following signals are correct

1. POWERS: KAPWR (pin No. 1) is greater than 10.5 volts, VPWR (pins No. 37 and 57) is greater than 10.5 volts and VREF (pin No. 26) is 4-6 volts.
2. GROUNDS: PWR GND (pins No. 40 and 60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0.0-0.5 volt.
3. OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. Step 20) and MAF RTN (pin No. 9 or 15) are 0.0-0.5 volt.

Test lights and DVOM are useful during diagnosis. For example: with Continuous Memory Code 87/556 (fuel pump primary circuit failure) and a surge or stall symptom, connect a test light to fuel pump relay between VPWR and ground. Connect DVOM between FP circuit at fuel pump relay and breakout box test pin No. 1. Under normal driving conditions, test light will be on and DVOM will read battery voltage. If vehicle stalls, ECA will open FP circuit and DVOM voltage will be low. If fault is in fuel pump circuit, test light and DVOM status will change as fault occurs. If test light at VPWR circuit goes out, fault is in VPWR circuit to fuel pump relay. If test light and DVOM status do not change and Continuous Memory Code 87/556 is set again, replace fuel pump relay. If only FP voltage goes low, fault is in FP circuit or ECA. To diagnose FP circuit and ECA, connect DVOM between breakout box test pin No. 1 and 22. If voltage goes low as symptom occurs, replace ECA. If voltage stays high as symptom occurs, fault is in FP circuit. For fuel pump secondary circuit Codes 95/542 and 96/543, circuits BATT (+), POWER-TO-PUMP and FPM can be diagnosed using same procedure. Drive vehicle and attempt to induce symptom. Information provided by vehicle operator may help when trying to recreate symptom. When symptom occurs, assistant should observe and record changes in voltage signals. Information about symptom and operating condition value of voltage signal and any other information available should be recorded for analysis. If unable to duplicate symptom during road test, verify EEC-IV values are within acceptable range. After test is completed, analyze results to locate and repair fault causing symptom. If problem cannot be identified, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes of symptom.

Perform this test when instructed by QUICK TEST. To prevent replacement of good components, be aware following non-EEC related areas may be at fault

1. Damaged vacuum hoses.
2. Damaged Backpressure Transducer (BPT).
3. EGR valve.
4. EVP sensor.

This test is only intended to diagnose

1. EVR solenoid.
2. ECA.
3. EVR and VPWR harness circuits.

EVR solenoid regulate vacuum to EGR valve by way of Backpressure Transducer (BPT). When energized, EVR opens a port between manifold vacuum and EGR valve. When not energized, EVR closes port to EGR and vacuum is vented to atmosphere.

EGR Valve Regulator (EVR) Solenoid Ckts. & Connector Terminal ID. Scheme 112

1) Code 558 Code 558 indicates failure in EVR solenoid circuit. Possible causes for this fault are

1. Faulty EVR solenoid.
2. Faulty vacuum hoses.
3. Open or ground circuit in wiring harness.
4. Faulty ECA.

Turn ignition off. Remove scan tester (if applicable). Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at Self-Test connector. Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at Self-Test connector. (Scheme 89)and (Scheme 90) in CIRCUIT TEST B. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage does not increase, fully apply throttle and release. If STO voltage remains low, go to CIRCUIT TEST QC. If voltage increases, remain in OUTPUT STATE CHECK and go to step 2).

2) Check EVR Solenoid Electrical Turn ignition off. Disconnect EVR solenoid wiring harness connector. Connect DVOM positive lead to VPWR terminal and negative test lead to EVR terminal at EVR solenoid wiring harness connector. Depress and release throttle 3-5 times to cycle solenoid output. If EVR solenoid voltage output change is 0.5 volt or more, go to step 3). If EVR solenoid voltage output change is less than 0.5 volt, go to step 5).

3) Check EVR Solenoid Vacuum Turn ignition on. Disconnect EVR solenoid vacuum hoses. Install vacuum pump on EVR solenoid vacuum source port. Install vacuum gauge on solenoid output port. Apply 6 in. Hg, and hold. Depress and release throttle 3-5 times to cycle solenoid output. Turn ignition off. If vacuum gauge shows vacuum cycling at output port, go to step 4). If vacuum gauge does not show vacuum cycling at output port, replace EVR solenoid and repeat QUICK TEST.

4) Check EVR Vacuum Hoses Remove jumper wire, vacuum pump and gauge. Remove vacuum hoses individually. Plug one end of hose. Connect vacuum pump at opposite end. Apply vacuum and observe gauge. If vacuum is not held, replace hose and repeat QUICK TEST. If vacuum is held, ensure vacuum port between BPT and EGR is not restricted. If vacuum port is clear, go to step 5).

5) Check EVR Solenoid VPWR Turn ignition off. Disconnect EVR solenoid wiring harness connector. Turn ignition on. Measure voltage between VPWR at EVR solenoid wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, go to step 6). If voltage is less than 10.5 volts, repair open VPWR circuit and repeat QUICK TEST.

6) Check EVR Solenoid Circuit Continuity Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between EVR terminal at EVR solenoid wiring harness connector and test pin No. 31. If reading is less than 5 ohms, go to step 7). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

7) Check EVR Solenoid Circuit For Short Turn ignition off. Measure resistance between test pin No. 31 and test pins No. 37 and 57 at breakout box. If each resistance is 10,000 ohms or more, replace ECA and repeat QUICK TEST. If reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.

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

1. AM1 or AM2 solenoid valve assembly.
2. Wiring harness circuits (AM1, AM2 and VPWR).
3. Vacuum supply.
4. ECA.

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

1. Thermactor air system drive belt, air pump and valve.
2. Blocked or restricted thermactor air passages in engine.

CIRCUIT TEST KC TEST PIN WIRE COLOR ID

Air Management Circuits. Scheme 113

1) Codes 44/311, 45/312, 46/313 & 94/314 Code 44/311 or 94/314 indicates thermactor system is inoperative. Code 45/312 indicates thermactor air is incorrectly routed. Code 46/313 indicates thermactor air is not by-passed when directed. Possible causes for these faults are

1. Vacuum hoses leaking, blocked or kinked.
2. Air pump or diverter valve inoperative.
3. Air Management (AM) solenoid defective or blocked.

Check for correct vacuum hose routing to AM1/AM2 solenoids and by-pass diverter valve. See Vehicle Emission Control Information (VECI) label. Check for kinked disconnected, or blocked vacuum hoses. Check for kinked or blocked air hoses. If faults are detected, repair as necessary and repeat QUICK TEST. If no faults are detected and Code 44/311 or 94/314 is present, go to step 4).If Code 46/313 is present, go to step 3). If Code 45/312 is present, go to step 2).

2) Attempt To Eliminate Code 45/312 Disconnect and plug vacuum hose at diverter valve. Turn ignition off. Repeat KOER SELF-TEST, and record codes. If Code 45/312 is present, EEC-IV system is okay. Inspect diverter valve and check valve for faults. If Code 45/312 is not present, go to step 4).

3) Attempt To Eliminate Code 46/313 Disconnect and plug vacuum hose at by-pass valve. Turn ignition off. Repeat KOER SELF-TEST, and record codes. If Code 46/313 is present, EEC-IV system is okay. Check by-pass valve for problem. If Code 46/313 is not present, go to step 4).

4) Output Check Enter OUTPUT STATE CHECK. See ADDITIONAL SYSTEM FUNCTIONS. Use only a VOM or DVOM for this step. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo (if equipped). With DVOM on 20-volt scale, connect DVOM negative lead to STO terminal at self-test connector. Connect positive lead to positive battery terminal. Using jumper wire, connect STI to SIG RTN at self-test connector. (Scheme 89)and (Scheme 90) in CIRCUIT TEST B. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to step 5). If voltage does not increase, depress throttle to WOT and release. If STO voltage does not go high, go to CIRCUIT TEST QC.

5) Check Solenoid Electrical Operation Set DVOM on 20-volt scale. Disconnect AM solenoids. Connect DVOM positive lead to VPWR terminal and negative lead to AM1 terminal at AM1 solenoid wiring harness connector. While observing DVOM, depress and release throttle several times to cycle output on and off. Repeat test for AM2 solenoid. Connect DVOM positive lead to VPWR terminal and negative test lead to AM2 terminal on AM2 solenoid wiring harness connector. Cycle AM2 solenoid on and off. If either solenoid does not cycle more than 0.5 volt, remove jumper and go to step 9). If both solenoids cycle more than 0.5 volt, stay in OUTPUT STATE CHECK, reconnect solenoids and go to step 6).

6) Check Solenoids For Vacuum Cycling Connect vacuum pump to AM1 solenoid vacuum supply port. Connect vacuum gauge to output port. Maintain vacuum at source while depressing and releasing throttle to cycle output on and off. Observe vacuum gauge. Repeat for AM2 solenoid. If either output does not cycle on and off, replace solenoid assembly and repeat QUICK TEST. If both outputs cycle on and off, exit OUTPUT STATE CHECK and go to step 7).

7) Check Solenoids For Internal Vacuum Leaks Connect a vacuum pump to AM1 solenoid supply port. Connect a vacuum gauge to AM1 solenoid output port. Apply 15 in. Hg vacuum and observe gauge. Repeat test for AM2 solenoid. If vacuum gauge reading holds vacuum for each solenoid, check vacuum source for blockage and leakage from manifold to solenoids and control valves. If vacuum source is okay, inspect thermactor air tube and air passages in cylinder head for carbon blockage. Repeat QUICK TEST. If vacuum gauge does not hold vacuum, replace solenoid assembly and repeat QUICK TEST.

8) Codes 81/553 & 82/552: Check VPWR Circuit Voltage Codes81/553 and 82/552 indicate voltage output for thermactor air solenoid did not change when activated. Possible causes for this fault are

1. Shorted or open circuits.
2. Solenoid resistance out of range.
3. Faulty ECA.

Disconnect both solenoid connectors. Turn ignition on. Measure voltage between VPWR terminal of wiring harness connector and battery ground for both solenoids. If either voltage reading is less than 10.5 volts, repair wiring harness open circuit. Connect solenoid connectors, and repeat QUICK TEST. If both readings are 10.5 volts or more, go to step 9).

9) Measure Solenoid Resistance Turn ignition off. Set DVOM on 200-ohm scale. Disconnect AM1 and AM2 solenoid connectors. Measure resistance of both solenoids. If either resistance is not 50-100 ohms, replace solenoid assembly and repeat QUICK TEST. If both resistances are 50-100 ohms, go to step 10).

10) Check Circuit Continuity Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 51 and AM1 terminal at wiring harness connector. Measure resistance between test pin No. 11 and AM2 terminal at wiring harness connector. If either resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If both resistances are less than 5 ohms, go to step 11).

11) Check For Short To Ground Turn ignition off. Measure resistance between breakout box test pin No. 51 and pins No. 40, 46 and 60. Measure resistance between test pin No. 11 and test pins No. 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short to ground and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to step 12).

12) Check For Shorts To Power Circuit Turn ignition off. Measure resistance between breakout box pin No. 51 and test pins No. 37 and 57. Also measure resistance between test pin No. 11 and test pins No. 37 and 57. If any resistance is less than 10,000 ohms, repair short to power and repeat QUICK TEST. If code is repeated, replace ECA. If all resistances are 10,000 ohms or more, replace ECA, and repeat QUICK TEST.

Perform this test when instructed by QUICK TEST or if 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 114

CIRCUIT TEST KD TEST PIN WIRE COLOR ID

1) Check System Function Use only VOM or DVOM for this step. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at self-test connector. Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at self-test connector. (Scheme 89)and (Scheme 90) in CIRCUIT TEST B. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to step 2). If voltage does not increase, apply full throttle and release. If STO voltage does not increase, leave test equipment hooked up and go to CIRCUIT TEST QC.

2) Check CANP Solenoid Electrical Function Turn ignition on. Disconnect CANP solenoid. Connect DVOM positive test lead to VPWR terminal and negative test lead to CANP terminal at solenoid wiring harness connector. While observing DVOM, depress and release throttle several times to cycle output on and off. If CANP circuit voltage does not cycle 0.5 volt or more, remove jumper wire and go to step 6). If CANP circuit voltage cycles, remain in OUTPUT STATE CHECK and go to step 3).

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 vacuum 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 or hoses. If CANP holds vacuum for 20 seconds, remain in OUTPUT STATE CHECK, leave vacuum pump attached and go to step 4).

4) Check Solenoid Mechanical Operation Connect CANP solenoid connector. Apply 16 in. Hg vacuum to manifold vacuum side of CANP solenoid. 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 step 5). 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 Or 569: Check CANP Solenoid Resistance Code85/565 or 569 indicates fault in CANP solenoid circuit. For vehicles with dual CANP systems, Code 565 refers to CANP 1; Code 569 refers to CANP 2. Possible causes for this fault are

1. Faulty CANP solenoid.
2. Open in wiring harness circuit.
3. Shorted wiring harness circuit.
4. Faulty ECA.

Turn ignition off. Set DVOM on 200-ohm scale. Disconnect CANP solenoid connector. Measure CANP solenoid resistance. If resistance is 40-90 ohms, go to step 7). If resistance is not 40-90 ohms, replace CANP solenoid and repeat QUICK TEST.

7) Check Voltage Of VPWR Circuit With CANP solenoid disconnected, turn ignition on. Measure voltage between VPWR terminal at CANP solenoid harness connector and negative battery terminal. If resistance is 10.5 volts or more, go to step 8). If resistance is less than 10.5 volts, repair open circuit and repeat QUICK TEST.

8) Check Continuity Of CANP Circuit Turn ignition off. Disconnect CANP solenoid. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 31 and CANP terminal at solenoid wiring harness connector. If resistance is less than 5 ohms, go to step 9). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

9) Check CANP Circuit For Short To Ground Turn ignition off. With CANP solenoid disconnected, measure resistance between test pin No. 31 and pins No. 40, 46 and 60 at breakout box. If all resistances are 10,000 ohms or more, go to step 10). If any resistance is less than 10,000 ohms, repair short to ground and repeat QUICK TEST.

10) Check CANP Circuit For Short To Power Turn ignition off. With CANP solenoid disconnected, measure resistance between test pin No. 31 and test pins No. 37 and 57 at breakout box. If all resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST. If any resistance is less than 10,000 ohms, repair circuit short to power and repeat QUICK TEST. If code is repeated, replace ECA and repeat QUICK TEST.

Perform this test when instructed by QUICK TEST or if 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 terminals intended to diagnose

1. RPM during SELF-TEST mode.
2. ISC solenoid.
3. Wiring harness circuits (ISC and VPWR).
4. ECA.

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

1. Engine temperature under or over correct operating range.
2. A/C input (electrical problem).
3. Incorrect idle speed or throttle stop adjustment.
4. Faulty cruise control linkage.

Idle Speed Control (Air By-Pass) Circuit. Scheme 115

CIRCUIT TEST KE TEST PIN WIRE COLOR ID

1) Code 12/412 Or 16 Code 12/412 indicates engine RPM could not be controlled within upper RPM limit during KOER SELF-TEST. Code 16 indicates engine RPM was too low to perform HEGO test during KOER SELF-TEST. Possible causes for this fault are

1. Open or shorted circuit.
2. Sticking or binding throttle linkage.
3. Incorrect idle airflow setting.
4. Throttle body or ISC solenoid contaminated.
5. Faulty ISC solenoid.
6. Faulty ECA.
7. Mechanical faults unrelated to EEC-IV which could affect RPM.

Turn ignition off. Connect tachometer to engine. Start engine. Disconnect Idle Speed Control (ISC) harness. If RPM drops or engine stalls, go to step 2). If RPM does not drop or engine does not stall, go to step 3).

2) Check For EGR Codes If EGR service Code 31/327, 32/326/328, 33/332, 34/336/334 or 213 is displayed, reconnect ISC solenoid. Go to appropriate KOER SELF-TEST. See SERVICE CODE REFERENCE CHARTS. If these codes are not displayed, go to step 3).

3) Check For Other EEC-IV Codes If Code 22/126, 41/172, 42/173, 91/136 or 92/137 is displayed, reconnect ISC solenoid. Go to appropriate KOER SELF-TEST. See SERVICE CODE REFERENCE CHARTS. If these codes are not displayed, go to step 4).

4) Measure ISC Solenoid Resistance Turn ignition off. Disconnect ISC solenoid. Connect DVOM positive lead to VPWR terminal and negative lead to ISC terminal. (Scheme 116) Measure resistance of ISC solenoid. If resistance is not 6-13 ohms, replace ISC solenoid and repeat QUICK TEST. If resistance is 6-13 ohms, go to step 5).

ISC Solenoid Connector. Scheme 116

5) Check For Internal Short To ISC Solenoid Case Turn ignition off. With ISC solenoid disconnected, measure resistance from either ISC terminal pin to ISC solenoid housing. If resistance is more than 10,000 ohms, go to step 6). If resistance is 10,000 ohms or less, replace ISC solenoid. Repeat QUICK TEST.

6) Check VPWR Circuit Voltage Leave ISC harness disconnected. Turn ignition on. Measure voltage between VPWR terminal at ISC harness connector and battery ground terminal. If voltage is 10.5 volts or more, go to step 7). If voltage is less than 10.5 volts, repair open in circuit and repeat QUICK TEST.

7) Check ISC Circuit Continuity Turn ignition off. Leave ISC solenoid disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 21 and ISC terminal at ISC wiring harness connector. If resistance is 5 ohms or less, go to step 8). If resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST.

8) Check ISC Circuit For Short To Ground Turn ignition off. Leave ISC solenoid disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short to ground and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to step 9).

9) Check ISC Circuit For Short To Power Turn ignition on. Measure voltage between breakout box test pin No. 21 and chassis ground. If voltage is more than 1.0 volt, repair short circuit. Reconnect all components, and repeat QUICK TEST. If code or symptom is still present, replace ECA. If voltage is 1.0 volt or less, go to step 10).

10) Check ISC Signal From ECA Turn ignition off. Reconnect ISC solenoid. Connect ECA to breakout box. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40 at breakout box. Start engine. Observe DVOM while slowly increasing engine speed to 3000 RPM. If DVOM voltage reading is 3.0-11.5 volts, go to step 11). If DVOM voltage reading is not 3.0-11.5 volts, remove ISC solenoid to confirm that it is not open. If ISC is okay, replace ECA and repeat QUICK TEST.

11) Check Base Idle Verify base idle speed is correct. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section. If base idle speed is within specification, remove ISC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is still present, replace ISC solenoid. If base idle speed is not correct, reset idle speed to specification. Repeat QUICK TEST. If unable to set idle to specification, go to step 12).

12) Check For 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 Vehicle Emission Control Information (VECI).
4. Check for leaks around ISC solenoid (gaskets, etc.).

If all of these items are okay, remove ISC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is still present, replace ISC solenoid. If any of these items are faulty, service as necessary. Remove breakout box. Reconnect components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 15). No test procedures have been omitted.

15) Code 13/411 Code 13/411 indicates engine RPM could not be controlled within lower RPM limit during KOER SELF-TEST. Possible causes for this fault are

1. Incorrect idle airflow setting.
2. Vacuum leaks.
3. Sticking or binding throttle linkage.
4. Throttle plates open.
5. Incorrect ignition timing (TFI ignition only).
6. Throttle body or ISC solenoid contamination.
7. ISC circuit shorted to ground.
8. Faulty ISC solenoid.

If above items are okay and idle is set to specification, remove ISC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is present, replace ISC solenoid. If idle speed is not set to specification, reset and repeat QUICK TEST. If idle speed cannot be set to specification, go to next step.

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

1. Vacuum hoses. Check Vehicle Emission Control Information (VECI).
2. Throttle linkage and/or cruise control linkage (sticking or binding).
3. Induction system (vacuum leaks).
4. Throttle body (contamination).
5. Ensure throttle plates are fully closed.
6. Ensure CANP solenoid is not stuck open.
7. Ensure base ignition timing is to specification on emission decal (TFI vehicles only).

If above items are okay, go to step 17). If fault is found, service as necessary and repeat 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 resistance is more than 10,000 ohms, go to step 18). If resistance is 10,000 ohms or less, replace ISC solenoid. Repeat QUICK TEST.

18) Check ISC Circuit For Short To Ground Turn ignition off. Leave ISC solenoid disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box(T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short to ground. Reconnect components, and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to step 19).

19) Check ISC Signal From ECA Turn ignition off. Connect ECA to breakout box. Reconnect ISC solenoid. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40. Start engine. Observe DVOM while slowly increasing and decreasing engine RPM. If voltage is 3.0-11.5 volts, remove ISC solenoid and inspect for contamination. Repair or replace as necessary, and repeat QUICK TEST. If code or symptom is still present, replace ISC solenoid. If voltage is not 3.0-11.5 volts, replace ECA and repeat 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. Low ambient temperature (less than 45°F).

This test is only intended to diagnose

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

WOT A/C Cut-Out Circuit. Scheme 117

CIRCUIT TEST KM TEST PIN WIRE COLOR ID

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. Turn ignition off. Disconnect A/C clutch wiring harness connector. Turn A/C switch to A/C position. Start engine, and wait 10 seconds. Measure voltage between power side of A/C clutch wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, EEC-IV system is okay. Check 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. Disconnect A/C clutch and WAC relay wiring harness connectors. Measure resistance between power side of A/C clutch wiring harness connector and POWER-TO-CLUTCH terminal at WAC relay wiring harness connector. If resistance is 5 ohms or less, reconnect A/C clutch and go to step 3). If resistance is more than 5 ohms, repair open circuit and retest system.

3) Check For Power On A/C Demand Circuit Turn ignition on. Turn A/C switch on. Set DVOM to 20-volt scale. Measure voltage between A/C demand input terminal at WAC relay wiring harness connector and chassis ground. If voltage is 10.5 volts or more, go to step 5). If voltage is less than 10.5 volts, verify operation of A/C clutch cycling pressure switch and A/C demand switch. If components are okay, repair open circuit and reconnect all components. Recheck system.

4) Check Continuity Between WAC Relay & A/C Relay Turn ignition off. Disconnect WAC and A/C relays. Set DVOM on 200-ohm scale.Measure resistance between A/C relay output to WAC relay circuit at A/C relay wiring harness connector and A/C relay input at WAC relay wiring harness connector. If resistance is less than 5 ohms, reconnect WAC relay and check A/C system. If resistance is 5 ohms or more, repair open circuit. Connect relays, and check system operation.

5) Check WAC Circuit For Short To Ground Turn ignition off. Disconnect 60-pin ECA connector. Disconnect WAC relay. Inspect wiring, and repair if damaged. Measure resistance between WAC terminal at WAC relay and chassis ground. If resistance is less than 10,000 ohms, repair short and recheck system operation. If resistance is 10,000 ohms or more, go to step 6).

6) Check For Voltage At ACCS Input To ECA Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set A/C switch to A/C position. Turn ignition on. Measure voltage between test pins No. 10 and 40 at breakout box. If voltage is 10.5 volts or less, repair open circuit. Connect all components, and check system operation. If voltage is more than 10.5 volts, go to step 7).

7) Check WAC Relay Turn ignition off. Connect WAC relay, leaving A/C clutch disconnected. Turn ignition on. Set A/C switch to A/C position. Measure voltage between power side of A/C clutch wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, replace ECA. If voltage is less than 10.5 volts, replace WAC relay.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 15). No test procedures have been omitted.

15) No A/C Output At WOT: Enter Output State Check Use only VOM or DVOM for this step. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at self-test connector. Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at self-test connector. (Scheme 121)in CIRCUIT TEST QA. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases to 10.5 volts or more, remain in OUTPUT STATE CHECK and go to step 16). If voltage does not increase to 10.5 volts, depress throttle to WOT and release. If STO voltage does not go high, leave test equipment connected and go to CIRCUIT TEST QC, step 2).

16) Check For VPWR To Relay With vehicle in OUTPUT STATE CHECK, disconnect wiring harness from WAC relay. Measure voltage between VPWR circuit at WAC relay wiring harness connector and chassis ground. If voltage is less than 10.5 volts, repair open in VPWR circuit between EEC power relay and WAC relay. Remove test equipment, and retest system. If voltage is 10.5 volts or more, go to step 17).

17) Check WAC System For Cycling Leave vehicle in OUTPUT STATE CHECK. Disconnect WAC relay wiring harness connector. Connect DVOM positive test lead to VPWR circuit and connect negative test lead to WAC circuit at WAC relay wiring 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. If voltage does not cycle, remove test leads. Reconnect speed control servo, and go to step 18).

18) Check Continuity Of WAC Circuit Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 54 and WAC terminal at WAC relay wiring harness connector. If resistance is 5 ohms or more, repair open circuit. Reconnect all components, and retest system. If resistance is less than 5 ohms, go to step 19).

19) Check WAC Circuit For Short To Power Turn ignition off. Leave ECA and WAC relay disconnected. Turn ignition on. Measure voltage between test pin No. 54 and chassis ground. If voltage is 1.0 volt or less, replace ECA and retest system. If voltage is more than 1.0 volt, repair short circuit. If symptom is still present, replace ECA.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 19) to step 30). No test procedures have been omitted.

30) Cycle A/C Demand Switch Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Connect DVOM negative test lead to test pin No. 40 and positive test lead to test pin No. 43. Turn ignition on. Cycle A/C switch. If voltage goes high and low as switch is cycled, go to step 43). If voltage does not cycle, go to step 31).

31) Check Continuity Of A/C Demand (ACD) Circuit Turn ignition off. Measure resistance between test pin No. 43 at breakout box and A/C Demand switch. If resistance is more than 5 ohms, repair open in ACD circuit and repeat QUICK TEST. If resistance is 5 ohms or less, EEC-IV system is okay. Remove breakout box, and reconnect components. Fault is in A/C system.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 31) to step 35). No test procedures have been omitted.

35) Check A/C Demand Circuit For Short To Power Turn ignition off. Disconnect WAC relay (except 4.9L). Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. With A/C Demand switch in OFF position, turn ignition on. Measure voltage between chassis ground and test pin No. 43 at breakout box. If voltage is 1.0 volt or less, EEC-IV system is okay. Fault is in A/C system. If voltage is more than 1.0 volt, check operation of A/C Demand switch. If switch operation is okay, repair short circuit and retest system.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 35) to step 40). No test procedures have been omitted.

Before entering this test, ensure A/C selector is in OFF position and shift selector is in PARK position (AXOD-E and E4OD vehicles). If A/C was on, repeat QUICK TEST. If Code 67 or 79/539 is present, continue with this test.

40) Check A/C Input Code 79/539 indicates ACCS input to ECA was high during SELF-TEST. Code 67 indicates Neutral Drive Switch (NDS) or ACCS circuit voltage was high during SELF-TEST. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM to 20-volt scale. Turn ignition on. Measure voltage between test pin No. 10 at breakout box and chassis ground. If voltage is 1.0 volt or more, repair short to power in A/C circuit and repeat QUICK TEST. If voltage is less than 1.0 volt, go to step 41) for vehicles with 2-digit codes and E4OD transmission. On all other vehicles, replace ECA and repeat QUICK TEST.

41) Check For Short To Power In ECA Turn ignition off. Disconnect A/C clutch connector. Set DVOM to 20-volt scale. Turn ignition on. Measure voltage between test pins No. 10 and 40 at breakout box. If voltage is 5 volts or more, replace ECA and repeat QUICK TEST. If voltage is less than 5 volts, go to CIRCUIT TEST TD.

A low idle with A/C on may be caused by ECA not receiving or recognizing A/C input from pin No. 10

42) Check A/C Input Circuit Turn A/C switch to A/C position. Perform KOEO SELF-TEST. If Code 67 or 79/539 is present, ECA is receiving and recognizing A/C input from pin No. 10. Check for other possible causes of low idle. If Codes 67 and 79/539 are not present, go to step 43).

43) Check A/C Input Circuit Turn ignition off. Install breakout box, leaving ECA disconnected. Set DVOM to 20-volt scale. Turn A/C on. Turn ignition on. Measure voltage between test pins No. 10 and 40. If voltage is 10.5 volts or more, replace ECA and repeat QUICK TEST. If voltage is less than 10.5 volts, repair open A/C circuit. Remove breakout box, reconnect all components and repeat QUICK TEST.

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

1. Technician did not perform brief Wide Open Throttle (WOT) after Dynamic Response Code.
2. Faulty mechanical engine components.
3. Engine did not go over 2000 RPM during WOT.

This test is only intended to diagnose

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

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

1) Code 77/538 Displayed: System Failed To Recognize WOT Test Repeat KOER SELF-TEST as follows

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

Ensure vehicle speed reached 2000 RPM during WOT. If Code 77/538 is present, replace ECA. If Code 77/538 is not present, vehicle has passed dynamic response test. Service other codes if necessary.

Perform this test only when instructed by QUICK TEST or if directed by CIRCUIT TEST QA. This circuit test does not apply to vehicles with electronic instrument cluster. To prevent replacing good components, be aware that fuse, bulb or bulb socket may be cause of problem. This test is only intended to diagnose

1. STO/MIL circuit.
2. ECA.

Identifying Data Communication Link (DCL) Circuit. Scheme 118

CIRCUIT TEST ML TEST PIN WIRE COLOR ID

1) Malfunction Indicator Light (MIL) Always On If vehicle will not start, go to appropriate circuit test

1. For TFI, CIRCUIT TEST AA.
2. For DIS, CIRCUIT TEST AB.
3. For EDIS, CIRCUIT TEST AC.

Service all KOEO and Continuous Memory Codes before proceeding with this test. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pins No. 17 and 40 at breakout box. If resistance is more than 5 ohms, replace ECA and repeat QUICK TEST. If resistance is 5 ohms or less, repair short between test pin No. 17 and self-test connector or between test pin No. 17 and MIL light. Reconnect all components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 4). No test procedures have been omitted.

4) Malfunction Indicator Light (MIL) Does Not Light If vehicle will not start, go to step 1). Turn ignition on. Measure voltage between negative battery terminal to ground side of MIL fuse. If voltage is more than 10.5 volts, go to step 6). If voltage is 10.5 volts or less, go to step 5).

5) Check For Voltage At Fuse Turn ignition on. Measure voltage from negative battery terminal to power side of MIL fuse. If voltage is more than 10.5 volts, replace fuse. Verify repair by turning ignition switch to RUN position. If voltage is 10.5 volts or less, repair open MIL/VBAT circuit. Verify repair by turning ignition switch to RUN position.

6) Check Voltage At VBAT Circuit Turn ignition on. Measure voltage between VBAT side of MIL bulb and negative battery terminal. If voltage is 10.5 volts or less, repair open in MIL circuit between fuse and bulb. Verify repair by turning ignition switch to RUN position. If voltage is more than 10.5 volts, go to step 7).

7) Check MIL Bulb Response To Grounding Turn ignition off. Attach jumper wire between ground side of MIL bulb socket and chassis ground. Turn ignition on. If MIL light comes on, turn ignition off. Remove jumper wire, and go to step 8). If MIL light does not come on, turn ignition off and remove jumper wire. Replace MIL bulb socket. Turn ignition on to verify correct MIL operation.

8) Check Continuity Of MIL Circuit Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 17 at breakout box and MIL terminal at wiring harness connector. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or more, repair open MIL circuit. Turn ignition on to verify correct MIL operation.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 8) to step 10). No test procedures have been omitted.

10) MIL On Intermittently, Check For Intermittent Short From STO To Ground If vehicle does not start, go to step 1). Light comes on when a fault code is present. Service all fault codes before proceeding. If no codes are output, proceed with this test. Enter KOEO wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Check DVOM for indication of fault while performing wiggle test on harness in following areas

1. From self-test connector to dash panel.
2. Dash panel to ECA.
3. Dash panel to Malfunction Indicator Light (MIL).

If a fault is indicated, repair as necessary and repeat QUICK TEST. If a fault is not indicated, fault cannot be duplicated at this time. Testing is complete.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 10) to step 15). No test procedures have been omitted.

15) MIL Flashes With Erratic Idle Symptoms indicate STI is grounded and ECA is performing self-test without tester installed. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between STI connector and engine block ground. If resistance is 10,000 ohms or less, repair short circuit. Reconnect ECA, and turn ignition on to verify correct MIL operation. If resistance is more than 10,000 ohms, MIL circuit is okay. Verify symptom, and test for other rough idle symptoms.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 20). No test procedures have been omitted.

20) CHECK ENGINE Message Displayed If vehicle will not start, go to step 1). Perform KOEO SELF-TEST. If result is Code 11-10-11 or Code 111-10-111 (pass code), fault is in instrument cluster. If pass code is not displayed, service codes as necessary.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 20) to step 25). No test procedures have been omitted.

25) Continuous Memory Code 529 Or 533: CHECK ENGINE Or CHECK DCL Message Displayed Codes 529 and 533 indicate circuit fault has occurred on Data Communications Link (DCL). These codes can occur alone or with another code. Fault will occur under following conditions

1. Code 529 indicates ECA or Data Communicator Link (DCL) circuit failure.
2. Code 533 indicates Data Communication Link to Electronic Instrument Cluster circuit failure.

If vehicle does not start, go to step 1). If vehicle starts, clear continuous memory codes. Wait 5 minutes, and repeat KOEO SELF-TEST. If result is pass code (Code 11-10-11 or 111-10-111), fault is in instrument cluster. If pass code is not displayed, service codes as necessary.

Perform this test when directed by QUICK TEST. This test is only intended to diagnose EEC-IV portion of ignition system. For additional information on ignition system and component testing, see I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. To prevent replacing good components, be aware following non-EEC related areas may be cause of problem

1. TFI module.
2. Ignition coil.
3. Spark plugs and/or wires.
4. Distributor.
5. Secondary ignition short to ground.

This test is intended to diagnose

1. IDM circuit.
2. ECA assembly.

IDM Circuit Schematic. Scheme 119

CIRCUIT TEST NA TEST PIN WIRE COLOR ID

1) Continuous Memory Code 14/211 Code 14/211 indicates 2 successive erratic Profile Ignition Pick-Up (PIP) pulses occurred, resulting in a possible engine miss or stall. Check for following possible causes of fault

1. Loose wires or connectors.
2. Secondary ignition short to ground.
3. On-board transmitter equipment (2-way radio).

Repair any problems found as necessary. Clear code, and repeat QUICK TEST. If problem is not found, go to step 2) for vehicles with Computer-Controlled Dwell (CCD) or step 3) for all others. For ignition system application, see ENGINE/VIN ID article in the ENGINE PERFORMANCE Section.

2) Code 18/212: Check IDM Circuit Continuity (CCD) Continuous Memory Code 18/212 indicates loss of IDM input to ECA. Possible causes for this fault are

1. Open or shorted circuit in wiring harness.
2. Faulty TFI module.
3. Faulty ECA.

Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect TFI module. Measure resistance between test pin No. 4 at breakout box and IDM terminal at TFI wiring harness connector. If resistance is 5 ohms or less, go to step 4). If any resistance is more than 5 ohms, repair open circuit. Clear codes, and repeat QUICK TEST.

3) Code 18/212: Check IDM Circuit Continuity (Non-CCD) Continuous Memory Code 18/212 indicates loss of IDM input to ECA. Possible causes for this fault are

1. Open or shorted circuit in wiring harness.
2. Faulty TFI module.
3. Faulty ECA.

Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect ignition coil and TFI module. Measure resistance between test pin No. 4 at breakout box and IDM terminal at TFI wiring harness connector. If resistance is not 20,000-24,000 ohms, repair open circuit. Clear codes, and repeat QUICK TEST. If resistance is 20,000-24,000 ohms, go to step 4).

4) Check IDM Circuit For Short To Power (Except VREF) Turn ignition off. Leave TFI module disconnected. Measure voltage between breakout box test pin No. 4 and negative battery terminal. Measure voltage between test pin No. 4 and test pins No. 40 and 60 at breakout box. If voltage is more than 10.5 volts, repair short circuit. Clear codes, and repeat QUICK TEST. If voltage is 10.5 volts or less, go to step 5).

5) Check IDM Circuit For Short To PIP & VREF Turn ignition off. Leave ECA and TFI module disconnected. For shorts to PIP, measure resistance between test pins No. 4 and 56 at breakout box. For shorts to VREF, measure resistance between test pins No. 4 and 26 at breakout box. If either 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 step 6).

6) Check IDM Circuit For Short To Ground Turn ignition off. Disconnect ignition coil on vehicles without CCD. On all models, set DVOM to 200-k/ohm scale. Measure resistance between test pin No. 4 and test pins No. 40, 46 and 60 at breakout box. If each resistance is more than 10,000 ohms, go to step 7). If any resistance is 10,000 ohms or less, repair short to ground in IDM circuit. Clear codes, and repeat QUICK TEST.

7) Check TFI Module Turn ignition off. Connect ECA to breakout box. Connect TFI wiring harness connector. Set DVOM to 20-volt scale. Connect DVOM between test pins No. 4 and 16 at breakout box. Start engine. Observe DVOM for voltage surge while lightly tapping on TFI module to simulate road shock. Wiggle all TFI wiring and harness connectors. If fault (voltage surge) is indicated, disconnect and inspect TFI harness connectors and terminals for damage. If connector and terminals are okay, check ignition system. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If fault (voltage surge) is indicated, go to step 8).

8) Check ECA & Harness Connectors Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. If connector is damaged, repair as necessary. Clear codes, and repeat QUICK TEST. If connector is okay, go to step 9).

9) Check ECA For Short To Power Turn ignition off. Connect ECA to breakout box. Disconnect TFI module. Measure voltage between test pin No. 4 at breakout box and chassis ground. Turn ignition on. Measure voltage between test pin No. 4 and test pins No. 40, 46 and 60 at breakout box. If either voltage reading is more than 10.5 volts, replace ECA and repeat QUICK TEST. If both voltage readings are 10.5 volts or less, go to step 10).

10) Check ECA For Short To Ground Turn ignition off. Connect ECA to breakout box. On models without CCD, disconnect ignition coil. On all models, disconnect TFI module. Measure resistance between test pin No. 4 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check ignition system. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If resistance is 10,000 ohms or less, replace ECA and repeat QUICK TEST.

Perform this test when checking computed timing or if directed by QUICK TEST. This test is intended to diagnose

1. SPOUT wiring harness circuit.
2. Base timing.
3. Faulty ECA.

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

1. Basic engine condition (valves, vacuum leaks, valve timing, etc.).
2. Distributor.
3. TFI module.

TFI Spark Timing Check Circuit. Scheme 120

TEST PIN NO. 36 (SPOUT) WIRE COLOR ID

1) Check For Power To ECA Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pins No. 37 and 40 and between test pins No. 57 and 60 at breakout box. If either voltage reading is less than 10.5 volts, go to CIRCUIT TEST B. If both voltage readings are 10.5 volts or more, go to step 2).

2) Check SPOUT Circuit For Continuity Turn ignition off. Disconnect TFI module. Measure resistance between test pin No. 36 at breakout box and SPOUT terminal at TFI module wiring harness connector. If resistance is more than 5 ohms, repair open circuit. Reconnect all components, and verify ignition timing is correct. If resistance is 5 ohms or less, go to step 3).

3) Check SPOUT Voltage At ECA Turn ignition off. Connect ECA to breakout box. Reconnect TFI module. Ensure timing switch on breakout box is in DIST position. Set DVOM on 20-volt AC scale. Start engine. Measure voltage between test pin No. 36 and negative battery terminal. If voltage is 3-10 volts AC, EEC-IV system is okay. Check ignition system. See IGNITION SYSTEMS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If voltage is not 3-10 volts, replace ECA and repeat QUICK TEST.

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

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

Aftermarket devices, such as 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 state and repeat QUICK TEST.

No Codes/Codes Not Listed Circuits. Scheme 121

CIRCUIT TEST QA TEST PIN WIRE COLOR ID

1) Check VREF Voltage At Self-Test Connector Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between test pin No. 26 at breakout box and SIG RTN terminal at self-test connector. If reading is 4-6 volts, go to step 3). If reading is not 4-6 volts, go to step 2).

2) Check STI Circuit Continuity Turn ignition off. Disconnect ECA from breakout box. Measure resistance between test pin No. 48 at breakout box and SIG RTN terminal at self-test connector. If resistance is less than 5 ohms, go to CIRCUIT TEST C. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

3) Check STI Circuit Continuity Turn ignition off. Disconnect ECA from breakout box. Measure resistance between test pin No. 48 at breakout box and Self-Test Input (STI) terminal at pigtail connector. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to step 4).

4) Check STO Circuit Continuity Turn ignition off. Leave ECA disconnected from breakout box. Measure resistance between test pin No. 17 at breakout box and STO terminal at self-test connector. If resistance is less than 5 ohms, go to step 5). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

5) Check EGO Signal For Short To Power Turn ignition off. Leave ECA disconnected from breakout box. Measure voltage between test pin No. 40 or 60 and HEGO SIGNAL test pin No. 29 or 44 at breakout box. For HEGO circuit schematics (Scheme 105)in CIRCUIT TEST H. If voltage is more than 2 volts, go to step 6). If voltage is 2 volts or less, go to step 7).

6) Isolate Short To Harness Or HEGO Sensor Turn ignition off. Leave ECA disconnected from breakout box. Disconnect right/rear HEGO sensor connector. Turn ignition on. Measure voltage between HEGO SIGNAL test pin No. 29 or 44 and test pin No. 40 or 60 at breakout box. If voltage is 2 volts or more, repair short to power in HEGO SIGNAL circuit. Reconnect all components, and repeat QUICK TEST. If voltage is less than 2 volts, replace right/rear HEGO sensor. Reconnect all components, and repeat QUICK TEST.

7) Check STO Circuit For Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Measure resistance between STO terminal at self-test connector and engine ground. If resistance is more than 5 ohms, go to step 8). If resistance is 5 ohms or less, repair STO or MIL circuit for short to ground and repeat QUICK TEST.

8) Check If Power Relay Is Always On Turn ignition off. Leave ECA disconnected from breakout box. Connect DVOM between test pin No. 37 or 57 and pin No. 40 or 60 at breakout box. Turn ignition on and then off. Wait 10 seconds. If voltage does not change from 10.5 volts (or more) to less than 1.0 volt, go to step 9). If voltage changes from 10.5 volts (or more) to less than 1.0 volt, go to step 10).

9) Check VPWR Circuit For Short To Power Turn ignition off. Leave ECA disconnected from breakout box. Disconnect EEC power relay. Connect DVOM to test pin No. 37 or 57 and test pin No. 40 or 46 at breakout box. If voltage is more than 1.0 volt, repair VPWR circuit short to power. Reconnect ECA, and repeat QUICK TEST. If voltage is 1.0 volt or less, replace EEC-IV power relay. Reconnect ECA, and repeat QUICK TEST.

10) Check Malfunction Indicator Light (MIL) Function If MIL is always on, go to CIRCUIT TEST ML, step 1). If MIL is always off, go to CIRCUIT TEST ML, step 4). If MIL is working normally, replace ECA and repeat QUICK TEST.

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

1. ECA.
2. KAPWR wiring harness circuits.

KAPWR Circuit. Scheme 122

TEST PIN NO. 1 (KAPWR) WIRE COLOR ID

1) Check KAPWR Circuit Voltage Code 15/512 indicates ECA power interruption in Keep-Alive Memory (KAM). Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure voltage between test pin No. 1 and pin No. 40 or 60 at breakout box. Observe voltage reading while wiggling, bending and shaking small sections of EEC-IV wiring harness from ECA to dash. If reading is less than 10.5 volts, repair open circuit and repeat QUICK TEST. If reading is 10.5 volts or more, go to step 2).

Continuous Memory Code 15/512 may be displayed when power between ECA and KAPWR is interrupted. This code may be set when a breakout box is installed or battery is disconnected.

2) Inspect Engine Compartment Wire Routing Ensure EEC-IV wiring is not routed close to ignition components or secondary ignition wires. If necessary, reroute EEC wiring. Clear codes, and wait 5 minutes. Repeat KOEO SELF-TEST. If Continuous Memory Code 15/512 is no longer displayed, Continuous Memory Code 15/512 testing is complete. If Continuous Memory Code 15/512 is still present, replace ECA and repeat QUICK TEST.

Perform this circuit test when directed by other CIRCUIT TESTS. This test is only intended to diagnose

1. ECA.
2. Throttle plate linkage.

1) Check For Codes 23, 53, 63, 121, 122 & 123 Disconnect cruise control servo wiring harness connector. Perform KOEO SELF-TEST. If Code 23, 53, 63, 121, 122 or 123 is present, go to appropriate CIRCUIT TEST. See SERVICE CODE REFERENCE CHARTS. Service code(s) as necessary. If pass code (11/111) is displayed, go to step 2). If no code is displayed, go to CIRCUIT TEST QA.

2) Check Throttle Linkage Check throttle and linkage for sticking and binding. If throttle and linkage are okay, replace Throttle Position Sensor (TPS) and repeat QUICK TEST. If throttle and linkage are binding, repair as necessary and repeat QUICK TEST.

Perform this test only when directed by CIRCUIT TEST AA, CIRCUIT TEST AB or CIRCUIT TEST AC. This test is intended to diagnose

1. ISC by-pass air system.
2. MAP system.
3. EGR system.
4. MAF system.

To prevent replacing good components, be aware 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. Engine mechanical components (cam timing, valves, etc.).

1) ISC-BPA Check Try to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to CIRCUIT TEST KE, step 4). If engine does not run as described, go to step 2).

2) Check For RPM Drop Turn ignition off. Connect a tachometer to engine. Start engine. Disconnect ISC solenoid. If RPM drops or engine stalls, reconnect ISC solenoid and go to step 3). If RPM does not drop, go to step 4).

3) Power To MAP/BP Sensor If vehicle is not equipped with a MAP/BP sensor, go to step 8). Test MAP/BP using Ford Motor Co. MAP/BP tester. Disconnect MAP/BP sensor. Turn ignition off. Connect MAP/BP tester between wiring harness and MAP/BP sensor. (Scheme 123) Connect banana plugs of tester into DVOM. Set DVOM on 20-volt scale. With tester connected, turn ignition on. If Green light is on, go to step 4). If light is not on, repair open in VREF circuit and remove MAP/BP tester. Reconnect components, and retest symptom.

MAP/BP Tester & Circuit. Scheme 123

4) MAP/BP Tester Output Reading Measure several known good MAP/BP sensors to obtain average voltage for location and date of testing. With MAP/BP tester and DVOM connected, turn ignition on. Measure MAP/BP voltage at MAP sensor. If voltage is in within specification for specific altitude, go to step 5). See MAP VOLTAGE OUTPUT . If voltage is not within specification for specific altitude, replace MAP/BP sensor.

MAP VOLTAGE OUTPUT

5) Check Vacuum Lines Check vacuum lines for correct routing.Refer to VECI decal. Check MAP sensor vacuum line for leaks and blockage. If vacuum lines are okay, go to step 6). If vacuum lines are not okay, repair as necessary. Repeat QUICK TEST.

6) Check MAP Sensor Turn ignition off. Disconnect vacuum hose from manifold vacuum source. Install vacuum pump to MAP sensor hose. Apply 18 in. Hg vacuum to MAP sensor. If MAP sensor holds vacuum, release vacuum and remove vacuum pump. Reconnect vacuum hose to MAP sensor, and go to step 7). If MAP sensor does not hold vacuum, replace MAP sensor or hose and repeat QUICK TEST.

7) Check Vacuum Manifold Source Turn ignition off. Disconnect MAP sensor vacuum hose from manifold vacuum source. Install vacuum gauge at manifold vacuum source. Start engine and observe vacuum gauge. If manifold vacuum is present, remove vacuum gauge. Reconnect MAP sensor vacuum hose, and go to step 8). If vacuum is not present, remove obstruction. Reconnect all components, and repeat QUICK TEST.

8) Check EGR Vacuum If vehicle is not equipped with EGR system, go to CIRCUIT TEST H, step 2). Disconnect and plug vacuum line at EGR valve. Attempt to start engine. If vehicle did not start previously but starts now or if driveability symptoms are eliminated, go to CIRCUIT TEST DN, step 42). If vehicle could not start previously and still does not start or if vehicle driveability fault is still present, go to step 9).

9) Check EGR Valve Inspect EGR valve for leaks. If valve is fully closed, go to CIRCUIT TEST H, step 2). If EGR valve is leaking or is not fully seated, repair or replace valve as necessary.

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

1. Clutch Engage/Interlock Switch.
2. Neutral Drive/Gear Switch.
3. ECA.
4. Wiring harness circuits CES, CIS, NDS, NGS and SIG RTN.

Neutral Drive Input Circuit (A/T). Scheme 124

CIRCUIT TEST TA TEST PIN WIRE COLOR ID

1) Code 67/522, 525, 527, 528 Or 634 System Identification Code67/522, 525, 527 or 528 is a result of voltage being high at either pin No. 10 (A/C input) or 30 (neutral drive) while cranking engine or during KOEO SELF-TEST. Possible causes for these faults are

1. A/C circuit shorted to power.
2. Clutch engage/interlock circuits open.
3. Neutral drive/gear switch open.
4. Faulty ECA.
5. Starter relay disconnected during self-test.

On all A/T models, go to step 8). On M/T models, go to step 2).

2) Check Neutral Gear/Clutch Input Turn ignition off. Turn A/C off (if equipped). Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pins No. 30 and 46 with transmission in Neutral and clutch pedal up. Measure resistance between test pins No. 30 and 46 with transmission in gear and clutch pedal down. If each resistance is less than 5 ohms, go to step 3). If resistance is 5 ohms or more, go to step 5).

3) Check Neutral Gear/Clutch Input Integrity Turn ignition off. Leave ECA disconnected from breakout box. Measure resistance between test pins No. 30 and 46 with transmission in any gear and clutch pedal up. (Scheme 125) If resistance is less than 5 ohms, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If resistance is 5 ohms or more, go to step 4).

Neutral Gear/Clutch Input Circuit. Scheme 125

4) Check For Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Disconnect clutch engage switch. Measure resistance between test pins No. 30 and 46. If resistance is 10,000 ohms or more, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If resistance is less than 10,000 ohms, repair short circuit. Reconnect all components, and repeat QUICK TEST.

5) Check Neutral Gear/Clutch Engage Switch Turn ignition off. Leave ECA disconnected from breakout box. Locate neutral gear switch (on transmission) and clutch engage switch (at clutch pedal linkage). Disconnect wiring harness at both switches, and inspect connectors for pushed-back pins. Measure resistance across neutral gear switch terminals with transmission in Neutral. Measure resistance across clutch engage switch with clutch pedal down. If each resistance is 5 ohms or less, go to step 6). If resistance is more than 5 ohms, replace open switch. Reconnect all components, and repeat QUICK TEST.

6) Check Neutral Gear/Clutch Harness Turn ignition off. Leave ECA disconnected from breakout box. Disconnect neutral gear and clutch switches. Measure resistance between test pin No. 30 and neutral gear switch wiring harness connector. Measure resistance between test pin No. 30 and clutch engage switch harness connector. Measure resistance between test pin No. 46 and neutral gear switch wiring harness connector. Measure resistance between test pin No. 46 and clutch engage switch wiring harness connector. If any resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and repeat QUICK TEST. If each resistance is less than 5 ohms, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others).

On 4.9L, clutch pedal must be down during KOEO SELF-TEST.

7) Check Clutch Engage Switch (4.9L) Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Hold clutch pedal down and measure resistance between test pins No. 30 at breakout box and starter relay. If resistance is less than 5 ohms, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If each resistance is 5 ohms or more, repair open circuit. Reconnect all components, and repeat QUICK TEST.

8) Check Neutral Drive Input Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Ensure A/C is off (if equipped). Ensure transmission is in Neutral or Park. Turn ignition on. Measure voltage between test pin No. 30 and chassis ground. If voltage is less than 1.0 volt, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If voltage is 1.0 volt or more, go to step 9).

9) Check Neutral Drive Switch Resistance Turn ignition off. Leave ECA disconnected from breakout box. Disconnect wiring harness from neutral drive switch. Measure resistance across switch terminals. If resistance is less than 5 ohms, repair open in NDS circuit. Reconnect all components, and repeat QUICK TEST. If resistance is 5 ohms or more, replace neutral drive switch. Reconnect all components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 9) to step 12). No test procedures have been omitted.

12) Check NDS Circuit For Short To Ground Or Closed Neutral Drive Switch Turn ignition off. Leave ECA disconnected from breakout box. Place transmission in Drive. Measure resistance between test pin No. 30 and test pins No. 40 and 60 at breakout box. If resistance is 10,000 ohms or more, NDS circuit is okay. Diagnose other possible causes. If resistance is less than 10,000 ohms, repair closed neutral drive switch or short circuit. Reconnect all components, and repeat QUICK TEST.

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

1. Engine base condition (cam timing, valves, rings, etc.).
2. Brakes.
3. Transmission fluid, friction elements and cooling.
4. Transfer case linkage or internal condition.

This test is only intended to diagnose

1. Harness circuits 4x4 LOW/ OCIL and OCS.
2. Faulty ECA.

4x4 Low & Overdrive Cancel Ckts. (Touch Drive Option). Scheme 126

4x4 Low & Overdrive Cancel Ckts. (W/O Touch Drive Option). Scheme 127

1) Code 47/633, 65/632 Or 97/631 Code 47/633 indicates 4x4 Low selector lever is not in 4x2 or 4x4 HIGH position during KOEO SELF-TEST. Code 65/632 indicates Overdrive Cancel Switch (OCS) is not cycled between engine ID code and WOT check during KOER SELF-TEST. Code 97/631 indicates OCS circuit fault during KOEO SELF-TEST. Possible causes for these faults are

1. Faulty 4x4 Low switch or 4x4 selector lever position.
2. Faulty OCS switch or switch not cycled.
3. OCS bulb burned out.
4. OCS circuit open or grounded.
5. Faulty ECA.

Perform QUICK TEST. If no codes are present, fault is intermittent and cannot be duplicated at this time. If Code 47/633 or 65/632 is present, go to step 2). If Code 97/631 is present, go to step 3).

2) Cycle 4x4 Or Overdrive Cancel Switch Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. To check 4x4 LOW circuit, measure voltage between test pin No. 12 and test pins No. 40 and 60 at breakout box. To check OCS circuit, measure voltage between test pin No. 41 and test pins No. 40 and 60 at breakout box while cycling overdrive cancel switch. If voltage cycles, replace ECA and repeat QUICK TEST. If voltage does not cycle, go to step 3).

3) Check Circuits For Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, measure resistance between test pin No. 12 and test pins No. 40 and 60 at breakout box. To check OCS circuit, measure resistance between test pin No. 41 and pins No. 40 and 60 at breakout box. If resistance is more than 10,000 ohms, go to step 4) (Code 97/631) or step 6) (Code 47/633 or 65/632). If resistance is 10,000 ohms or less, repair short circuit. Repeat QUICK TEST. If code is still present, go to step 5).

4) Check Power Through OCIL Circuit Turn ignition off. Leave ECA disconnected from breakout box. Measure voltage between test pin No. 32 and test pins No. 40 and 60 at breakout box. If voltage is more than 10.5 volts, replace ECA and repeat QUICK TEST. If voltage is 10.5 volts or less, go to step 5).

5) Check Output Driver Voltage Signal Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on test pin No. 12 at breakout box. (Scheme 128) To check OCS circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on test pin No. 32 at breakout box. If either voltage reading is less than 2 volts, check bulb and fuse. If bulb and fuse are okay, repair open circuit and repeat QUICK TEST. If both voltage readings are 2 volts or more, go to step 6).

Identifying KEY POWER Terminal in Fuse Panel. Scheme 128

6) Check Circuit Continuity Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on test pin No. 12 at breakout box. To check OCS circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on power side of OCS wiring harness connector. Connect DVOM positive lead on test pin No. 41 at breakout box and negative lead on power side of OCS wiring harness connector. If either resistance reading is 5 ohms or more, repair open circuit and repeat QUICK TEST. If both resistance readings are less than 5 ohms, go to step 7).

7) Check Circuits For Short To Power Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, measure resistance between test pin No. 12 and test pins No. 37 and 57 at breakout box. To check OCS circuit, measure resistance between test pin No. 32 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 41 and test pins No. 37 and 57 at breakout box. If resistances are more than 10,000 ohms, replace switch and repeat QUICK TEST. If any resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST.

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

1. Engine base condition (cam timing, valves rings, etc.).
2. Brakes.
3. Transmission fluid, friction elements and cooling.

This test is not intended to diagnose transmission. This test is intended to diagnose

1. Wiring harness circuits M/CCC, CCO, CCS, EPC, SS3/4, SS1, SS2, SS3, SIG RTN, EPC PWR and VPWR.
2. Faulty ECA.

CIRCUIT TEST TC ACRONYMS

E4OD Solenoid Circuits. Scheme 129

E4OD SERVICE CODE IDENTIFICATION

TEST PINS NO. 37 & 57 (EPC PWR) WIRE COLOR ID

1) OUTPUT STATE CHECK Code 91/621, 92/622, 93/626, 94/627, 629, 641 or 652 indicates shift solenoid did not respond to ECA command. Possible causes for these faults are

1. Faulty Manual Lever Position (MLP) sensor.
2. Circuit open or grounded.
3. Faulty ECA.

To enter OUTPUT STATE CHECK, use only VOM or DVOM. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at self-test connector. Connect positive lead to positive battery terminal. Install a jumper wire between SIG RTN terminal at self-test connector and STI terminal. (Scheme 121)in CIRCUIT TEST QA. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to step 2). If voltage does not increase, depress throttle to WOT and release. If STO voltage goes high, go to step 2). If STO voltage does not go high, leave test equipment connected and go to CIRCUIT TEST QC, step 2).

2) Check Solenoid Electrical Condition Turn ignition off. Disconnect transmission wiring harness connector. Inspect terminals, and repair if damaged. Connect VOM or DVOM positive test lead to solenoid VPWR connector. Connect negative test lead to appropriate solenoid terminal at transmission wiring harness connector. Cycle solenoid output on and off by depressing and releasing throttle 3-5 times. If voltage output changes 0.5 volt or more, fault is in transmission. If voltage output does not change 0.5 volt or more, go to step 3).

3) Check Continuity Between Solenoid & VPWR Circuits Turn ignition off. Leave transmission wiring harness disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between ECA output signal terminal at ECA wiring harness connector and output signal terminal at transmission wiring harness connector. Measure resistance between breakout box test pins No. 37 and 57 (No. 35 for 7.3L diesel) and VPWR terminal at transmission wiring harness connector. If either resistance is less than 5 ohms, repair open circuit and repeat QUICK TEST. If both resistances are 5 ohms or more, go to step 4).

4) Check Solenoid Circuit For Short To Power Or Ground Turn ignition off. Leave ECA disconnected from breakout box. Leave transmission wiring harness disconnected. Measure resistance between ECA output signal test pin and test pins No. 37 and 57 (No. 35 for 7.3L diesel) at breakout box. Measure resistance between ECA output signal test pin and pins No. 40, 46 and 60 at breakout box. Measure resistance between ECA output signal test pin and chassis ground. If either resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.

10) Check VPWR To Solenoid Code 86/566 or 89/629 indicates shift solenoid did not respond to ECA command. Code 99/624 indicates failure of EPC circuit. Code 98/625 indicates EPC driver failure. Possible causes for these faults are

1. Faulty solenoid.
2. Circuit open or grounded.
3. Faulty ECA.

Turn ignition off. Disconnect transmission wiring harness connector. Turn ignition on. Measure resistance between VPWR and EPC PWR terminal at transmission wiring harness connector and chassis ground. If voltage is less than 10.5 volts, repair open circuit and repeat QUICK TEST. If voltage is 10.5 volts or more, go to step 11).

11) Check Solenoid Resistance Turn ignition off. Leave transmission wiring harness connector disconnected. Measure resistance between VPWR and EPC PWR terminal and suspect component terminal at transmission wiring harness connector. If resistance is not 26-40 ohms (A4LD) or 3-7 ohms (except A4LD), fault is in transmission. If resistance is 26-40 ohms (A4LD) or 3-7 ohms (except A4LD), go to step 12).

12) Check Solenoid Signal & VPWR Circuit Continuity Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between breakout box test pins No. 37 and 57 (No. 35 for 7.3L diesel) and VPWR/EPC PWR terminal at transmission wiring harness connector. On A4LD models, measure resistance between CCO or SS3/4 test pin at breakout box and solenoid terminal at transmission wiring harness connector; on all models except A4LD, measure resistance between test pin No. 32 at breakout box and EPC solenoid terminal at transmission wiring harness connector. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is more than 5 ohms, go to step 13).

13) Check Circuit For Short To Power Or Ground Turn ignition off. Leave ECA disconnected from breakout box. Leave transmission wiring harness connector disconnected. On A4LD models, measure resistance between test pin No. 52 or 53 and pins No. 37 and 57 (No. 35 for 7.3L diesel) at breakout box. Measure resistance between test pin No. 52 or 53 and pins No. 40, 46 and 60 at breakout box. On all models except A4LD, measure resistance between test pin No. 38 and test pins No. 37 and 57 (No. 35 for 7.3L diesel) at breakout box. Measure resistance between test pin No. 38 and test pins No. 40, 46 and 60 at breakout box. If either resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.

20) Check Solenoid Resistance KOEO Code 621 (SS1), 622 (SS2), 641 (SS3) or 643 (CCC) indicates failure in shift solenoid circuit. Possible causes for these faults are

1. Faulty shift solenoid.
2. Circuit open or grounded.
3. Faulty ECA.

Turn ignition off. Disconnect transmission wiring harness connector. Measure resistance between suspect shift solenoid at transmission wiring harness connector and chassis ground. If resistance is 13-17 ohms, go to step 21). If resistance is not 13-17 ohms, go to step 22).

21) Check Shift Solenoid For Short To Power Turn ignition off. Disconnect transmission wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Turn ignition on. Measure voltage between suspect shift solenoid at transmission wiring harness connector and chassis ground. If voltage is more than 0.5 volt, repair short to power and repeat QUICK TEST. If voltage is 0.5 volt or less, go to step 22).

22) Check Shift Solenoid For Short To Ground Turn ignition off. Leave transmission wiring harness connector disconnected. Measure resistance between suspect shift solenoid at transmission wiring harness connector and chassis ground. Measure resistance between suspect shift solenoid and other circuits at transmission wiring harness connector. If either resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to step 23).

23) Check Shift Solenoid Circuit Continuity Turn ignition off. Leave transmission wiring harness connector disconnected. Install EEC-IV Breakout Box (T83L-50-EEC-IV) or 4EAT tester, leaving ECA disconnected. Measure resistance between suspect shift solenoid at breakout box and suspect shift solenoid terminal at transmission wiring harness connector. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to step 24).

24) Check Shift Solenoid For Short To Power In Transmission Turn ignition off. Leave ECA disconnected from breakout box. Reconnect transmission wiring harness connector. Measure voltage between test pin No. 60 and suspect shift solenoid terminal at breakout box. If voltage is 0.5 volt or more, replace or repair solenoid short to power. If voltage is less than 0.5 volt, replace ECA and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 30). No test procedures have been omitted.

30) Continuous Memory Codes 621, 622, 641 & 643 Continuous Memory Code 621 (SS1), 622 (SS2), 641 (SS3) or 643 (CCC) indicates a failure was detected in shift solenoid circuit during last 80 warm-up cycles. Possible causes for these faults are

1. Faulty shift solenoid.
2. Circuit open or grounded.

Turn ignition off. Check shift solenoid circuit between ECA and transmission. Repair or replace as necessary. If circuits are okay, go to step 31).

31) Check For Intermittent Short Or Open Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Connect test light between test pin No. 37 and suspect shift solenoid terminal at breakout box. Test light should be at partial brightness. Observe test light while wiggling and bending shift solenoid circuit between transmission and ECA. An open or short to power will be indicated by light going off. A short to ground will be indicated by light getting bright. Repeat procedure for all solenoids. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to step 32).

SHIFT SOLENOID TEST CIRCUITS ID

32) Check For Intermittent Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Disconnect transmission wiring harness connector. Turn ignition on. Connect test light between test pin No. 37 (No. 35 for 7.3L diesel) and suspect shift solenoid terminal at breakout box. Test light should be off. Observe test light while wiggling and bending shift solenoid circuit between transmission and ECA. A short to ground will be indicated by light turning on. Repeat procedure for all solenoids. If fault is indicated, isolate and repair as necessary. If no fault is indicated, problem is intermittent and cannot be duplicated at this time.

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

1. Engine base condition (cam timing, valves rings, etc.).
2. Electrical (alternator, battery, add-on devices, etc.).
3. Transmission shift linkage.

This test is not intended to diagnose transmission. This test is intended to diagnose

1. Wiring harness circuits MLP, TSR, TSL, TSD, TSOD and SIG RTN.
2. ECA.

Manual Lever Position (MLP) Sensor Circuit. Scheme 130

CIRCUIT TEST TD TEST PIN WIRE COLOR ID

1) KOEO Codes 67/634, 522 & 654 KOEO Codes 67/634 522 and 654 indicate MLP sensor is out of self-test range (3770-4607 ohms) when gear selector is in PARK position. Possible causes for these faults are

1. Linkage not adjusted correctly.
2. Faulty Manual Lever Position (MLP) sensor.
3. Circuit open or grounded.
4. Faulty ECA.

Turn ignition off. Apply parking brake. Place transmission gear selector in NEUTRAL position. Place Manual Lever Position Sensor Gauge (T89T-70010-J) in sensor slot. If gauge does not fit, loosen MLP mounting bolts and adjust sensor as necessary. If gauge fits, go to step 2).

2) Check MLP Sensor Circuit Continuity Turn ignition off. Disconnect MLP sensor wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between MLP terminal at MLP sensor wiring harness connector and test pin No. 30 at breakout box. Measure resistance between SIG RTN terminal at MLP sensor wiring harness connector and test pin No. 46 at breakout box. If either resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST. If both resistances are 5 ohms or less, go to step 3).

3) Check MLP Sensor For Short To Power & Ground Turn ignition off. Leave ECA and MLP sensor disconnected. Measure resistance between test pin No. 30 and test pins No. 40, 46 and 60 at breakout box. Measure resistance between test pin No. 30 and chassis ground. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If resistance is 10,000 ohms or more, go to step 4).

4) Check MLP Sensor Resistance Turn ignition off. Connect MLP sensor. Leave ECA disconnected from breakout box. Measure resistance between test pins No. 30 and 46 at breakout box while cycling gear selector. See MLP SENSOR RESISTANCE . If resistance is within specification, replace ECA and repeat QUICK TEST. If resistance is not within specification, replace MLP sensor and repeat QUICK TEST.

MLP SENSOR RESISTANCE

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 7). No test procedures have been omitted.

7) Incorrect Shift/No Shift Turn ignition off. Check transmission fluid. Add or replace if necessary. Test drive vehicle to determine transmission shift patterns. If transmission always remains in 3rd gear when vehicle is operated with shift lever in Drive or Overdrive position, go to next step. If transmission does not operate as described, go to step 9).

8) Visual Inspection Visually check select switch and solenoid wiring harness between ECA and transmission. Repair or replace wiring harness if necessary and repeat QUICK TEST. If wiring harness is okay, go to step 9).

9) Diagnose Transmission Shift Patterns If transmission upshifts and downshifts correctly, EEC-IV system is okay. Fault is in transmission. If transmission does not shift correctly, turn ignition off. Inspect transmission switches and harness connectors for corrosion and damaged pins. Inspect wiring harness for incorrect routing. If any faults are found, repair or replace as necessary. If no faults are found, problem is intermittent and cannot be found at this time.

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

1. Transmission fluid level.
2. Transmission fluid temperature.
3. Ambient temperature.

This test is intended to diagnose

1. TOT sensor.
2. Wiring harness circuits TOT and SIG RTN.
3. Faulty ECA.

Transmission Oil Temp (TOT) Sensor Ckt. Scheme 131

TOT SENSOR (AXOD-E) SPECIFICATIONS

1) KOEO Code 26/636 KOEO Code 26/636 indicate TOT sensor is out of self-test range. Possible causes for these faults are

1. Transmission fluid incorrect temperature.
2. Incorrect sensor resistance.
3. Faulty ECA.

Ensure transmission fluid temperature is more than 50°F (10°C). Repeat QUICK TEST. If Code 26/636 is present, go to step 2). If Code 26/636 is not present, test is complete.

2) Check VREF At Throttle Position Sensor (TPS) Turn ignition off. Disconnect TPS sensor wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. If voltage is 4-6 volts, go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check TOT Sensor Resistance Turn ignition off. Disconnect ECA from breakout box. Allow transmission to cool. Turn ignition on. Measure and record voltage between test pin No. 46 and TOT test pin at breakout box. Start engine, and warm transmission to normal operating temperature. Disconnect ECA from breakout box. Measure voltage between test pin No. 46 and TOT test pin at breakout box. If voltage is within specification, replace ECA and repeat QUICK TEST. If voltage is not within specification, replace TOT sensor and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 10). No test procedures have been omitted.

10) KOEO Code 56 Or 637 KOEO Code 56 and 637 indicate TOT sensor output exceeds self-test maximum voltage. Possible causes for these faults are

1. Transmission fluid temperature incorrect.
2. Open wiring harness circuit.
3. Faulty ECA.

Turn ignition off. Disconnect TOT wiring harness connector. Inspect terminals, and repair if damaged. Connect jumper wire between TOT and SIG RTN terminals. Perform KOER SELF-TEST. If Code 66/638 is present, replace TOT sensor and repeat QUICK TEST. If Code 66/638 is not present, go to step 11).

11) Check TOT & SIG RTN Circuit Continuity Turn ignition off. Leave TOT sensor disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box(T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between TOT circuit at TOT wiring harness connector and TOT test pin at breakout box. Measure resistance between SIG RTN circuit at TOT wiring harness connector and TOT test pin at breakout box. If either resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST. If each resistance is 5 ohms or less, go to step 12).

12) Check TOT Sensor For Short To VPWR Turn ignition off. Leave ECA and TOT sensor disconnected. Measure resistance between TOT test pin and test pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, replace ECA and repeat QUICK TEST. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.

20) KOEO Code 66 Or 638 KOEO Code 66 and 638 indicate TOT sensor output is lower than self-test minimum voltage. Possible causes for these faults are

1. Damaged TOT sensor.
2. Shorted wiring harness circuit.
3. Faulty ECA.

Turn ignition off. Disconnect transmission wiring harness connector. Inspect terminals, and repair if damaged. Perform KOEO SELF-TEST. If Code 56 or 637 is present, replace TOT sensor and repeat QUICK TEST. If Code 66/638 is not present, go to step 21).

21) Check VREF At Throttle Position Sensor (TPS) Turn ignition off. Disconnect TPS sensor wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. see scheme 57 If voltage is 4-6 volts, go to step 22). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

22) Check TOT Sensor Resistance Turn ignition off. Disconnect ECA from breakout box. Measure resistance between TOT test pin at breakout box and test pins No. 40, 46 and 60. If resistance is more than 10,000 ohms, replace ECA and repeat QUICK TEST. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 25). No test procedures have been omitted.

25) Check Transmission Wiring Harness Turn ignition off. Check transmission internal and external wiring and connectors for damage and corrosion. Repair or replace if necessary. If wiring is okay, replace TOT sensor and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 25) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 637/638 Continuous Memory Code 637/638 indicates that a fault has been detected in TOT circuit at one or more times during previous 80 warm-up cycles. Possible causes for these faults are

1. Intermittent fault in TOT sensor.
2. Intermittent short or open in wiring harness.

Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Connect DVOM between test pins No. 2 and 46 at breakout box. Turn ignition on. Shake and bend TOT and SIG RTN wires between transmission and ECA. Voltage should remain stable or change gradually. If voltage drops or surges abruptly, fault in circuit is indicated. If fault is indicated, isolate and repair as necessary. If no faults are found, problem cannot be located at this time.

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

1. Wiring harness circuits CLS, SS1, SS3, EPC, MCCC, TOT, MLP and VPWR.
2. ECA.

E4OD Electronic Transmission Circuit. Scheme 132

TEST PINS NO. 37 & 57 (EPC PWR) WIRE COLOR ID

Note. Procedure begins with step 90). No test procedures have been omitted.

90) Vehicle Preparation Ensure all components are properly connected. Ensure transmission fluid is correct level. Warm engine to normal operating temperature. Perform KOEO and CONTINUOUS MEMORY CODE SELF-TEST. If Code 49/617, 56/637, 59/618, 66/638, 69/619, 62/628, 645, 646, 647, 648 or 656 is present, go to step 93). If none of these codes are present, go to step 91).

91) Drive Cycle Test (E4OD) With transmission gear selector in DRIVE position, press Overdrive Cancel Switch (LED should light). Moderately accelerate vehicle to 40 MPH for at least 15 seconds (30 seconds above 4000' elevation). Transmission should be in 3rd gear. While holding speed steady, press Overdrive Cancel Switch (LED should go off) and accelerate from 40 MPH to 50 MPH. Transmission should shift from 3rd gear to 4th gear. Hold speed steady for 15 seconds. While holding speed steady, lightly apply and release brakes to turn brakelights on. Maintain 50 MPH for about 5 seconds. Stop and park vehicle for a minimum of 20 seconds with transmission gear selector in DRIVE position. Repeat procedure 5 times.

After completing DRIVE CYCLE TEST, perform KOEO and CONTINUOUS MEMORY CODE SELF-TEST. If Code 99/624, 67/634 or 651 is present, go to step 92). If none of these codes are present but Code 29/452 is present, go to CIRCUIT TEST DS. If Code 11/111 (pass code) is present, fault cannot be duplicated at this time.

92) Code 99/624, 67/634 Or 651 Code 99/624 and 651 indicate Electronic Pressure Control (EPC) failure. Code 67/634 indicates that Manual Lever Position (MLP) sensor is out of calibration. Possible causes for these faults are

1. Faulty EPC solenoid.
2. Faulty MLP sensor.
3. Circuit open or grounded.
4. Damaged ECA connector pins.

Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. To test EPC solenoid, connect DVOM to EPC test pin and EPC VPWR test pin at breakout box. To test MLP sensor, connect DVOM to MLP test pin and test pin No. 46 at breakout box. For EPC solenoid and MLP sensor, turn ignition on. Voltage for EPC should be less than 10 volts. Voltage for MLP should be less than 5 volts. Shake and bend EPC/MLP wiring harness. Lightly tap on components to simulate road shock. Voltage should remain stable. If voltage changes or exceeds specification, fault in circuit is indicated. If fault is indicated, isolate and repair as necessary. Clear continuous memory codes, and repeat QUICK TEST. If no faults are found, problem cannot be located at this time.

93) Check Circuit Harness & Connectors Shake and bend EEC-IV wiring harness. Lightly tap on components to simulate road shock. Perform KOEO Continuous Monitor Mode. See CIRCUIT TEST KOEO CONTINUOUS MEMORY CODES . If fault is indicated, isolate and repair as necessary. Clear continuous memory codes, and repeat QUICK TEST. If no faults are found, problem cannot be located at this time.

CIRCUIT TEST KOEO CONTINUOUS MEMORY CODES

SUMMARY

If no service code or Code 11-1-11 or 111-1-111 (pass code) is present, but driveability problem still exists, proceed to EEC-IV DIAGNOSIS BY SYMPTOM . If driveability problem still cannot be located, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptoms or intermittent diagnostic procedures.

EEC-IV DIAGNOSIS BY SYMPTOM

See also:
• FUEL PRESSURE SPECIFICATIONS
• CYLINDER BALANCE TEST SERVICE CODES