Engine Controls - Tests W/codes - 2.0L A/t: Diagnosis Mazda MX-6 I

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 diagnostic trouble codes. CIRCUIT TESTS check circuits, sensors and actuators.

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

DIAGNOSTIC TROUBLE CODES (DTC)

During QUICK TEST, 3 types of diagnostic trouble codes are retrieved: KOEO, KOER and Continuous Memory codes. See QUICK TEST for self-test procedures. Codes may be cleared from PCM memory after they have been recorded or repaired. See CLEARING CODES.

KOEO & KOER SELF-TEST Codes

PCM outputs codes one digit at a time. Record codes in order received. These codes indicate current faults in system and should be serviced in order of appearance. Use DIAGNOSTIC TROUBLE CODE REFERENCE CHART to identify correct CIRCUIT TEST to perform.

If using VOM, 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. 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 1/2-second sweep (separator) and another 6-second delay. see scheme 1

If using MIL/CHECK ENGINE light, diagnostic trouble codes are displayed as flashes.

Scan tester, if used, will count pulses and display them as a digital code. STAR tester cannot be used to read 3-digit codes. Super Star II or New Generation Star tester can be used to read 3-digit codes. If using Super Star II tester, 3-digit codes will only be displayed in fast code mode. If slow code mode is used, display will be blank.

Diagnostic Aids

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

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. Turn ignition off. Ensure test equipment is properly attached. Turn ignition on (engine off). Record all KOEO and Continuous Memory Codes.

If a Code 111 (pass code) is not retrieved, service KOEO codes. See DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS. If PCM will not output codes, go to CIRCUIT TEST QA. If diagnostic trouble codes are retrieved

1. If MIL/CHECK ENGINE light is on, service diagnostic trouble codes in order retrieved. See DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS.
2. If vehicle has a no-start condition, go to CIRCUIT TEST AA.
3. If vehicle displays a Code 111 (pass code) and does not have any symptoms described in previous steps, go to KOER SELF-TEST.

DO NOT enter this test sequence until a Code 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 Sensor (HO2S). 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 diagnostic trouble codes displayed. Check following items

1. If engine starts and stalls (or stalls during self-test), go to CIRCUIT TEST S.
2. If Code 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.
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 (PSP) switch, turn steering wheel at least 1/2 turn and release within 1-2 seconds after ID code portion of test.
5. If Dynamic Response Code appears, perform a brief Wide Open Throttle (WOT). DO NOT perform WOT unless requested.
6. If a Code 111 (pass code) is retrieved during KOER SELF-TEST, service Continuous Memory Codes retrieved in KOEO SELF-TEST. See DIAGNOSTIC TROUBLE CODE REFERENCE CHART.
7. If KOER codes are present, see DIAGNOSTIC TROUBLE CODE REFERENCE CHART. If system will not output codes, go to CIRCUIT TEST QA.
8. If a Code 111 (pass code) is retrieved during Continuous Memory Code portion of KOEO SELF-TEST and no driveability problem exists, EEC-IV testing is complete. If driveability problems are still present, go to «TESTS W/O CODES»(ref-18338) article in the ENGINE PERFORMANCE section.
9. If a Code 111 (pass code) is retrieved during KOER SELF-TEST and intermittent fault(s) continue, go to CONTINUOUS MONITOR MODE (WIGGLE TEST).

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 Procedure

Connect test equipment. see scheme 2 Turn ignition on. 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 diagnostic trouble code may be stored in memory and indicated at diagnostic tester or scan tester. Retrieve code, and perform appropriate test. See DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS.

KOER Wiggle Test Procedure

Connect test equipment. see scheme 2 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 diagnostic trouble code may be stored in memory and indicated at diagnostic tester or scan tester. Retrieve code, and perform appropriate test. See DIAGNOSTIC TROUBLE CODE REFERENCE CHART.

Cylinder Balance Test

This test helps identify a weak or non-contributing cylinder in engines with sequential PFI fuel systems. PCM 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, PCM 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 DIAGNOSTIC TROUBLE CODES table.

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 complete. Repeat Cylinder Balance Test. Total test time is about 3 minutes.

CYLINDER BALANCE TEST DIAGNOSTIC TROUBLE CODES

DIAGNOSTIC TROUBLE CODE REFERENCE CHART

Note. Record trouble codes found during KOEO, KOER and Continuous Memory tests while performing QUICK TEST. Use DIAGNOSTIC TROUBLE CODE REFERENCE CHART to find appropriate CIRCUIT TEST and follow procedures.

Note. Trouble Codes beginning with a "6" are automatic transmission-related problems. If codes are present, see appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.

DIAGNOSTIC TROUBLE CODE REFERENCE CHART

DIAGNOSTIC TROUBLE CODE DEFINITION CHART

CIRCUIT TEST AA - NO-START DI - DISTRIBUTOR 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 the following EEC-IV ignition systems and circuits

1. Powertrain Control Module (PCM).
2. Spark (PCM-controlled).
3. Wiring harness circuits (PIP, SPOUT, IGN GND and VPWR).

To prevent replacement of good components, be aware the 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. Distributor.
6. Camshaft Position (CMP) sensor.
7. Ignition Control Module (ICM).
8. Ignition coil.

REMOTE MOUNTED ICM MODULE LOCATION

ICM Circuit & Connector Terminal ID (AA1). Scheme 4

TEST PIN NO. 16 (IGN GND) WIRE COLOR IDENTIFICATION

TEST PIN NO. 36 (SPOUT) WIRE COLOR IDENTIFICATION

TEST PIN NO. 56 (PIP) WIRE COLOR IDENTIFICATION

1) Check No Start Condition Try to start engine. If engine does not start, go to next step. If engine starts, no-start condition is intermittent. Check and repair ignition system as necessary. See SYSTEM/COMPONENT TESTS article.

2) Attempt To Crank Engine Try to crank 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 next step.

3) Check VREF Signal At TP Sensor Turn ignition off. Disconnect Throttle Position (TP) sensor. Turn ignition on (engine off). Measure voltage at TP sensor harness connector between VREF and SIG RTN. (Scheme 5) If voltage is 4-6 volts, reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

TP Sensor Harness Connector Terminal ID (AA2). Scheme 5

4) 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 14). If spark does not exist, connect spark plug wire and go to step 25).

5) Check For Spark At Coil Remove coil secondary 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 next step.

6) Check Ignition Circuit Ground Continuity Turn ignition off. Disconnect and inspect PCM 60-pin connector. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect ICM and Camshaft Position (CMP) sensor connectors. Measure resistance between test pin No. 16 at breakout box and IGN GND circuit of CMP sensor connector or ICM connector. If resistance is 5 ohms or more, repair open in IGN GND circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

7) Isolate SPOUT Circuit Fault Connect CMP and/or ICM connector. Connect PCM to breakout box. Set breakout box timing switch to DIST position. Try to start vehicle.If vehicle starts, go to step 12). If vehicle does not start, go to next step.

8) Check SPOUT Signal Turn ignition off. Set 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 IGNITION SYSTEM in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. If voltage is not 3-6 volts, go to next step.

9) Check SPOUT & PIP Circuits For Short To Power Turn ignition off. With breakout box installed, move timing switch to COMPUTED position. Disconnect PCM. Disconnect ICM connector. Turn ignition on. Measure voltage between test pin No. 36 (SPOUT) and negative battery terminal. Also, measure voltage between test pin No. 56 (PIP) and negative battery terminal. If either reading is more than 10.5 volts, repair short to power. Remove breakout box, reconnect components and repeat QUICK TEST. If both readings are 10.5 volts or less, go to next step.

10) Check SPOUT & PIP Circuits For Short To Ground Turn ignition off. Measure resistance between test pin No. 36 (SPOUT) and test pins No. 16, 20, 40, 46 and 60 for short to ground. Also, measure resistance between test pin No. 36 and test pin No. 56 for short to PIP. Also, 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 next step. If any reading is less than 10,000 ohms, repair short in wiring harness. Remove breakout box, reconnect components and repeat QUICK TEST. If engine still does not start, go to next step.

11) Isolate Shorts In PCM Turn ignition off. With breakout box installed, reconnect PCM. Disconnect ICM connector. 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 PCM. Remove breakout box, reconnect components and repeat QUICK TEST. If all readings are 500 ohms or more, reconnect components, and go to next step.

12) Check PIP Signal Turn ignition off. With breakout box installed and PCM connected, 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 PCM. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is not 3-7 volts, go to next step.

13) Check Continuity Of PIP Circuit Turn ignition off. Disconnect PCM from breakout box. On models with distributor mounted ICM, disconnect ICM connector. On all other vehicles, disconnect CMP and/or ICM connector. Measure resistance between test pin No. 56 and PIP circuit of ICM or CMP sensor. If resistance is 5 ohms or more, repair open PIP circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 5 ohms, remove breakout box and diagnose ignition system. See IGNITION SYSTEM in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

14) Verify SPOUT Signal If spark was present in step 4), turn ignition off. Disconnect PCM 60-pin connector, and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM connected. 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 21). If voltage is not 3-6 volts, return to step 9).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 21). No test procedures have been omitted.

21) Fuel Pump Check Connect pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning ignition on for one second, and observe pressure gauge. Turn ignition off, and wait 10 seconds. Repeat sequence 5 times. If pressure increases, go to CIRCUIT TEST S. If pressure does not increase, repair fuel system as necessary. See FUEL SYSTEM in BASIC TESTING article in the ENGINE PERFORMANCE section.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 25). No test procedures have been omitted.

25) VPWR Circuit Check Turn ignition off. Disconnect CMP sensor. Turn ignition on. Measure voltage between VPWR circuit of CMP sensor connector and negative battery terminal. If voltage is more than 10.5 volts, go to step 5). If voltage is 10.5 volts or less, go to next step.

26) VPWR Continuity Check Turn ignition off. Disconnect PCM 60-pin connector, and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. Measure resistance between VPWR circuit of CMP sensor connector and test pin No. 37 or 57 at breakout box. If resistance is less than 5 ohms, go to CIRCUIT TEST B. If resistance is 5 ohms or more, repair open in VPWR circuit.

Enter this CIRCUIT TEST only when directed by CIRCUIT TEST C, CIRCUIT TEST J or CIRCUIT TEST PA.

This test is only intended to diagnose

1. Power Control Module (PCM).
2. EEC power relay.
3. Ignition switch.
4. Wiring harness circuits (SIG RTN, PWR GND, VPWR, KAPWR and VREF).

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

1. Battery cables and ground straps.
2. Voltage regulator.
3. Alternator.
4. Ignition switch.

Power Relay Circuit (B1). Scheme 6

TEST PIN NO. 1 (KAPWR) WIRE COLOR IDENTIFICATION

TEST PIN NO. 17 (STO) WIRE COLOR IDENTIFICATION

TEST PIN NO. 37/57 (VPWR) WIRE COLOR IDENTIFICATION

TEST PIN NO. 46 (SIG RTN) WIRE COLOR IDENTIFICATION

TEST PIN NO. 48 (STI) WIRE COLOR IDENTIFICATION

TEST PIN NO. 40/60 (PWR GND) WIRE COLOR IDENTIFICATION

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 next step.

2) Check Continuity Of PWR GND Circuit Turn ignition off. Disconnect PCM, and inspect connector pins. If PCM connector pins are damaged, loose or corroded, repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Measure resistance between test pins No. 40 and 60 at breakout box and negative battery terminal. If one or both readings are 5 ohms or more, repair open in PWR GND circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.

3) Check For Open Between SIG RTN & PWR GND Circuits At PCM Ensure ignition is turned off. With breakout box installed and PCM 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 one or both readings are 5 ohms or more, replace PCM. Remove breakout box, and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.

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 of Data Link Connector (DLC). If resistance is 5 ohms or more, repair open in SIG RTN circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.

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 positive battery terminal for open circuit. If voltage is 10.5 volts or more, go to next step.

Note. Vehicles equipped with Power Distribution Boxes use a diode to provide electrical surge protection for the ignition switch and Ignition Control Module (ICM). If a no-start/no-code condition exists, ensure diode continuity in one direction only is present before going to step 6).

6) Check Ignition Circuit Voltage At EEC Power Relay Ensure PCM is connected to breakout box and 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, repair open in ignition switch circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step.

7) Check PWR GND Circuit Continuity Turn ignition off. With PCM 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. If reading is less than 10 ohms, go to next step.

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 PCM. Remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

9) Check VPWR Circuit Voltage Turn ignition off. Install EEC power relay. Turn ignition on. With PCM 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 PCM and EEC power relay. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is less than 10.5 volts, replace EEC power relay. Remove breakout box, reconnect components and repeat QUICK TEST.

Perform this test when a check for VREF signal has failed in sensor input CIRCUIT TESTS AA, DA-DR or 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 PCM. This consistent voltage signal is used on all 3-wire sensors.

This circuit test is only intended to diagnose the following components and circuits

1. Powertrain Control Module (PCM).
2. Vehicle wiring harness circuits (SIG RTN and VREF).

Reference Voltage Circuit & Connector Terminal ID (C1). Scheme 7

TEST PIN NO. 26 (VREF) WIRE COLOR IDENTIFICATION

TEST PIN NO. 46 (SIG RTN) WIRE COLOR IDENTIFICATION

1) Check Battery Power Circuit Turn ignition off. Disconnect PCM 60-pin connector, and inspect it for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Turn ignition on. Measure and record voltage between breakout box test pin No. 37 and SIG RTN terminal of Data Link Connector (DLC). Also, 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). Go to CIRCUIT TEST B. If voltages are 10.5 volts or more and do not differ from one another by more than 1.0 volt, go to next step.

2) Check VREF Voltage With breakout box installed and PCM 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 next step. If voltage is more than 6 volts, go to step 4). If voltage is less than 4 volts, go to step 5).

3) Check VREF & SIG RTN Circuit Continuity Turn ignition off. Disconnect PCM. 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. Also, 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. Remove breakout box, reconnect components and repeat QUICK TEST. If either reading is 5 ohms or more, repair open in VREF or SIG RTN circuit. Remove breakout box, reconnect components and repeat QUICK TEST.

4) Check For Excess VREF Circuit Voltage Turn ignition off. Ensure PCM is disconnected. With breakout box installed, disconnect 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 PCM. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is 0.5 volt or more, repair short to battery power in wiring harness. Remove breakout box, reconnect components and repeat QUICK TEST.

5) Check For Shorted TP Sensor Turn ignition off. Connect PCM to breakout box. Disconnect Throttle Position (TP) sensor connector 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 TP sensor. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is less than 4 volts, go to next step.

6) Check For Shorted EVP Sensor Turn ignition off. Disconnect EVP sensor. Turn ignition on. Measure voltage between test pins No. 26 and 46. If voltage is 4 volts or more, replace EGR Valve Position (EVP) sensor. Remove breakout box, reconnect components and repeat QUICK TEST. If voltage is less than 4 volts, reconnect EVP sensor and go to next step.

7) Check VREF Circuit For Short To Ground Turn ignition off. Disconnect PCM. Disconnect TP sensor and EVP sensor. Measure resistance between test pin No. 26 and test pins No. 20, 40, 46 and 60. If any resistance is less than 1000 ohms, repair short to ground. Remove breakout box, reconnect components and repeat QUICK TEST. If original problem still exists, replace PCM and repeat QUICK TEST. If readings are 1000 ohms or more, replace PCM. Remove breakout box, reconnect components 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 IAT sensor. Engine coolant temperature must be more than 50°F (10°C) to pass KOEO SELF-TEST and more 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 percent due to sensor and VREF variations.

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

1. Intake Air Temperature (IAT) sensor.
2. Engine Coolant Temperature (ECT) sensor.
3. Wiring harness circuits (IAT, ECT and SIG RTN).
4. Powertrain Control Module (PCM).

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

1. Coolant level low.
2. Cooling system, water pump or fan.
3. Engine operating temperature.
4. Engine oil level low.
5. Thermostat.
6. Air cleaner duct.
7. Ambient temperature.

Temperature Sensor Circuit & Connector Terminal ID (DA1). Scheme 8

TEST PIN NO. 7 (ECT) WIRE COLOR IDENTIFICATION

TEST PIN NO. 25 (IAT) WIRE COLOR IDENTIFICATION

TEST PIN NO. 46 (SIG RTN) WIRE COLOR IDENTIFICATION

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

1. Ambient temperature less than 50°F (10°C).
2. Low coolant level.
3. Faulty harness connector.
4. Faulty sensor.

Start engine and run until engine is at normal operating temperature. 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 114 or 116 is present, go to next step. If none of these codes are present, service other codes as necessary.

2) Check VREF Circuit Voltage At TP Sensor Turn ignition off. Disconnect Throttle Position (TP) sensor. With ignition on and engine off, measure voltage at TP sensor wiring harness connector between VREF and SIG RTN. see scheme 8 If voltage is 4-6 volts, reconnect TP sensor and go to next step. 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 terminals. See ACT & ECT SENSOR SPECIFICATIONS table. If resistance is not within specification, replace suspected sensor 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 116 at this time. Go to CIRCUIT TEST AA.
2. For diagnosing vehicles with ECT sensor, without a no-start condition, go to next step.

4) Check Temperature Sensor Resistance Warm engine to normal operating temperature. Turn ignition off. Disconnect suspect sensor. Run engine at 2000 RPM for 2 minutes. Measure resistance between sensor terminals. See ACT & ECT SENSOR SPECIFICATIONS table. If resistance is within specification, replace PCM and repeat QUICK TEST. If sensor is not within specification, replace sensor and repeat QUICK TEST.

ACT & ECT SENSOR SPECIFICATIONS

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 118 Or 113: Induce Opposite Code (Code 112 Or 117) Code 118 (ECT) or 113 (IAT) indicate corresponding sensor signal is more than self-test maximum. Maximum signal voltage for ECT and IAT sensor is 4.6 volts. Possible causes for excess voltage signals are

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

Turn ignition off. Disconnect suspect temperature sensor. Connect a jumper wire between SIG RTN terminal at sensor and SIG RTN terminal at sensor wiring harness connector. Repeat KOEO SELF-TEST. If Code 112 or 117 is displayed, replace suspect sensor, remove jumper wire, and repeat QUICK TEST. If Code 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 PCM 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 7 (ECT sensor) or test pin No. 25 (IAT sensor) at breakout box and SIG RTN 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 PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If either reading is 5 ohms or more, repair open circuit. Remove breakout box, 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 112 or 117: Induce Opposite Code (113 or 118) Code 117 (ECT) or 112 (IAT) indicates sensor signal is less than self-test minimum. Minimum signal for IAT and ECT sensor is 0.2 volt. Possible causes for this fault are

1. Circuit grounded in wiring harness.
2. Faulty sensor.
3. Faulty PCM.
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 113 or 118 is displayed, replace sensor and connect harness. Repeat QUICK TEST. If Codes 113 or 118 is not displayed, go to next step.

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

22) Check Temperature Sensor Signal For Shorts To Ground Turn ignition off. Disconnect suspect sensor. Disconnect PCM 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 7 (ECT) or 25 (IAT) and test pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace PCM. Remove breakout box, reconnect all components, 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 112, 113, 117 Or 118: Check Sensor A Continuous Memory Code 113 or 118 indicates sensor signal is more than self-test maximum of 4.6 volts. Code is set during normal driving conditions. Continuous Memory Code 112 or 117 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 PCM.

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 next step.

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 PCM. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and repeat QUICK TEST. If no fault is found, go to next step.

92) Inspect PCM & Wiring Harness Connectors Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. 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.

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

1. MAF sensor.
2. Wiring harness circuits (VPWR, PWR GND, MAF and MAF RTN).
3. Powertrain Control Module (PCM).

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

1. Air cleaner element.
2. Inlet air duct.
3. Throttle body.

Code 159, retrieved during KOEO SELF-TEST, indicates voltage exceeded .7-volt test range. Code 159, retrieved during KOER SELF-TEST, indicates voltage is not within .2-1.5 volts operating range.

MAF Sensor Circuit & Connector Terminal ID (DC1). Scheme 9

TEST PIN NO. 9 (MAF RTN) WIRE COLOR IDENTIFICATION

TEST PIN NO. 50 (MAF) WIRE COLOR IDENTIFICATION

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

TEST PINS NO. 40 & 60 (PWR GND) WIRE COLOR ID

MAF SIGNAL VOLTAGE (1)

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

1) Code 159: Check VPWR Circuit Voltage Code 159 indicates that MAF sensor was out of range during KOEO or KOER SELF-TEST. Possible causes for this fault are

1. Air leak before or after MAF sensor.
2. Faulty MAF sensor.
3. Faulty IAC solenoid.
4. Open or grounded wiring harness.
5. Faulty PCM.

Repeat QUICK TEST. If Code 412 is present, go to CIRCUIT TEST KE, step 1). If Code 411 is present, go to CIRCUIT TEST KE, step 15). If Code 411 or 412 is not present, go to next step.

2) VPWR Circuit Voltage Check Turn ignition off. Disconnect MAF sensor connector. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between VPWR terminal at MAF sensor wiring harness connector and negative battery terminal. If voltage is less than 10.5 volts, repair open in VPWR circuit and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step.

3) Check MAF Sensor Ground Turn ignition on. With MAF sensor disconnected, measure voltage between VPWR terminal and PWR GND terminal at MAF sensor connector. If voltage is less than 10.5 volts, repair open PWR GND circuit. Connect MAF sensor, and repeat QUICK TEST. If voltage is 10.5 volts or more, go to step 13).

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) Continuous Memory Code 157: Check For Intermittent Sensor Failure Continuous Memory Code 157 indicates MAF signal was less than 0.4 volt sometime during last 80 warm-up cycles. Possible causes for this fault are

1. Open MAF circuit.
2. MAF circuit shorted to ground.
3. Faulty MAF sensor.
4. MAF sensor disconnected.

Clear continuous memory. Start engine and allow to idle for 5-10 minutes. Increase engine speed to 1500 RPM for 5 seconds. Perform KOEO SELF-TEST. If Code 157 is present, go to step 13). If Code 157 is not present, go to next step.

11) Monitor MAF Circuit Under Simulated Road Shock Turn ignition off. Disconnect and inspect 60-pin connector at PCM. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Connect DVOM between MAF test pin and MAF RTN test pin. See appropriate table at beginning of this CIRCUIT TEST. DVOM should read about 0.4 volt. Start engine and allow to idle. Lightly tap on MAF sensor and wiggle wiring harness to simulate road conditions. If sudden change in DVOM reading occurs, fault is indicated. If fault is indicated, replace MAF sensor and repeat QUICK TEST. If no fault is indicated, leave DVOM connected and go to next step.

12) Check Wiring Harness For Open Or Short Circuit Turn ignition on. Shake and bend small sections of wiring harness starting at MAF sensor and working toward dash panel. Shake and bend small sections of wiring harness starting at dash panel and working toward PCM. If fault is indicated, isolate and repair as necessary. If fault is not indicated, problem is intermittent and cannot be duplicated at this time.

13) Codes 129 Or 157: Check For Air Leak At MAF Sensor Check for broken or loose air outlet tube clamps at throttle body and air cleaner assembly. Repair or replace as necessary. If no faults are found, go to next step.

14) Check Continuity Of MAF & VPWR Circuit Turn ignition off. Disconnect MAF sensor and PCM wiring harness connector. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between MAF terminal of MAF sensor wiring harness connector and test pins No. 37 and 57. Measure resistance between MAF terminal of MAF sensor wiring harness connector and test pin No. 50. If resistance is more than 5 ohms, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is 5 ohms or more, go to next step.

15) Check MAF Signal For Short To Ground Turn ignition off. Ensure MAF sensor and PCM wiring harness are disconnected. Measure resistance between test pin No. 50 and test pins No. 9, 40 and 60. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are 10,000 ohms or more, go to next step.

16) Turn ignition off. Ensure MAP sensor and PCM wiring harness connectors are disconnected. Measure resistance between PWR GND terminal at MAF sensor wiring harness connector and negative battery terminal. If resistance is 10 ohms or more, repair open PWR GND circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is less than 10 ohms, go to next next step.

17) Check Continuity Of MAF RTN Circuit Ensure ignition is turned off. Measure resistance between MAF RTN terminal of MAF sensor wiring harness connector and test pin No. 9. If resistance is more than 5 ohms, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is 5 ohms or more, go to next step.

18) Check MAF Circuit For Short To Ground Turn ignition off. Ensure MAF sensor is disconnected. Connect PCM to breakout box. Measure resistance between test pin No. 50 and test pins No. 9, 40 and 60. If any reading is less than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are 10,000 ohms or more, go to next step.

19) Check MAF Circuit Output Turn ignition off. Connect MAF sensor wiring harness connector. Start engine. Measure resistance between test pin No. 50 and negative battery terminal. If voltage is .36-1.50 volts, go to next step. If voltage is not .36-1.50 volts, replace MAF sensor. Remove breakout box, reconnect all components, and repeat QUICK TEST.

20) With engine running, measure resistance between test pin No. 9 and test pin No. 50. If voltage is .36-1.50 volts, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage is not .36-1.50 volts, replace MAF sensor. Remove breakout box, reconnect all components, and repeat QUICK TEST.

Note. Code 158 may be caused by foreign material blocking MAF sensor screen creating an airflow restriction. If contaminates are found on screen, check air filter installation in air cleaner tray, and proper sealing or air cleaner/tube before proceeding.

21) Code 158: Repeat KOEO SELF-TEST Turn ignition off. Disconnect MAF sensor wiring harness connector. Start engine, and allow it to idle for one minute. Turn ignition off. Repeat KOEO SELF-TEST. If Code 157 is present, replace MAF sensor and repeat QUICK TEST. If Code 157 is not present, go to next step.

22) Check MAF Circuit For Short To VPWR Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Measure resistance between MAF and VPWR terminals at MAF sensor wiring harness connector. If resistance is 10,000 ohms or more, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is less than 10,000 ohms, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. Remove breakout box, reconnect all components, and repeat QUICK TEST.

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

1. EGRP sensor.
2. Wiring harness circuits (EGRP, SIG RTN, VREF, EGR Solenoids and VPWR.
3. Powertrain Control Module (PCM).
4. Vacuum lines (EGR Solenoids and EGR.

EGRP Sensor Connector Terminal ID (DD1). Scheme 10

EGR Solenoid Connector Terminal ID (DD2). Scheme 11

1) Code 327: Attempt To Generate Code 337 Code 327 indicates EGR Position (EGRP) sensor signal is less than self-test minimum. Possible causes for this fault are

1. Faulty EGRP sensor/EGR valve assembly.
2. Open sensor VREF or SIG RTN circuits.
3. Open sensor VREF circuit.
4. Short to ground in sensor EGRP circuit.
5. Faulty Powertrain Control Module (PCM).

Turn ignition off. Disconnect EGRP sensor connector. Connect jumper wire between terminals VREF and EGRP of EGRP sensor wiring harness connector. Repeat KOEO and KOER SELF-TEST. If Code 337 is displayed, replace EGRP sensor/EGR valve assembly. Remove jumper wire, and repeat QUICK TEST. Disregard any other codes that are set at this time. If Code 337 is not displayed, remove jumper wire, and go to next step.

2) Check EGRP VREF Voltage Turn ignition on. Ensure EGRP sensor is disconnected. Measure voltage between VREF and SIG RTN terminals at EGRP sensor connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check EGRP Sensor SIG RTN Circuit Continuity Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between SIG RTN terminal of EGRP sensor connector and test pin No. 46 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

4) Check For Short To Ground In EGRP SIG RTN Circuit Measure resistance between test pin No. 27 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If any reading is 10,000 ohms or less, repair short to ground. Remove breakout box, reconnect all components, 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 337: Attempt To Generate Code 327 Code 337 indicates EGR Position (EGRP) sensor signal is more than self-test minimum. Possible causes for this fault are

1. Open or short in EGRP circuit.
2. Faulty EGRP sensor/EGR valve assembly.
3. Faulty EGR Vacuum (EGRV) solenoid valve.
4. Faulty Powertrain Control Module (PCM).
5. Improper EGR valve vacuum hose routing.

Turn ignition off. Disconnect EGRP sensor connector. Connect jumper wire between EGRP and SIG RTN terminals of EGRP sensor wiring harness connector. Repeat KOEO and KOER SELF-TEST. If Code 327 is displayed, remove jumper wire, and go to step 13). Disregard any other codes that are set at this time. If Code 327 is not displayed, remove jumper wire, and go to next step.

11) Check EGRP Circuit Continuity Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair connector as necessary. Ensure EGRP sensor is disconnected. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between EGRP terminal at EGRP sensor connector and test pin No. 27 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

12) Check For Short To Power In EGRP Circuit Measure resistance between test pin No. 27 and test pins No. 26, 37 and 57 at breakout box. If all readings are more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

13) Check Vacuum At EGRV Solenoid Valve Turn ignition off. Disconnect EGRV solenoid vacuum line at EGRV solenoid output port. Install vacuum gauge at output port of EGRV solenoid. Start engine and allow it to idle. Observe vacuum gauge. If vacuum is present, replace EGRV solenoid. Remove vacuum gauge. Reconnect all components and repeat QUICK TEST. If vacuum is not present, check EGR valve vacuum hose routing. Repair as necessary. If hose routing is okay, replace EGRP sensor/EGR valve assembly. Remove vacuum gauge. Reconnect all components 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 571 & 572: Check EGR Vent & Vacuum Solenoids Resistance Code 571 indicates failure in EGR vent solenoid circuit. Code 572 indicates failure in EGR vacuum solenoid circuit. Possible causes for this fault are

1. Open or short in wiring harness.
2. Faulty EGR vent & vacuum solenoid.
3. Faulty Powertrain Control Module (PCM).

Turn ignition off. Disconnect EGR Vent (Code 571) or EGR Vacuum (Code 572) solenoid connector. Measure resistance between solenoid connector terminals. If resistance is 30-70 ohms, go to next step. If resistance is not 30-70 ohms, replace solenoid, and repeat QUICK TEST.

21) Check Solenoid VPWR Circuit Turn ignition on. Ensure solenoid to be tested is disconnected. Measure voltage between negative battery terminal and VPWR terminal at solenoid connector. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open circuit. Repeat QUICK TEST.

22) Check Solenoid Circuit Continuity Turn ignition off. Ensure solenoid to be tested is disconnected. Disconnect PCM 60-pin connector. Inspect for damage, and repair if necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. If testing EGR vent solenoid, measure resistance between test pin No. 12 at breakout box and EGR vent solenoid terminal at solenoid connector. If testing EGR vacuum solenoid, measure resistance between test pin No. 33 at breakout box and EGR vacuum terminal at solenoid connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

23) Check For Solenoid Circuit Short If testing EGR vent solenoid, measure resistance between test pin No. 12 and test pins No. 37, 40, 57 and 60 at breakout box. If testing EGR vacuum solenoid, measure resistance between test pin No. 33 and test pins No. 37, 40, 57 and 60 at breakout box. If all readings are more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 23) to step 30). No test procedures have been omitted.

30) Code 332: Check Vacuum To EGR Valve Code 332 indicates EGRP sensor input did not change after PCM commanded EGR valve to open. Possible causes for this fault are

1. Faulty vacuum lines.
2. Faulty EGRP/sensor/EGR valve assembly.
3. Faulty EGR vent solenoid.
4. Faulty EGR vacuum solenoid.

Turn ignition off. Disconnect EGR vacuum hose at EGR valve, and connect vacuum gauge to disconnected vacuum hose. Repeat KOEO SELF-TEST, while observing vacuum gauge. If vacuum is less than 1.0 in. Hg throughout KOEO SELF-TEST, go to next step. If vacuum is 1.0 in. Hg or more throughout KOEO SELF-TEST, replace EGRP sensor/EGR valve. Reconnect all components and repeat QUICK TEST.

31) Check EGR Vacuum Hose Ensure EGR valve vacuum hose is disconnected. Insect vacuum hose between EGR valve and both EGR solenoids. Replace hose as necessary. Repeat QUICK TEST. If vacuum hose is okay, reconnect vacuum hose, and go to next step.

32) Check Vacuum To EGR Vacuum Solenoid Turn ignition off. Disconnect vacuum hose from EGR vacuum solenoid input port. Install vacuum gauge to disconnected hose. Start engine and allow it to idle. If vacuum is more than 10 in. Hg, remove vacuum gauge. Reconnect vacuum hose, and go to next step. If vacuum is 10 in. Hg or less, check vacuum hose to EGR vacuum solenoid. Replace hose as necessary. If vacuum hose is okay, check vacuum source for solenoid. Repair as necessary. Repeat QUICK TEST.

33) Check EGR Vacuum Solenoid Valve Turn ignition off. Disconnect vacuum hose from EGR vacuum solenoid output port. Install vacuum gauge to output port of EGR vacuum solenoid. Repeat KOEO SELF-TEST and observe vacuum gauge. If vacuum signal decreases then increases, remove vacuum gauge, and go to next step. If vacuum signal does not decrease then increase, replace EGR vacuum solenoid. Remove vacuum gauge. Reconnect all components and repeat QUICK TEST.

34) Check EGR Vacuum Solenoid Output Port Vacuum Hose Disconnect vacuum hose from EGR vacuum solenoid output port. Inspect vacuum hose for obstructions, cracks and kinks. Replace vacuum hose as necessary, and repeat QUICK TEST. If vacuum hose is okay, reconnect vacuum hose and go to next step.

35) Check EGR Vent Solenoid Vacuum Hose Disconnect EGR vent vacuum hose. Inspect vacuum hose for obstructions, cracks and kinks. Replace vacuum hose as necessary, and repeat QUICK TEST. If vacuum hose is okay, replace EGR vent solenoid. Reconnect vacuum hose, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 35) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 327 Or 337: Check for Intermittent Continuous Memory Code 327 indicates EGRP sensor input to PCM was below minimum acceptable voltage sometime during vehicle operation. Continuous Memory Code 337 indicates EGRP sensor input to PCM was more than the maximum acceptable voltage sometime during vehicle operation. Possible causes for this fault are

1. Faulty EGRP/sensor/EGR valve assembly.
2. Intermittent open in EGRP sensor SIG RTN circuit.
3. Intermittent open in EGRP circuit.
4. Intermittent open in EGRP sensor VREF circuit.
5. Intermittent short to power in EGRP circuit.

Enter CONTINUOUS MONITOR MODE (WIGGLE TEST). Observe test equipment and perform the following

1. Lightly tap on EGRP sensor (to simulate road shock).
2. Wiggle sensor wiring harness connector.

If a fault is indicated, inspect EGRP sensor connector and terminals. Repair as necessary. If connector and terminals are okay, replace EGRP sensor/EGR valve assembly. Clear codes, and repeat QUICK TEST. If a fault is not indicated, go to next step.

91) Check For Intermittent Harness Damage: Check For Intermittent Sensor Damage While still in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe test equipment and perform the following. Shake and bend small sections of wiring harness starting at EGRP sensor and working toward dash panel. Also, shake and bend small sections of wiring harness starting at dash panel and working toward PCM. If a fault is indicated, isolate fault and repair as necessary. Clear codes and repeat QUICK TEST. If a fault is not indicated, go to next step.

92) Check PCM Connector Turn ignition off. Disconnect PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Clear codes and repeat QUICK TEST. If connector and wiring are okay, 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 92) to step 100). No test procedures have been omitted.

100) Continuous Memory Code 332: Check EGR Valve Function Continuous Memory Code 332 indicates EGR valve did not open when engine load and requested conditions had been met sometime during vehicle operation. Possible causes for this fault are

1. Faulty EGRP/sensor/EGR valve assembly.
2. Faulty EGR valve vacuum hose.
3. Faulty EGR vacuum or EGR vent solenoid vacuum lines.

Turn ignition off. Disconnect and plug EGR valve vacuum line at EGR valve. Connect vacuum pump to EGR valve. Apply 10 in. Hg to EGR valve. Observe EGR valve and release vacuum. If EGR valve functions properly, remove vacuum pump. Unplug vacuum hose, and go to next step. If EGR valve does not function properly, remove EGRP sensor/EGR valve assembly. Inspect EGR valve for blockage, binding, contamination and leakage. Repair or replace EGR valve assembly as necessary. Clear codes and repeat QUICK TEST.

101) Check EGR Valve Vacuum Hose Disconnect EGR vacuum hose at vacuum source and EGR valve. Inspect vacuum hose for obstructions, cracks and kinks. Replace vacuum hose as necessary. Clear codes and repeat QUICK TEST. If vacuum hose is okay, reconnect vacuum hose and go to next step.

102) Check EGR Vacuum & Vent Solenoid Vacuum Hoses Disconnect solenoid vacuum hose to be checked. Inspect vacuum hose for obstructions, cracks and kinks. Replace vacuum hose as necessary. Clear codes and repeat QUICK TEST. If vacuum hose is okay, reconnect vacuum hoses and go to next step.

103) Check EGR Vacuum & Vent Solenoids & Circuits For Intermittent Fault Turn ignition off. Disconnect vacuum hose at EGR valve and connect vacuum pump to disconnected hose. Start engine and allow it to idle. Observe vacuum pump for increased vacuum while performing the following

1. Lightly tap on EGR vacuum and EGR vent solenoids (to simulate road shock).
2. Wiggle EGR vacuum and EGR vent solenoid wiring harness connectors.

If vacuum reading increased, isolate fault and repair as necessary. Clear codes and repeat QUICK TEST. If vacuum reading did not increase, fault cannot be duplicated at this time. Testing is complete.

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

1. TP sensor.
2. Wiring harness circuits (TP, SIG RTN and VREF).
3. Powertrain Control Module (PCM).

Normal range of throttle angle measurement for TP sensor is 0-85 degrees. To pass QUICK TEST procedure, range of throttle rotation (in degrees) must be within 3 percent of specification. (Scheme 12)

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

1. Idle speed.
2. Binding throttle shaft or linkage.
3. TP sensor not seated.

TEST PIN NO. 26 (VREF) WIRE COLOR IDENTIFICATION

TEST PIN NO. 46 (SIG RTN) WIRE COLOR IDENTIFICATION

TEST PIN NO. 47 (TP) WIRE COLOR IDENTIFICATION

TP Sensor Specification Chart (DH2). Scheme 12

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

1. Binding throttle linkage.
2. TP sensor not seated correctly.
3. Faulty TP sensor.
4. Faulty Powertrain Control Module (PCM).

Perform KOER SELF-TEST. Check for Code 327. If Code 327 is present with Code 121, service Code 327 and repeat QUICK TEST. If Code 327 is not present with Code 121, go to next step.

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

3) Code 123: Attempt To Generate Code 122 Code 123 indicates TP sensor signal is more than self-test maximum value. Possible causes for this fault are

1. TP sensor not seated properly.
2. Faulty TP sensor.
3. Short circuit to power.
4. Faulty PCM.

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

4) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. If reading is 4-6 volts, replace TP sensor 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. Leave TP sensor disconnected. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 47 and test pins No. 26 and 57 at breakout box. If any resistance is less than 10,000 ohms, repair short circuit in wiring harness. Remove breakout box, reconnect all components, and repeat QUICK TEST. If both resistances are 10,000 ohms or more, replace PCM. Remove breakout box, reconnect all components, 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 122: Attempt To Generate Code 123 Or 121 Code 122 indicates TP signal is less than minimum self-test value. (Scheme 12) Possible causes for this fault are

1. TP sensor not seated correctly.
2. Faulty TP sensor.
3. Open circuit in wiring harness.
4. Grounded circuit in wiring harness.
5. Faulty PCM.

Turn ignition off. Disconnect TP sensor from harness. Install a jumper wire between VREF and TP terminals at TP sensor wiring harness connector. Perform KOEO SELF-TEST. If no codes are generated, remove jumper wire and go to step 13). If Codes 123 and 121 are not present, remove jumper wire and go to next step. If either Code 123 or 121 is displayed, replace TP sensor and repeat QUICK TEST.

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

12) Check TP Sensor Circuit Continuity Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between TP terminal at TP sensor wiring harness connector and test pin No. 47. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

13) Check TP Circuit For Shorts To Ground Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. With breakout box installed and PCM disconnected, measure resistance between test pin No. 47 and test pins No. 40, 46 and 60 at breakout box. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace PCM. Remove breakout box, reconnect all components, 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 167: Repeat Dynamic Response Test KOER Code 167 indicates TP sensor did not exceed 25 percent 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 a WOT is performed during dynamic response portion of test. If Code 167 is still present, go to next step. If Code 167 is not present, system is unable to duplicate Code 167 at this time. Service any other KOER codes. If no other service codes are present, testing is complete.

21) Check TP Sensor Movement During Dynamic Response Test Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 46 and 47 at breakout box. Perform KOER SELF-TEST and ensure proper WOT is completed during dynamic response test. If DVOM reading exceeds 3.5 volts during dynamic response test, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If reading does not exceed 3.5 volts, ensure TP sensor is correctly installed and adjusted. If TP sensor is correctly installed and adjusted, replace TP sensor. Remove breakout box, reconnect all components, and 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 123 This test monitors TP sensor under simulated road conditions. Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Connect DVOM or diagnostic tester to STO terminal of Data Link Connector (DLC). While slowly opening throttle to WOT, observe DVOM or diagnostic tester for indication of fault. Slowly bring throttle to closed position. Lightly tap TP sensor and wiggle harness connector. This test checks for open or short in TP sensor and wiring harness. If no fault is indicated, go to step 92). If fault is indicated, go to next step.

91) Measure TP Circuit Voltage While Exercising TP Sensor Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Stay in wiggle test (as in previous step). Connect DVOM between test pins No. 47 and 46. Set DVOM on 20-volt scale. With ignition on and engine off, observe DVOM and repeat step 90). If fault occurs at less than 4.25 volts, inspect TP sensor connectors and terminals. If connectors and terminals are okay, replace TP sensor, clear codes and repeat QUICK TEST. If fault does not occur at less than 4.25 volts, TP sensor over-travel may have caused Continuous Memory Code 123. TP sensor 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 TP sensor wiring harness connector to firewall and from firewall to PCM 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 PCM & Harness Connectors Turn ignition off. Disconnect PCM 60-pin connector from breakout box. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Clear codes from PCM memory, and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 123 testing is complete.

94) Continuous Memory Code 122 Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Connect DVOM or diagnostic tester to STO terminal of Data Link Connector (DLC). Observe DVOM or diagnostic tester for indication of fault while performing the following

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

If fault is indicated, disconnect TP sensor. Inspect connectors and terminals. If connectors and terminals are okay, replace TP sensor. Clear codes from PCM 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 TP sensor wiring harness connector to firewall and from firewall to PCM while observing analog voltmeter or scan tester. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes from PCM memory, and repeat QUICK TEST. If no fault is indicated, go to next step.

96) Check PCM & Harness Connectors Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Clear codes from PCM memory, and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 122 testing is complete.

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

1. Vehicle Speed Sensor (VSS).
2. VSS wiring harness circuits.
3. Powertrain Control Module (PCM).

Vehicle Speed Sensor Circuit (DP1). Scheme 13

TEST PIN NO. 3 (VSS +) WIRE COLOR IDENTIFICATION

TEST PIN NO. 6 (VSS -) WIRE COLOR IDENTIFICATION

CID signal provides PCM information for fuel injector synchronization. The CID signal originates from Camshaft Position (CMP) sensor.

Enter this CIRCUIT TEST only when instructed during QUICK TEST. This test is only intended to diagnose

1. CID +, CID -, CID, SIG RTN and VREF wiring harness circuits.
2. Camshaft Position (CMP) sensor.
3. Crankshaft Position (CKP) sensor.
4. Powertrain Control Module (PCM).

CID Wiring Harness Circuits (DR1). Scheme 14

1) Continuous Memory Code 214 Code 214 indicates error has been detected in CID sensor input signal. Error could be due to a hard fault or an intermittent fault. Possible causes for this fault are

1. Open or shorted wiring harness.
2. Faulty CMP sensor.
3. Faulty ICM.
4. Faulty PCM.

Start engine. If engine starts, go to next step. If engine does not start, go to step 10).

2) Attempt To Generate Code 214 Clear continuous memory codes. Start engine. Raise engine speed to 1500 RPM for 10 seconds. Return to idle speed. Raise speed to 1500 RPM for 10 seconds again. Turn ignition off. Perform KOEO SELF-TEST. If Continuous Memory Code 214 is not present, go to step 20). If Continuous Memory Code 214 is present, go to next step.

3) Check Continuity Of CID Circuits Disconnect CMP sensor. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between CID or CID (+) test pin at breakout box and CID or CID (+) terminal at sensor 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 next step.

4) Check CID Circuit For Short To Power Turn ignition off. Ensure PCM and CMP sensor are disconnected. Ensure scan tester is not connected to vehicle. Turn ignition on. Measure voltage between CID or CID (+) test pin and test pin No. 40 at breakout box. If voltage is less than 1.0 volt, go to next step. If voltage is 1.0 volt or more, repair short to power in CID circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

5) Check CID Circuit For Short To Ground Turn ignition off. Ensure PCM and CMP sensor are disconnected. Measure resistance between CID or CID (+) test pin and pins No. 16, 40 and 46 at breakout box. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are more than 10,000 ohms, go to step 7).

6) Check VPWR Circuit Voltage Ensure PCM and CMP are disconnected. Turn ignition on. Measure voltage between VPWR terminal at CMP sensor and negative battery terminal. If voltage is less than 10.5 volts, repair open in VREF circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step.

7) Check For Shorts In PCM Turn ignition off. Ensure CMP is disconnected. Connect PCM to breakout box. Measure resistance between test pin No. 24 and test pins No. 16, 37, 40, 46, 57 and 60 at breakout box. If all readings are more than 500 ohms, go to next step. If any reading is 500 ohms or less, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST.

8) Check CMP Sensor Output Turn ignition off. Reconnect CMP sensor wiring harness connector. Set DVOM on AC scale. Start engine. Measure voltage between test pins No. 24 and 40 while varying engine RPM. If voltage varies more than 0.1 volt, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage does not vary more than 0.1 volt, replace CMP sensor. Remove breakout box, reconnect all components, and repeat QUICK TEST.

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) Check VPWR At CMP Sensor Turn ignition off. Disconnect CMP sensor. Turn ignition on. Measure voltage between VPWR terminal at CMP sensor wiring harness connector and negative battery terminal. If voltage is less than 10.5 volts, repair open in VREF circuit and repeat QUICK TEST. If voltage is 10.5 volts or more, VPWR circuit is okay. Go to IGNITION SYSTEMS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 10) to step 20). No test procedures have been omitted.

20) Check CID Circuit Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe analog VOM or diagnostic tester for indication of fault while performing following: grasp wiring harness near PCM wiring harness connector while observing VOM or diagnostic tester for fault indication. Shake and bend small sections of harness, working from PCM toward sensor. If fault is indicated, isolate fault and repair as necessary. Repeat QUICK TEST. If no fault is indicated, problem 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. This test is intended to diagnose a faulty BOO switch circuit or PCM. 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 (FD1). Scheme 15

TEST PIN NO. 2 (BOO) WIRE COLOR IDENTIFICATION

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

1. Brake pedal not applied during self-test.
2. Brake pedal applied during entire self-test.
3. Open brakelight circuit.
4. Short to ground or power.
5. Faulty brakelight switch.
6. Faulty Powertrain Control Module (PCM).

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

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

3) Check For BOO Switch Circuit Cycling Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure voltage between BOO test pin (No. 2) and test pin No. 40 while applying and releasing brake. If voltage cycles, replace PCM and repeat QUICK TEST. If voltage does not cycle, repair open circuit in BOO switch circuit between PCM and BOO switch connection to brakelight circuit. Repeat QUICK TEST.

4) Check For Power To Brakelight 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 more 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 next step. 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 PCM Turn ignition off. Disconnect PCM. Turn ignition on. Check brakelights. If brakelights are on, go to next step. If brakelights are off, replace PCM and repeat QUICK TEST.

7) Check For Short To Power In Shift Lock Actuator Turn ignition off. Ensure PCM and brakelight switch are disconnected. Disconnect shift lock actuator, cruise control module and ABS module (if equipped). Turn ignition on. If brakelights are still on, repair short to power in BOO or STOPLAMP circuit and repeat QUICK TEST. If brakelights are off, repair short circuit in shift lock actuator circuit, cruise control system circuit or ABS circuit. Reconnect all components and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 536: Check For Proper Brakelight Switch Installation Code 536 indicates a BOO circuit failure. Possible causes for this fault are

1. Brakelight switch installed improperly.
2. Open brakelight circuit.
3. Short to ground or power.
4. Faulty brakelight switch.
5. Faulty brakelight switch ground connection.

Check brakelight switch for proper installation (alignment with brake pedal, corrosion or frayed wires). If brakelight switch is okay, go to next step. If brakelight switch is not okay, repair as necessary. Clear codes and repeat QUICK TEST.

91) Check Brakelight Switch Ground Check brakelight switch ground connection. Also, check brakelight connector wires for corrosion or damage. Repair as necessary. Clear codes and repeat QUICK TEST. If connector and wires are okay, go to next step.

92) Check Brakelight BOO Circuits For Short To Power Turn ignition on. Observe brakelights. With brake pedal released, wiggle brakelight BOO circuit wires and connectors. If brakelights flash, isolate short to power and repair as necessary. Clear codes and repeat QUICK TEST. If brakelights do not flash, go to next step.

93) Check Brakelight Circuit Continuity Turn ignition off. Depress and hold-down brake pedal. Observe brakelights and wiggle brakelight circuit wires and connectors. Also, lightly tap on brakelight switch (to simulate road shock). If brakelights flash or go off, isolate open in brakelight circuit and repair as necessary. Clear codes and repeat QUICK TEST. If brakelights stay on (normal operation), go to next step.

94) Check BOO Circuit Continuity Turn ignition off. Release brake pedal. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Connect DVOM between BOO test pin (No. 2) at breakout box and BOO terminal at brakelight switch. Observe DVOM and wiggle BOO circuit wires and connectors. If resistance at anytime was more than 5 ohms, isolate open in BOO circuit and repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance was 5 ohms or less at all times, fault is intermittent and cannot be duplicated at this time. Testing is complete.

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

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

1. Blower (BLR) motor input circuit.
2. Daytime Running Lights (DRL) input circuit.
3. Headlight (HDL) input circuit.
4. Rear window Defroster (DEF) input circuit.
5. Powertrain Control Module (PCM).

SWITCH CIRCUIT LOGIC

Electrical Load Input Circuit (FE1). Scheme 16

TEST PIN WIRE COLOR IDENTIFICATION

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 PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Turn climate control motor switch to low-speed position "1" or "2". Measure voltage between chassis ground and test pin No. 29 at breakout box. If voltage is not 10-17 volts, go to step 13). If voltage is 10-17 volts, go to next step.

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 chassis ground and test pin No. 29 at breakout box. If voltage is less than 1.5 volts, replace PCM and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.

12) Check Blower Circuit For Short To Power Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 29 and test pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check for damaged blower motor or relay. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

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. 29. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.

14) Check Blower Circuit For Short To Ground Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 29 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check for damaged blower motor switch or relay. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

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 PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Apply parking brake. Turn ignition on. Turn headlights on. Turn accessories off. Measure voltage between chassis ground and test pin No. 14 at breakout box. If voltage is not 10-17 volts, go to step 23). If voltage is 10-17 volts, go to next step.

21) Check DRL Circuit Voltage (Headlights Off) Turn headlights off. Release parking brake. Turn ignition on. Measure voltage between chassis ground and test pin No. 14 at breakout box. If voltage is less than 1.5 volts, replace PCM. Remove breakout box and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.

22) Check DRL Circuit For Short To Power Turn ignition off. Ensure PCM is disconnected. Disconnect daytime running lights relay. Measure resistance between test pin No. 14 and pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check daytime running lights module for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, 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. 14 at breakout box. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.

24) Check DRL Circuit For Short To Ground Turn ignition off. Measure resistance between test pin No. 14 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check daytime running lights module for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, 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 off. Remove PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn all accessories off. Turn ignition on. Measure voltage between chassis ground and test pin No. 42 at breakout box. If voltage is 1.5 volts or more, go to step 34). If voltage is less than 1.5 volts, go to next step.

31) Check Headlight Circuit Voltage (Headlights On) Turn all accessories off. Turn ignition on. Turn headlights on. Measure voltage between chassis ground and test pin No. 42 at breakout box. If voltage is 10-17 volts, replace PCM. Remove breakout box and confirm idle speed fault has been corrected. If voltage is not 10-17 volts, go to next step.

32) Check HDL Circuit Continuity Turn ignition off. Disconnect headlight relay. Measure resistance between HDL terminal at power distribution box and test pin No. 42 at breakout box. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.

33) Check HDL Circuit For Short To Ground Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 42 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check headlight switch for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, 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. 42 and test pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check headlight switch for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, 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 PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Measure voltage between chassis ground and test pin No. 23 at breakout box. If voltage is 10-17 volts, go to next step. 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 chassis ground and test pin No. 23 at breakout box. If voltage is less than 3 volts, replace PCM. Remove breakout box and confirm idle speed fault has been corrected. If voltage is 3 volts or more, go to next step.

42) Check DEF Circuit For Short To Power Turn ignition off. Disconnect rear window defroster relay. Measure resistance between test pin No. 23 and test pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check DEF switch or relay for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, 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. 23 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, 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. 23 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check DEF switch and relay circuit for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

The PSP switch is a normally open switch that closes as pressure in the power steering system increases.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Some vehicles may not have power steering, but PCM may be equipped with PSP switch software strategy. If a KOEO Code 519 is displayed, check if vehicle is equipped with power steering. If vehicle is not equipped with power steering, disregard Code 519. This test is only intended to diagnose

1. Power Steering Pressure (PSP) switch.
2. PSP and SIG RTN wiring harness circuits.
3. Powertrain Control Module (PCM).

To prevent replacement of good components, be aware the 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 (PSP) Switch Circuit (FF1). Scheme 17

PSP SWITCH TEST PIN NUMBER IDENTIFICATION

TEST PIN NO. 28 (PSP) WIRE COLOR IDENTIFICATION

TEST PIN NO. 46 (SIG RTN) WIRE COLOR IDENTIFICATION

1) KOEO Code 519: Attempt To Eliminate Code Code 519 indicates PSP switch circuit is open. Possible causes for this fault are

1. Damaged PSP switch.
2. Open circuit in wiring harness.
3. Faulty PCM.

Turn ignition off. Disconnect PSP switch. Install jumper wire between PSP terminal and SIG RTN terminal at wiring harness connector. Repeat KOEO SELF-TEST. If Code 519 is not displayed, replace PSP switch and repeat QUICK TEST. If Code 519 is displayed, remove jumper wire and go to next step.

2) Check Continuity Of PSP Circuits Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 46 and SIG RTN terminal at PSP switch wiring harness connector. Also measure resistance between PSP test pin at breakout box and PSP terminal at switch wiring harness connector. If both readings are less than 5 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If readings are 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

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

4) Check PSP Switch Circuits For Shorts Turn ignition off. Disconnect PSP switch wiring harness connector. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between PSP test pin at breakout box and test pin No. 46 at breakout box. If resistance is 10,000 ohms or less, repair short in harness and recheck symptom. If resistance is more than 10,000 ohms, replace PCM and recheck symptom.

5) KOER Code 521 Disregard this code if vehicle does not have power steering. Code 521 indicates PSP switch did not change states due to open or closed switch. Possible causes for this fault are

1. Damaged PSP switch.
2. Open or shorted circuit in wiring harness.
3. Front wheels turned but not centered.
4. Faulty PCM.

If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and then returned to center, go to next step. If steering wheel was not turned, repeat QUICK TEST.

6) Check PCM Open Circuit Identifying Capabilities Turn ignition off. Disconnect PSP switch. Perform KOEO SELF-TEST. If Code 519 is present, go to step 8). If Code 519 is not present, go to next step.

7) Check PSP Switch Circuits For Shorts Turn ignition off. Disconnect PSP switch. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between PSP test pin and test pin No. 46 at breakout box. If resistance is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST.

8) Check PSP Switch Position Comparison Turn ignition off. Connect PCM connector to breakout box. With PSP switch connected, turn ignition on. Measure and record resistance between PSP test pin and test pin No. 46 at breakout box. Start engine. Measure and record resistance between PSP test pin 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 next step. If reading is not as described, replace PSP switch and repeat QUICK TEST.

9) Check PSP Switch With Engine Running (Load & No Load) Connect PSP switch. Start engine, and allow it to idle. Measure resistance between PSP test pin 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), PSP switch system is okay. Testing is complete. If reading does not change as indicated, replace PSP switch. Repeat QUICK TEST.

10) Code 519: Attempt To Eliminate Code 519 Disregard this code if vehicle does not have power steering. Code 519 indicates PSP switch circuit is closed. Possible causes for this fault are

1. Damaged PSP switch.
2. Open or shorted circuit in wiring harness.
3. Faulty PCM.

Turn ignition off. Disconnect PSP switch connector. Repeat KOEO SELF-TEST. Measure resistance between PSP test pin and test pin No. 46 at breakout box. If Code 519 is not present, replace PSP switch. Repeat QUICK TEST. If Code 519 is present, go to next step.

11) Check PSP Circuit For Short Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between PSP test pin and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and recheck symptom. If reading is more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and recheck symptom.

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 PSP Switch Operation Connect tachometer, and start engine. Allow engine to idle in Park or Neutral. Disconnect PSP switch connector. Using jumper wire, connect PSP switch wiring harness connector terminals. If RPM increases, replace PSP switch and recheck symptom. If RPM does not increase, go to next step.

16) Check Continuity Of PSP Switch Circuits Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Measure resistance between test pin No. 46 and SIG RTN terminal at PSP switch wiring harness connector. Also, measure resistance between PSP switch test pin at breakout box and PSP terminal at PSP switch wiring harness connector. If both readings are less than 5 ohms, replace PCM. Remove breakout box, reconnect all components, and recheck symptom. If any reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, 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 Code 521 Disregard this code if vehicle does not have power steering. Code 521 indicates PSP switch did not change states due to open or closed switch. Possible causes for this fault are

1. Damaged PSP switch.
2. Open or shorted circuit in wiring harness.
3. Front wheels turned but not centered.
4. Faulty PCM.

If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and then returned to center, go to next step. If steering wheel was not turned, repeat QUICK TEST.

21) Check PCM Closed Circuit Identifying Capabilities Turn ignition off. Disconnect PSP switch. Connect jumper wire between PSP terminal and SIG RTN terminal at PSP 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 next step.

22) Check Continuity Of PSP Switch Circuits Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between PSP test pin at breakout box and PSP terminal at PSP switch wiring harness connector. Also, measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at PSP switch wiring harness connector. If both readings are less than 5 ohms, replace PCM and repeat QUICK TEST. If any reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

23) Check PSP Switch Position Comparison Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Reconnect PSP switch. Turn ignition on. Measure resistance between PSP switch test pin and test pin No. 46 at breakout box. Start engine. If reading remains less than 10 ohms difference between key on engine off and key on engine running, go to next step. If reading is not as described, replace PSP switch and repeat QUICK TEST.

24) Check PSP Switch With Engine Running (Load & No Load) Start engine, and allow it to idle. Measure resistance between PSP switch test pin 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 30 ohms to infinity and then returns to 30 ohms or less (when steering wheel is centered), PSP switch system is okay. Testing is complete. If reading does not change as indicated, replace PSP switch. Repeat QUICK TEST.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. To prevent replacement of good components, be aware the following non-EEC related areas may be at fault

1. Excessive blow-by.
2. PCV malfunction.
3. Vacuum leaks.
4. Incorrect fuel pressure.
5. Throttle binding.
6. Improper fuel pressure.
7. Idle air control solenoid. This test is only intended to diagnose
8. Throttle Position Sensor (TPS).
9. Mass Airflow (MAF) sensor.
10. Intake Air Temperature (IAT) sensor.
11. Fuel injectors.

1) Check For Idle Air Codes Code 121 indicates TPS is inconsistent with MAF value. Code 124 indicates TPS value is higher than expected. Code 125 indicates TPS value is lower than expected. Turn ignition on. Repeat KOEO SELF-TEST. If Code 411 or 412 is present, perform appropriate circuit test. See DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS. If Code 411 or 412 is not present, go to next step.

2) Throttle Position (TP) Sensor: TP Sensor Integrity Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Connect DVOM to test pins No. 46 and 47 at breakout box. Turn ignition on. Slowly apply throttle to WOT, and release to closed position. Voltage should change smoothly from 0.4-4.5 volts. See CIRCUIT TEST DH for schematics and specific engine values. If voltage change is incorrect or erratic, ensure TP sensor is properly installed. If TP sensor is properly installed, replace TP sensor. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage is okay, go to step 8) for Code 121 or next step for all other codes.

3) Check Idle Ensure idle is correct. If idle is correct, go to next step. If idle is incorrect, see IDLE SPEED in ADJUSTMENTS article in the ENGINE PERFORMANCE section.

4) Check Throttle Body Ensure idle is correct. Check throttle and/or cruise control linkage for binding and rough operation. Inspect throttle body for sludge build-up. Check engine vacuum hoses. Refer to Vehicle Emission Control Information (VECI) decal for proper vacuum hose routing. Check for air leak between ISC solenoid and MAF sensor. If problems are found, repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST. If no problems are found, go to next step.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 6). No test procedures have been omitted.

6) Check IAT Sensor Ensure ambient temperature is more than 50°F (10°C) before performing this test. Also, check and repair any air leaks in front of IAT sensor. Turn ignition off. Connect breakout box to PCM. Set DVOM to 20-volt scale. Connect DVOM to test pins No. 25 and 46. Start engine, and let it idle. Observe voltage as engine warms up. See CIRCUIT TEST DA for voltage specifications. If voltage decreases smoothly and stabilizes when engine reaches operating conditions, system is operating properly at this time. Testing is complete. If voltage does not decrease smoothly and stabilize after engine reaches operating conditions, replace IAT sensor and repeat QUICK TEST.

7) Continuous Memory Code 184 & 185: Inspect MAF Sensor Code 184 indicates MAF sensor signal is higher than expected. Code 185 indicates MAF sensor signal is lower than expected. Turn ignition off. Check for air leaks between Idle Air Control (IAC) solenoid and MAF sensor. Inspect MAF sensor for oil contamination caused by excessive blow-by or malfunctioning PCV. If problems are found, repair as necessary. Clear codes and repeat QUICK TEST. If no problems are found, go to step 10).

8) Check MAF Sensor Circuit Voltage Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Start engine, and warm it to normal operating temperature. Measure voltage between test pin No. 50 and test pin No. 40 or 60 at breakout box. If voltage is not within specification, replace MAF sensor. Remove breakout box, reconnect all components, and repeat QUICK TEST. See MAF SENSOR DATA table. If voltage is within acceptable range, system is operating normally at this time. Sometime during the last 80 warm-up cycles, MAF sensor signal was out of range. See SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE section.

MAF SENSOR DATA

9) Continuous Memory Code 186 & 187: Visual Vacuum Checks Code 186 indicates pulse width is longer than expected (rich). Code 187 indicates pulse width is shorter than expected (lean). Inspect air cleaner and air inlet duct. Replace or repair an necessary. Check for unmetered air leaks between MAF sensor and IAC solenoid. Check all engine vacuum hoses for damage, blockage and improper routing. Repair as necessary, and repeat QUICK TEST. If all checks are okay, go to next step.

10) Check Fuel Pressure Turn ignition off. Install fuel pressure gauge. Ensure vacuum hose is connected to fuel pressure regulator (if applicable). Start engine, and run it at idle. If fuel pressure is within specification, go to next step. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is not within specifications, repair as necessary. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

FUEL PRESSURE SPECIFICATIONS

11) Verify Fuel Pressure Retention Ability Turn ignition on. If fuel pressure remains at specification for 60 seconds, go to CIRCUIT TEST HB, step 2) (Flex Fuel) or next step (except Flex Fuel). If fuel pressure does not remain at specification, repair fuel delivery system as necessary. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

12) Cylinder Balance Test Perform KOER SELF-TEST. After last code, wait 5-10 seconds, and then goose throttle lightly (not wide open throttle). This will activate cylinder balance test. If Code 90 is present after test, go back to step 7). If Code 90 is not present after test, go to CIRCUIT TEST HB, step 4).

Perform this test when instructed during QUICK TEST or if directed by other test procedures. (Fuel-contaminated engine oil may affect Codes 172 and 173. 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. HO2S and sensor connection.
2. Vacuum systems.
3. Fuel injector and/or fuel injector circuitry.
4. Powertrain Control Module (PCM).
5. Electrical circuits (HO2S, HO2S GND, INJ 1-8, VPWR and SIG RTN).

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

1. Ignition system.
2. Faulty evaporative emission system.
3. EGR and/or PCV system.
4. Air intake system.
5. Engine oil contamination.
6. Fuel system.
7. Intake leaks.
8. Exhaust system leaks or restriction.
9. Electrical system.
10. Engine cooling system.

INDIVIDUAL INJECTOR RESISTANCE

FUEL PRESSURE SPECIFICATIONS

Test Schematic (H1). Scheme 18

TEST PIN NO. 43 WIRE COLOR IDENTIFICATION

TEST PIN NO. 44 WIRE COLOR IDENTIFICATION

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 KOEO and KOER SELF-TEST. Service ignition continuous memory code (if present) before servicing KOER codes. If vehicle is a no-start, install PCV valve and go to next step. If Code 139, 144, 171, 176 or 177 is present, go to next step. 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. Release fuel pressure. 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. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is within specification, go to next step. If pressure is not within specification, go to FUEL SYSTEM in the SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

3) Check System Ability To Hold Fuel Pressure Turn ignition on. Check fuel system for leaks. Repair or replace as necessary. If fuel system does not leak and pressure remains at specification for 60 seconds, go to next step (no-starts), step 5) (MFI) or step 6) (SFI).

4) Fuel Delivery Test Release fuel system pressure. With fuel pressure gauge installed, pressurize fuel system as in step 1). Disconnect inertia switch. Crank engine for 5 seconds. If fuel pressure drop is greater than 5 psi after 5 seconds of cranking, 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 MFI or step 8) for SFI.

5) Cylinder Balance Test (MFI) 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. IAC 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 172, 136 or 176, step 24) for Codes 173, 137 or 177 or step 14) for all others.

6) Cylinder Balance Test (SFI) 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 table. If KOEO Code 244 is output, cylinder balance test has been aborted. Go to CIRCUIT TEST DR. Code 538 indicates throttle was touched when test was run 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 DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS for instruction. For Code 172, 136 or 176, go to step 13). For Code 173, 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 (MFI) Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance of injector bank No. 1 between test pins No. 37 and 58 at breakout box. Also, measure resistance of injector bank No. 2 between test pins No. 37 and 59 at breakout box. Record resistances. 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.

8) Check Injector & Harness Resistance (SFI) Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure and record resistance between suspected injector circuit test pin and test pin No. 37. For no-start, measure and record resistance between injector circuit test pin and test pin No. 37. (Scheme 18) Refer to INDIVIDUAL INJECTOR 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 next step 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. (Scheme 18) Measure resistance between injector test pin(s) at breakout box and same injector circuit terminal at each injector wiring harness connector. If each reading is less than 5 ohms, go to next step. If each reading 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. With breakout box installed and PCM disconnected, disconnect fuel injector wiring harness connector. (Scheme 18) Measure resistance between injector test pin(s) and test pins No. 37, 40, 46, 57 and 60. Also, 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 (SFI) or go to next step (MFI). 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 PCM. 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 table. If all injectors are within specification, go to next step. 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 PCM to breakout box. Use a non-powered 12-volt test light, and connect as follows

1. 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 PCM. Reconnect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 14). No test procedures have been omitted.

14) Check HO2S Integrity A HO2S which is always lean, slow to switch or does not switch could be caused by

1. Moisture inside HO2S or connector causing a short to ground.
2. HO2S coated with contaminants.
3. HO2S circuit open.
4. HO2S circuit shorted to ground.

Turn ignition off. Inspect HO2S wiring harness for damage. Inspect HO2S 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 16). If no codes are present, go to step 21).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 16). No test procedures have been omitted.

16) Check HO2S Purpose of this test is to verify HO2S can generate a voltage signal of greater than 0.5 volt during KOER SELF-TEST. Vacuum or air leaks in non-EEC-IV areas could cause Code 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. Unmetered air between MAF sensor and throttle body.
6. Lead-contaminated HO2S.

Turn ignition off. Disconnect appropriate HO2S from harness. Connect DVOM between HO2S terminal and HO2S GND or HO2S GND terminal at HO2S wiring harness connector. Run engine at 2000 RPM for 2 minutes. Repeat KOER SELF-TEST and monitor HO2S voltage. If voltage is 0.5 volt or more at end of self-test, go to next step. If voltage is less than 0.5 volt, replace HO2S and repeat QUICK TEST.

17) Check Continuity Of HO2S Ground Circuits Turn ignition off. Install breakout box, leaving PCM disconnected. Disconnect suspect HO2S wiring harness connector. Inspect connector for damage, moisture and corrosion. Repair as necessary. Measure resistance between HO2S test pin at breakout box and HO2S terminal at sensor wiring harness connector. Measure resistance between SIG RTN test pin at breakout box and SIG RTN terminal at sensor wiring harness connector. Where applicable, measure resistance between HO2S GND and SIG RTN at breakout box. Go to next step 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 HO2S Circuit For Short To Ground Turn ignition off. Leave breakout box installed and PCM disconnected. Disconnect HO2S. Measure resistance between HO2S circuit test pin and test pins No. 40, 46 and 49 at breakout box. If any reading is less than 10,000 ohms, repair short to ground. Drive vehicle at 55 MPH for 5 minutes and repeat QUICK TEST. If reading is 10,000 ohms or more, go to next step.

19) Check HO2S For Short To Ground Ensure ignition is off and PCM is disconnected. With HO2S disconnected, measure resistance between PWR GND and HO2S terminal at HO2S connector. Also measure resistance between HO2S GND and/or SIG RTN terminal at sensor wiring harness connector. If resistance is less than 10,000 ohms, replace HO2S. Drive vehicle for 5 miles at 55 MPH and repeat QUICK TEST. If resistance is 10,000 ohms or more, perform following procedure as applicable.

1. For Codes 139, 144, 171, 174, 175 and 178, go to step 90).
2. For all other codes, replace PCM. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 19) to step 21). No test procedures have been omitted.

21) Check Resistance Of HO2S Heating Element Turn ignition off. Disconnect suspect HO2S. Inspect both ends of connector for damage, moisture and corrosion. Repair as necessary. Measure resistance between IGNITION RUN circuit and PWR GND circuit at HO2S connector. Hot to warm engine resistance should be 5-30 ohms. Cold engine temperature resistance is 2-5 ohms. If resistance is within specification, go to next step. If resistance is not as specified, replace HO2S and repeat QUICK TEST.

22) Check For Power At HO2S Harness Connector Disconnect HO2S. Turn ignition on. Measure voltage between IGNITION RUN and PWR GND circuits at HO2S wiring harness connector. If voltage is 10.5 volts or more, HO2S system and fuel delivery are okay. HO2S may have cooled before KOER SELF-TEST. If driveability symptom continues, fault is in area common to all cylinders (vacuum leak, fuel contamination, EGR, ignition system, etc.). See TESTS W/O CODES article in the ENGINE PERFORMANCE section. If voltage is less than 10.5 volts, go to next step.

23) Check Continuity Of Power Ground Circuit Turn ignition off. Measure resistance between PWR GND circuit at HO2S 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) Diagnostic Test Code 173: Check HO2S SIGNAL For Short To Power HO2S continuously rich could be caused by

1. Moisture inside wiring harness causing short to power.
2. HO2S shorted to power.

Turn ignition off. Disconnect HO2S. Inspect connector for damage and repair as necessary. Turn ignition on. Measure voltage between HO2S and PWR GND terminal at HO2S 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 next step.

25) Check For Short To Power Turn ignition off. Disconnect HO2S. Inspect wiring harness for damage and repair as necessary. Disconnect PCM 60-pin connector. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect suspect HO2S. Measure resistance between VPWR test pin and HO2S SIG test pin at breakout box. If reading is 10,000 ohms or more, replace PCM. Remove breakout box, and reconnect all components. Drive vehicle 5 miles at 55 MPH. Repeat QUICK TEST. If reading is less than 10,000 ohms, repair short circuit. Remove breakout box, and reconnect all components. Drive vehicle 5 miles at 55 MPH. Repeat QUICK TEST.

26) Check HO2S For Short To IGNITION RUN Circuit Turn ignition off. Disconnect HO2S. Measure resistance between IGNITION RUN terminal and HO2S terminal at HO2S wiring harness connector. If resistance is 10,000 ohms or more, go to next step for Code 173 or step 30) for other codes. If resistance is less than 10,000 ohms, replace HO2S. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST.

27) Attempt To Generate Code 172 Turn ignition off. Disconnect HO2S. Using jumper wire, connect HO2S terminal at HO2S wiring harness connector to negative battery terminal. Repeat KOER SELF-TEST. If Code 172 is present, remove jumper wire and go to step 30). If Code 172 is not present, remove jumper wire. Disconnect PCM connector, and inspect it for damage. If connector is okay, replace PCM. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 27) to step 30). No test procedures have been omitted.

30) HO2S Check Turn ignition off. Disconnect HO2S. Connect DVOM to HO2S terminal and HO2S GND or SIG RTN terminal at HO2S connector. Create a vacuum leak to force HO2S to go lean. Remove PCV valve hose. Start engine. Raise engine speed to about 2000 RPM. DVOM should indicate less than 0.4 volt within 30 seconds. If voltage is not as specified, replace HO2S. 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 HO2S to PCM. Wiggle, shake or bend small sections of wiring harness from HO2S GND to PCM. If no fault is indicated, remain in CONTINUOUS MONITOR MODE and go to next step. 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, 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 HO2S 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 HO2S Switching Turn ignition off. Inspect wiring harness for proper routing and insulation. Check for burnt, chaffed or open wires. Repair as necessary. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box. Connect PCM to breakout box. Connect analog voltmeter to suspect HO2S test pin and HO2S GND at breakout box. Test drive vehicle for 5 miles at 55 MPH while observing voltmeter. HO2S should switch from .3 volt to .9 volt within 3 seconds. If HO2S does not switch as described, replace HO2S. Connect all components, and repeat QUICK TEST. If HO2S switches as described, fault cannot be identified or duplicated at this time. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE section.

Perform this test when directed by QUICK TEST. PCM 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.

FUEL PRESSURE SPECIFICATIONS

CIRCUIT TEST HA ACRONYMS

1) Continuous Memory Code 181 This code identifies a lean fuel condition resulting in adaptive fuel strategy enriching fuel system to compensate.

1. Code 181

Indicates single rear HO2S detected a problem and adaptive fuel rich limit has been reached.

1a) Continuous Memory Code 179 This code identifies a rich fuel condition resulting in adaptive fuel strategy leaning fuel system to compensate.

1. Code 179

Indicates rear HO2S detected a problem and adaptive fuel lean limit has been reached at idle. Possible causes for these codes are

1. Incorrect fuel pressure.
2. Faulty fuel injector or circuit.
3. Leaking or restricted air intake.
4. Restricted air or fuel filter.

If other codes are present, repair as necessary. If no other codes are present, go to next step.

2) Check Fuel Pressure Release fuel system pressure. With ignition off, install fuel pressure gauge. Ensure manifold vacuum is connected to fuel pressure regulator. Start engine and allow to idle. If fuel system pressure is not within specification, repair as necessary. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. If fuel system pressure is within specification, go to next step.

3) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from OFF to ON position 3-4 times to pressurize fuel system (DO NOT start engine). If fuel pressure remains at specification for 60 seconds, go to step 6). If fuel pressure does not remain at specification for 60 seconds, repair fuel system as necessary. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 6). No test procedures have been omitted.

6) Cylinder Balance Test (SFI) 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 table. If Code 90 is present, original fault is in ignition system. If Code 90 is not present, go to step 8).

CYLINDER BALANCE TEST SERVICE CODES

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 6) to step 8). No test procedures have been omitted.

8) Check Injector & Circuit Resistance (SFI) Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure and record resistance between suspected injector circuit test pin and test pin No. 37. (Scheme 18) Refer to INDIVIDUAL INJECTOR RESISTANCE table in this circuit test. If each resistance is within specification, go to step 12). If resistance is not as specified, go to next step.

INDIVIDUAL INJECTOR RESISTANCE

9) Check Continuity Of Fuel Injector Circuit Turn ignition off. Disconnect suspect injector wiring harness connector at injector. Measure resistance between test pins No. 37 and 57 at breakout box and each injector VPWR terminal at wiring harness connector. (Scheme 18) 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 next step. 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 Circuit For Short To Power Or Ground Turn ignition off. With breakout box installed and PCM disconnected, disconnect suspect fuel injector wiring harness connector. Measure resistance between injector test pin(s) and test pins No. 37, 40, 46, 57 and 60. Also, 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 (SFI). 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.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 10) to step 12). No test procedures have been omitted.

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

1. 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 PCM. Reconnect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

When ignition switch is in the ON or START position, the PCM connects FUEL PUMP circuit (PCM terminal No. 22) to ground. The fuel pump relay is energized and electrical current flows to the fuel pump. If PCM does not receive ignition PIP signal within 2 seconds, FUEL PUMP circuit is opened and fuel pump operation is terminated. 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 Fuel Shutoff (IFS) switch.
3. Wiring harness circuits (B+, VPWR, FUEL PUMP, GND and POWER-TO-PUMP).
4. Faulty Powertrain Control Module (PCM).

Fuel Pump Monitor Circuit Diagram (J1). Scheme 19

TEST PIN NO. 37/57 (FPM) WIRE COLOR IDENTIFICATION

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

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

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 next step. If reading is less than 10.5 volts, verify IFS 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.

2) Check Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. Set DVOM on 200-ohm scale. On ISO relays, measure resistance between terminals No. 85 and 86. (Scheme 20) On all other relays, measure resistance between VPWR pin and FUEL PUMP circuit pin at fuel pump relay. On all relays, both readings should be 40-85 ohms. Set DVOM to 10-k/ohm scale. On ISO relays, measure resistance between terminal No. 85 and terminals No. 30 and 87. On all other relays, measure resistance between FUEL PUMP circuit terminal and both POWER-TO-PUMP and B+ pins at fuel pump relay. On all relays, if all readings are more than 10,000 ohms, go to next step. If any reading is 10,000 ohms or less, replace fuel pump relay and repeat QUICK TEST.

Identifying Fuel Pump Relay Connector Terminals (J2). Scheme 20

3) Check For Short To Power Turn ignition off. Disconnect fuel pump relay. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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 next step. If voltage is 1.0 volt or more, repair short circuit. Remove breakout box and reconnect all components. Attempt to start vehicle. If vehicle fails to start, replace PCM and repeat QUICK TEST.

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

5) Check Fuel Pump Circuit Continuity Turn ignition off. Leave fuel pump relay and PCM disconnected. Measure resistance between FUEL PUMP circuit at fuel pump relay vehicle wiring harness connector and test pin No. 22 at breakout box. If resistance is less than 5 ohms, replace PCM. Reconnect fuel pump relay and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, 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 542 A KOEO Code 542 indicates one of the following conditions

Test lights and DVOM are useful during diagnosis. For example: with Continuous Memory Code 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, PCM 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 556 is set again, replace fuel pump relay. If only FP voltage goes low, fault is in FP circuit or PCM. To diagnose FP circuit and PCM, connect DVOM between breakout box test pin No. 1 and 22. If voltage goes low as symptom occurs, replace PCM. If voltage stays high as symptom occurs, fault is in FP circuit. For fuel pump secondary circuit Codes 542 and 543, circuits B+, 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 or if directed by other test procedures. This test is only intended to diagnose

1. CANP solenoid.
2. Harness circuits (CANP and VPWR).
3. Powertrain Control Module (PCM).

Canister Purge (CANP) Circuit (KD1). Scheme 21

TEST PIN NO. 11 (CANP) WIRE COLOR IDENTIFICATION

TEST PINS NO. 37 & 57 (VPWR) WIRE COLOR IDENTIFICATION

1) 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 Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. (Scheme 6) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate PCM has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase, depress throttle to WOT 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 7). If CANP circuit voltage cycles, remain in OUTPUT STATE CHECK and go to next step.

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 next step.

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 next step. If vacuum is not released, check hose from CANP solenoid to canister for blockage or kinks. 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 side. Start engine. If vacuum is present at vacuum hose, engine control 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 mechanical cause of low vacuum.

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

1. Faulty CANP solenoid.
2. Open or short circuit in wiring harness circuit.
3. Faulty PCM.

Turn ignition off. Disconnect CANP solenoid connector. Measure CANP solenoid resistance. If resistance is 30-90 ohms, go to next step. If resistance is not 30-90 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 vehicle harness connector and negative battery terminal. If reading is more than 10.5 volts, go to next step. If reading is 10.5 volts or less, repair open circuit and repeat QUICK TEST.

8) Check Continuity Of CANP Circuit Turn ignition off. Disconnect CANP solenoid. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between CANP circuit breakout box test pin (No. 11) and CANP harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

9) Check CANP Circuit For Short To Ground Turn ignition off. Disconnect scan tester from DLC, if applicable. With CANP solenoid disconnected, measure resistance between CANP circuit breakout box test pin (No. 11, 15 or 31) and pins No. 40, 46 and 60. If all readings are more than 10,000 ohms, go to next step. If any reading is 10,000 ohms or less, repair short to ground. Remove breakout box, reconnect all components, and repeat QUICK TEST.

10) Check CANP Circuit For Short To Power Turn ignition off. With CANP solenoid and PCM disconnected, measure resistance between CANP circuit breakout box test pin (No. 11) and test pins No. 37 and 57. If all readings are more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If any reading is 10,000 ohms or less, repair short to power. Remove breakout box, reconnect all components, and repeat QUICK TEST.

The IAC solenoid controls engine idle speed and dashpot functions by regulating the volume of air by-passing the throttle plate. IAC solenoid positioning is determined by signals sent from the PCM. On these models, a thermowax material is also built into the unit to aid operation of IAC solenoid.

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

1. RPM during SELF-TEST mode.
2. IAC solenoid.
3. Wiring harness circuits (IAC and VPWR).
4. Powertrain Control Module (PCM).

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

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

Idle Air Control Circuit (KE1). Scheme 22

TEST PIN NO. 21 (IAC) WIRE COLOR IDENTIFICATION

TEST PINS NO. 37 & 57 (VPWR) WIRE COLOR IDENTIFICATION

1) Code 412: Check For RPM Drop Code 412 indicates engine RPM could not be controlled within upper RPM limit 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 IAC solenoid contaminated.
5. Faulty IAC solenoid.
6. Faulty PCM.
7. Mechanical faults unrelated to EEC-IV which could affect RPM.

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

2) Check For EGR Codes If EGR service Code 213, 327 or 332 is displayed, reconnect IAC solenoid. Go to appropriate KOER SELF-TEST. See DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS. If these codes are not displayed, go to next step.

3) Check For Other Diagnostic Test Codes If Code 172 or 173 is displayed, reconnect IAC solenoid. Go to appropriate KOER SELF-TEST. See DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS. If these codes are not displayed, go to next step.

4) Measure IAC Solenoid Resistance Turn ignition off. Disconnect IAC solenoid. Connect DVOM positive lead to VPWR terminal and negative lead to IAC terminal. (Scheme 23) Measure resistance of IAC solenoid. If resistance is not 6-13 ohms, replace IAC solenoid and repeat QUICK TEST. If resistance is 6-13 ohms, go to next step.

IAC Solenoid Connector (KE2). Scheme 23

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

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

7) Check IAC Circuit Continuity Turn ignition off. Leave IAC solenoid disconnected. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 21 and IAC terminal at IAC vehicle wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

8) Check IAC Circuit For Short To Ground Turn ignition off. Leave IAC solenoid and PCM disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any reading is 10,000 ohms or less, repair short to ground. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are more than 10,000 ohms, go to next step.

9) Check IAC Circuit For Short To Power Leave IAC solenoid and PCM disconnected. Turn ignition on. Measure voltage between breakout box test pin No. 21 and chassis ground. If voltage is 1.0 volt or more, repair short circuit and repeat QUICK TEST. If code or symptom is still present, replace PCM. If voltage is lee than 1.0 volt, go to next step.

10) Check IAC Signal From PCM Turn ignition off. Reconnect IAC solenoid. Connect PCM to breakout box. 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 voltage is 3.0-11.5 volts, go to next step. If voltage is not 3.0-11.5 volts, remove IAC solenoid to confirm that it is not stuck open. If IAC is okay, replace PCM 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 IAC solenoid and inspect for contamination. Clean or replace solenoid as necessary. Repeat QUICK TEST. If code or symptom is still present, replace IAC 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 next step.

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) label.
4. Check for leaks around IAC solenoid (gaskets, etc.).

If any of these items are faulty, service as necessary, and repeat QUICK TEST. If all of these items are okay, remove IAC solenoid and inspect for contamination. Clean or replace solenoid as necessary. Repeat QUICK TEST. If code or symptom is still present, replace IAC solenoid. 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 411 Code 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 (distributor ignition only).
6. Throttle body or IAC solenoid contamination.
7. IAC circuit shorted to ground.
8. Faulty IAC solenoid.

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

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

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

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

17) Check For Internal Short To IAC Solenoid Case Turn ignition off. Disconnect IAC solenoid wiring harness connector. Measure resistance from either IAC terminal pin to IAC solenoid housing. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, replace IAC solenoid. Repeat QUICK TEST.

18) Check IAC Circuit For Short To Ground Turn ignition off. Leave IAC solenoid disconnected. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any reading is 10,000 ohms or less, repair short to ground. Reconnect components, and repeat QUICK TEST. If all readings are more than 10,000 ohms, go to next step.

19) Check IAC Signal From PCM Turn ignition off. Connect PCM to breakout box. Reconnect IAC solenoid. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40. Start engine. Observe DVOM while slowly increasing engine speed to 3000 RPM. If voltage is 3.0-11.5 volts, go to next step. If voltage is not 3.0-11.5 volts, replace PCM and repeat QUICK TEST.

20) Check For Proper Engine Coolant Flow To Idle Air Control-Bypass Air (IAC-BPA) Valve Check the following

1. Verify engine coolant is warming up properly.
2. Check engine coolant level.
3. Check coolant hoses to and from IAC-BPA valve for leaks, blockage and kinks.

If any check is not okay, repair as necessary. Remove breakout box and reconnect PCM. If all checks are okay, remove IAC-BPA valve and inspect it for contamination. Clean or replace IAC-BPA valve as necessary, and repeat QUICK TEST. If code or symptom is still present, replace IAC-BPA valve.

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) Lack Of High Idle With Engine Cold: Verify IAC-BPA Valve Is Not Stuck Closed Turn ignition off. Remove IAC-BPA valve from engine. With IAC-BPA valve at room temperature, blow through air passage. Air should flow freely. If air does not flow freely, replace IAC-BPA valve and check system operation. If air flows freely, no problem is indicated at this time. See SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE section.

The PCM controls cooling fan operation through High Fan Control (HFC) and Low Fan Control (LFC) outputs. HFC relays are normally open. LFC is normally open. Perform this test only when directed here by QUICK TEST or a driveability symptom. This test is only intended to diagnose

1. Wiring harness circuits (LFC, HFC, LFC POWER-TO-FAN, HFC POWER-TO-FAN, IGN START/RUN and GND).
2. LFC and HFC relays.
3. Cooling fan (2-speed).
4. Powertrain Control Module (PCM).

TEST PIN NO. 30 (LFC) WIRE COLOR IDENTIFICATION

TEST PIN NO. 26 (HFC) WIRE COLOR IDENTIFICATION

1) Code 563 Or Code 564: Check For Voltage At LFC/HFC Relay Code 563 indicates faulty HFC circuit. Code 564 indicates faulty LFC circuit. Possible causes for these faults are

1. Open or shorted circuit.
2. Faulty fan relay(s).
3. Faulty PCM.

Turn ignition off. Disconnect LFC and HFC relays. Turn ignition on. Measure voltage between IGNITION START/RUN circuit (Black/White wire) at LFC/HFC relay vehicle wiring harness connector and chassis ground. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check fuse/fuse link and circuit to LFC/HFC. Repair as necessary. If fuse/fuse link and circuit are okay, repair open circuit and repeat QUICK TEST.

2) Enter OUTPUT STATE CHECK Use only VOM or DVOM for this step. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. (Scheme 6) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate PCM has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases to more than 10.5 volts, stay in OUTPUT STATE CHECK and go to next step. If voltage does not increase to at least 10.5 volts, depress throttle to wide open throttle and release. If STO voltage does not increase to at least 10.5 volts, leave equipment connected and go to CIRCUIT TEST QC, step 2).

3) Check For LFC/HFC Circuit Cycling With vehicle still in OUTPUT STATE CHECK, disconnect LFC or HFC relay(s). Connect DVOM positive lead to IGNITION START/RUN circuit. Connect negative test lead to LFC or HFC coil terminal at each relay connector in vehicle wiring harness. Depress throttle to cycle outputs off. Observe DVOM and depress throttle again. For LFC, wait until CHECK ENGINE light flashes once (about 10 seconds). For HFC, wait until CHECK ENGINE light flashes twice (about 15 seconds). Release throttle. LFC/HFC output is now on. To cycle off output, depress and release throttle. If voltage cycles (about a 1-volt change), replace LFC or HFC relay. Remove jumper wire and repeat QUICK TEST. If voltage does not cycle, remove jumper wire and go to step 5).

Note. A/C Pressure Switch (ACPSW) is also known as A/C high pressure cut-off switch.

4) Verify A/C Pressure Switch Medium Pressure Contacts Are Not Closed While still in OUTPUT STATE CHECK and with HFC relays disconnected, disconnect A/C Pressure Switch (ACPSW). Connect DVOM positive lead to IGNITION START/RUN circuit. Connect negative test lead to HFC terminals at each HFC relay vehicle wiring harness connector. Depress throttle to cycle outputs off. Observe DVOM and depress throttle again. Wait until CHECK ENGINE light flashes twice (about 15 seconds). Release throttle. HFC output is now on. To cycle off output, depress and release throttle. If voltage cycles (about a 1-volt change), check ACPSW for closed medium pressure contacts. Replace switch as necessary. If voltage does not cycle, reconnect ACPSW, remove jumper wire and go to next step.

Note. ACPSW switch controls operation of both A/C clutch and engine cooling fan. Contacts for cooling fan portion of ACPSW are normally open. When high side pressure reaches 325 psi (22.9 kg/cm 2 ), switch contacts close. For more information, see appropriate AIR CONDITIONING & HEAT article.

5) Check Continuity Of LFC/HFC Circuit Turn ignition off. Disconnect LFC or HFC relay(s). Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Set DVOM on 200-ohm scale. Perform appropriate following check

1. Code 563 Measure resistance between breakout box HFC test pin and HFC terminal at each HFC relay of vehicle wiring harness connector.
2. Code 564 Measure resistance between breakout box LFC test pin and LFC terminal at LFC relay vehicle wiring harness connector.

For either code, if resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

6) Check LFC/HFC Circuit For Short To Power Disconnect LFC or HFC relay(s). Turn ignition on. Measure voltage between breakout box LFC or HFC test pin and negative battery terminal. If voltage is less than 1.0 volt, go to next step. If voltage is 1.0 volt or more, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If code is still present, replace PCM.

7) Check LFC/HFC Circuit For Short To Ground Turn ignition off. Leave PCM and LFC or HFC relay(s) disconnected. Measure resistance between breakout box LFC or HFC test pin and test pins No. 40 and 60. If resistance is more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, 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) Low-Speed (LFC) And/Or High-Speed (HFC) Cooling Fan Does Not Operate Turn ignition off. Disconnect LFC relay. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between HFC relay terminal at LFC relay vehicle wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to step 13). If voltage is 10.5 volts or less, go to next step.

11) Check For Voltage To HFC Relays Turn ignition off. Disconnect LFC and HFC relays. Turn ignition on. Measure voltage between IGNITION RELAY (BATT +) terminal at each HFC relay of vehicle wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check fuse/fuse link. If fuse/fuse link are okay, repair open circuit and check system operation.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 13). No test procedures have been omitted.

13) Check Circuits From LFC Relay To Fan Turn ignition off. Disconnect LFC relay. Install a jumper wire between HFC terminal and POWER-TO-FAN terminal at LFC relay wiring harness connector (Black/Red to Blue/Yellow wires). Turn ignition on. If fan operates, remove jumper and go to step 16). If fan does not operate, remove jumper wire and go to next step.

14) Check LFC POWER-TO-FAN Circuit Continuity Turn ignition off. Disconnect LFC relay and cooling fan. Measure resistance between POWER-TO-FAN terminal at LFC wiring harness connector and POWER-TO-FAN input terminal at cooling fan wiring harness connector. If resistance is less than 5 ohms, go to step 15). If resistance is 5 ohms or more, repair open circuit. Reconnect all components and check system operation.

15) Check Cooling Fan Ground Circuit Turn ignition off. Leave LFC relay and cooling fan disconnected. Measure resistance between GND terminal at cooling fan vehicle wiring harness connector and negative battery terminal. If resistance is less than 5 ohms, replace cooling fan. Reconnect all components and check system operation. If resistance is 5 ohms or more, repair open circuit. Reconnect all components and check system operation.

16) Check Circuits From HFC Relays To Fan Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Install a jumper wire between test pins No. 40 and 31 at breakout box. Turn ignition on. If fan runs at high speed, replace LFC relay and check system operation. If fan does not run at high speed, remove jumper wire and go to next step.

17) Check HFC Power-To-Fan Voltage At Fan Turn ignition off. Leave LFC relay disconnected. Disconnect cooling fan connector. Install a jumper wire between test pins No. 31 and 40 at breakout box. Turn ignition on. Measure voltage between HFC POWER-TO-FAN circuit at cooling fan vehicle wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, replace cooling fan and check system operation. If voltage is 10.5 volts or less, remove jumper wire and go to next step.

18) Check HFC POWER-TO-FAN Circuit Continuity Turn ignition off. Leave PCM, cooling fan, HFC and LFC relays disconnected. Measure resistance between HFC POWER-TO-FAN terminal at HFC relay vehicle wiring harness connector and HFC POWER-TO-FAN terminal at cooling fan vehicle wiring harness connector. If resistance is less than 5 ohms, replace HFC relay and check system operation. If resistance is 5 ohms or more, repair open circuit and check system operation.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 18) to step 26). No test procedures have been omitted.

26) Low-Speed (LFC) Or High-Speed (HFC) Cooling Fan Always On, Check For Relay Always Closed - Turn ignition off. Disconnect LFC relay. Turn ignition on. If fan continues to run, go to next step. If fan does not continue to run, replace LFC relay and check system operation.

27) Check HFC Relay Turn ignition off. Disconnect HFC relay. Turn ignition on. If fan continues to run, go to next step. If fan does not continue to run, go to step 30) (A/C equipped with R134a refrigerant) or replace HFC relay and check system operation (all others).

28) Check LFC POWER-TO-FAN Circuit For Short to Power Turn ignition off. Leave cooling fan, LFC and HFC relays disconnected. Turn ignition on. Measure voltage between LFC POWER-TO-FAN terminal cooling fan vehicle wiring harness connector and negative battery terminal. If voltage is more than 1.0 volt, repair short to power in LFC POWER-TO-FAN circuit. Reconnect all components and check system operation. If voltage is 1.0 volt or less, repair short to power in HFC POWER-TO-FAN circuit. Reconnect all components and check system operation.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 28) to step 30). No test procedures have been omitted.

30) Check A/C Pressure Switch (ACPSW) Operation Turn ignition off. Leave LFC relay disconnected. Reconnect HFC relays. Disconnect ACPSW connector. Start engine. If fan runs, go to next step. If fan does not run, check ACPSW. Replace switch as necessary.

Note. ACPSW controls operation of both A/C clutch and engine cooling fan. Contacts for cooling fan portion of ACPSW are normally open. When high side pressure reaches 325 psi (22.9 kg/cm 2 ), switch contacts close. For more information, see appropriate AIR CONDITIONING & HEAT article.

31) Check PCM Turn ignition off. Disconnect 60-pin PCM connector. Turn ignition on. If fan does not run, go to next step. If fan runs, turn ignition off and replace HFC relay(s). Reconnect all components and check system operation.

32) Check ACPSW For Short To Ground Turn ignition off. Leave PCM and ACPSW disconnected. Measure resistance between ACPSW terminal at ACPSW vehicle wiring harness connector and negative battery terminal. If resistance is more than 10,000 ohms, replace PCM. Reconnect all components and check system operation. If resistance is 10,000 ohms or less, repair short to ground in ACPSW circuit. Reconnect all components and check system operation.

Perform this test when instructed by QUICK TEST or if directed by CIRCUIT TEST TA. To prevent replacing good components, check the following non-EEC components and systems

1. Refrigerant charge.
2. Low ambient temperature (less than 45°F). This test is only intended to diagnose
3. Wiring harness circuits (WAC, VPWR, GND, POWER-TO-CLUTCH and ACD).
4. WAC relay.
5. Faulty PCM.

WOT A/C Cut-Out Circuit (KM1). Scheme 24

TEST PIN NO. 10 (ACD) WIRE COLOR IDENTIFICATION

TEST PIN NO. 54 (WAC) WIRE COLOR IDENTIFICATION

Note. A/C switch is also referred to as A/C demand switch in this circuit test.

1) Low/No Voltage To A/C Clutch Check all A/C-related fuses in fuse panel before proceeding with this test.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 60). No test procedures have been omitted.

60) Code 559: Check Power To A/C Relay Code 559 indicates A/C relay input circuit fault. Possible causes are as follows

1. Open or shorted circuit.
2. Damaged A/C relay.
3. Damaged PCM.

Turn ignition off. Disconnect A/C relay. Turn ignition on. Measure voltage between IGN RUN terminal at A/C relay wiring harness connector and chassis ground. If voltage is 10.5 volts or less, repair open circuit and repeat QUICK TEST. If voltage is more than 10.5 volts, go to next step.

Identifying A/C Relay Wiring Harness Connector Terminals (KM2). Scheme 25

61) Check A/C Relay Turn ignition off. Leave A/C relay disconnected. Measure resistance between IGN RUN and ACON terminal at A/C relay. Resistance should be 50-100 ohms. Also, measure resistance between ACON and the following A/C relay terminals; B(+), POWER-TO-CLUTCH and ground. Resistance should be more than 10,000 ohms. If resistance is not as specified, replace A/C relay. Reconnect all components and repeat QUICK TEST. If resistance is as specified, go to next step.

Identifying A/C Relay Terminals (KM3). Scheme 26

62) Check ACON Circuit For Short To Power Turn ignition off. Leave A/C relay disconnected. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 54 and chassis ground. If voltage is 1.0 volt or more, repair short to power. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage is less than 1.0 volt, go to next step.

63) Check ACON Circuit For Short To Ground Leave ignition off and A/C relay disconnected. Measure resistance between test pin No. 54 and chassis ground. If resistance is 10,000 ohms or less, repair short circuit to ground. If resistance is more than 10,000 ohms, go to next step.

64) Check ACON Circuit Continuity Leave ignition off and A/C relay disconnected. Measure resistance between test pin No. 54 and ACON terminal at A/C relay wiring harness connector. If resistance is less than 5 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 64) to step 70). No test procedures have been omitted.

70) Code 539: Check A/C Input Code 539 indicates A/C demand input to PCM was low, indicating A/C on, during KOEO SELF-TEST. Verify A/C is off. If A/C was on, repeat KOEO SELF-TEST. If Code 539 is repeated, turn ignition off. Disconnect low pressure switch. Measure resistance between chassis ground and A/C demand switch (White wire) side of low pressure switch wiring harness connector. If resistance is 10,000 ohms or less, check for defective A/C demand switch. If switch is okay, repair short to ground. Reconnect all components and check system operation. If resistance is more than 10,000 ohms, go to next step.

71) Check Low Pressure Switch Turn ignition off. Leave low pressure switch disconnected. Measure resistance between each terminal of switch and chassis ground. If either resistance is 10,000 ohms or less, replace switch and check system operation. If each resistance is more than 10,000 ohms, go to next step.

72) Check PCM-To-Low Pressure Switch Circuit For Short To Ground Leave ignition off and low pressure switch disconnected. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Measure resistance between chassis ground and PCM side of low pressure switch wiring harness connector. If resistance is 10,000 ohms or less, repair short circuit to ground. Reconnect all components and check system operation. If resistance is more than 10,000 ohms, replace PCM. Reconnect all components and check system operation.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 72) to step 80). No test procedures have been omitted.

80) A/C Always On: Check For Short To Power Perform KOEO SELF-TEST. If any code(s) is present, service as necessary. If no code(s) is present, turn ignition off. Disconnect A/C relay and A/C clutch. Turn ignition on. Measure voltage between power side of A/C clutch wiring harness connector and negative battery terminal. If voltage is 1.0 volt or more, repair short to power. Reconnect all components and check system operation. If voltage is less than 1.0 volt, go to next step.

81) Check A/C Relay Turn ignition off. Leave A/C relay disconnected. Measure resistance between POWER-TO-CLUTCH and terminals B(+) and IGN RUN at A/C relay. If both readings are more than 10,000 ohms, EEC system is okay. Check for fault in A/C system. If any reading is 10,000 ohms or less, replace A/C relay. Reconnect all components and check system operation.

Perform this test when instructed during QUICK TEST. Use this test only to diagnose

1. FPRC solenoid.
2. Wiring harness circuits (FPRC and VPWR).
3. Faulty Powertrain Control Module (PCM).

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

1. Fuel pressure regulator.
2. Engine not obtaining correct operating temperature.
3. Vacuum hoses leaking or misrouted.
4. Excessive internal engine wear or damage.

FPRC Solenoid Circuit (KN1). Scheme 27

TEST PIN NO. 32 (FPRC) WIRE COLOR IDENTIFICATION

1) Code 554: Enter OUTPUT STATE CHECK Code 554 indicates fault in FPRC circuit. Possible causes are

1. Faulty FRPC solenoid.
2. Vacuum hoses leaking or misrouted.
3. Open or shorted circuit.
4. Faulty PCM.

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 Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. (Scheme 6) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate PCM has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase, depress throttle to WOT and release. If voltage increases, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase, leave test equipment connected and go to CIRCUIT TEST QC.

Identifying DLC Terminals (KN2). Scheme 28

2) Check FPRC Solenoid Operation Disconnect FPRC solenoid. Turn ignition on. Connect DVOM positive lead to VPWR terminal and negative lead to FPRC terminal at FPRC solenoid wiring harness connector. Observe DVOM while depressing and releasing throttle 3-5 times. If FPRC solenoid output voltage varies 1.0 volt or less, go to step 7). If FPRC solenoid output voltage varies more than 1.0 volt, go to next step.

3) Check Vacuum Hose Turn ignition off. Disconnect vacuum hose between manifold vacuum source and FPRC solenoid input port. Inspect vacuum hose for kinks, blockage and cracks. Replace hose as necessary. Repeat QUICK TEST. If hose is okay, go to next step.

4) Check FPRC Vacuum Signal Turn ignition off. Using a vacuum tee, connect vacuum gauge between manifold vacuum source and FPRC solenoid input port. Start engine and observe vacuum gauge. If vacuum is present, remove vacuum gauge and go to next step. If vacuum is not present, check engine mechanical condition (valves, vacuum leaks, timing, EGR valve, etc.).

5) Check Vacuum Hose Turn ignition off. Disconnect vacuum hose between FPRC solenoid output port and fuel pressure regulator. Inspect vacuum hose for kinks, cracks and blockage. Replace hose as necessary. Repeat QUICK TEST. If hose is okay, reconnect hose and go to next step.

6) Check FPRC Solenoid Operation Turn ignition off. Install vacuum gauge between FPRC solenoid output port and fuel pressure regulator. Perform road test as follows

1. Warm engine to normal operating temperature.
2. Observe vacuum gauge and accelerate heavily to 40 MPH.
3. Observe vacuum gauge and decelerate to a steady cruise below 20 MPH.

Vacuum gauge should indicate a low vacuum (FPRC solenoid closed) during heavy acceleration and a higher vacuum (FPRC solenoid open) during steady cruise if FPRC solenoid is functioning properly. Repeat test as necessary to confirm test results. If vacuum signal is as specified, remove vacuum gauge and check for fuel system malfunction. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. If vacuum signal is not as specified, replace FPRC solenoid. Repeat QUICK TEST.

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

8) Check Continuity Of FPRC Circuit Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect FPRC solenoid wiring harness connector. Measure resistance between test pin No. 32 and FPRC terminal at solenoid wiring harness connector. If resistance is 5 ohms or more, repair open circuit. Repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

9) Check FPRC Circuit For Short Leave ignition off and FPRC solenoid disconnected. Measure resistance between test pin No. 32 and test pins No. 37 and 57. Also, measure resistance between test pin No. 32 and test No. 40, 46 and 60. If any resistance is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If each resistance is more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST.

To prevent replacing good components, be aware the 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. Engine did not go over 2000 RPM during WOT. This test is only intended to diagnose
3. Throttle movement (minimum 3/4 throttle).
4. 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.

Code 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; Diagnostic Test Code (DTC) output begins.

Ensure vehicle speed reached 2000 RPM during WOT. If Code 538 is present, replace PCM. Repeat QUICK TEST. If Code 538 is not present, vehicle has passed dynamic response test. Service other codes if necessary.

The IDM is an input signal to the PCM that verifies spark plug fire based on ignition coil primary discharge. IDM signal consists of a single pulse for each engine RPM. No IDM pulse indicates secondary ignition misfire.

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 SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. To prevent replacing good components, be aware the following non-EEC related areas may be cause of problem

1. Ignition Control Module (ICM).
2. Ignition coil.
3. Spark plugs and/or wires.
4. Distributor.
5. Secondary ignition short to ground. This test is intended to diagnose
6. IDM circuit.
7. Faulty PCM.

IDM Circuit Schematic (NA1). Scheme 29

TEST PIN NO. 4 (IDM) WIRE COLOR IDENTIFICATION

TEST PIN NO. 36 (SPOUT) WIRE COLOR IDENTIFICATION

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

1. Loose wires or connectors.
2. Arcing secondary ignition components.
3. On-board transmitter equipment (2-way radio).

If any of the above possible causes are present, repair as necessary. Clear code, and repeat QUICK TEST. If problem is not found, go to next step. If vehicle does not start, go to CIRCUIT TEST AA.

2) Continuous Memory Code 212: Check IDM Circuit Continuity Continuous Memory Code 212 indicates loss of IDM input to PCM. Possible causes for this fault are

1. Open or shorted circuit in wiring harness.
2. Faulty ICM.
3. Faulty PCM.

If vehicle is a no-start, see IGNITION SYSTEMS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. If vehicle starts, go to next step.

3) Check IDM Circuit Continuity Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect ICM. Measure resistance between test pin No. 4 at breakout box and IDM terminal at ICM wiring harness 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.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 5). No test procedures have been omitted.

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

6) Check IDM Circuit For Short To PIP & VREF Turn ignition off. Leave PCM and ICM disconnected. Remove scan tool (if applicable). For shorts to PIP, measure resistance between test pins No. 4 and No. 56 at breakout box. For shorts to VREF, measure resistance between test pins No. 4 and No. 26 at breakout box. If each resistance is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If each resistance is more than 10,000 ohms, go to next step.

During this test, a short to SIG RTN (pin No. 46) may be indicated along with an actual short to PWR GND when 4-wire HO2S is connected to vehicle wiring harness.

7) Check IDM Circuit For Short To Ground Turn ignition off. Leave ICM and PCM disconnected. Measure resistance between test pin No. 4 and test pins No. 20, 40, 46 and 60 at breakout box. If each resistance is more than 10,000 ohms, go to next step. If any resistance is 10,000 ohms or less, repair short to ground in IDM circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

8) Check ICM Turn ignition off. Connect PCM to breakout box. Reconnect ICM to wiring harness connector. Connect DVOM between test pins No. 4 and 16 at breakout box. Start engine. Observe DVOM for voltage surge while lightly tapping on ICM to simulate road shock. Wiggle all ICM sensor wiring and harness connectors. If fault (voltage surge) is not indicated, go to next step. If fault (voltage surge) is indicated, disconnect and inspect wiring harness connectors and terminals for damage. Repair as necessary. If connectors and terminals are okay, check ignition system. See SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

9) Check PCM & Harness Connectors Ensure engine is still running and DVOM is still connected between test pins No. 4 and 16 at breakout box. While observing DVOM, wiggle and bend wiring harness, a small section at a time, from ICM and CMP sensor (if equipped) to cowl. Also, check harness from cowl to PCM. If fault is indicated, isolate fault and repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST. If no fault is found, go to next step.

10) Check PCM & Harness Connectors Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. If connector is damaged, repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST. If connector is okay, go to next step.

11) Check PCM For Short To Power Turn ignition off. Connect PCM to breakout box. Disconnect ICM wiring harness connector. 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 and 60 at breakout box. If any reading is more than 10.5 volts, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST. If both readings are 10.5 volts or less, go to next step.

12) Check PCM For Short To Ground Turn ignition off. Leave PCM connected to breakout box. Disconnect ICM and CMP. Measure resistance between test pin No. 4 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check ignition system. See the SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section. If any reading is 10,000 ohms or less, replace PCM. Remove breakout box, reconnect all components, 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. Powertrain Control Module (PCM).

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

1. Basic engine condition (compression, valve timing, etc.).
2. Distributor.
3. Ignition Control Module (ICM).

Spark Timing Check Ckt. (PA1 - 2.0L W/ Dist. Mounted ICM). Scheme 30

TEST PIN NO. 36 (SPOUT) WIRE COLOR IDENTIFICATION

1) Check For Power To PCM Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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 reading is 10.5 volts or less volts, go to CIRCUIT TEST B. If both voltage readings are more than 10.5 volts, go to next step.

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

3) Check SPOUT Circuit For Short To B+ Turn ignition off. Leave PCM and ICM disconnected. Turn ignition on. Measure voltage between test pin No. 36 and test pins No 40 or 60. If voltage is more than 10.5 volts, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage is 10.5 volts or less, go to next step.

4) Check SPOUT Circuit For Short To PIP, VREF & Ground Turn ignition off. Leave PCM and ICM disconnected. To check for shorts to VREF, use DVOM to measure resistance between test pins No. 26 and 36 at breakout box. To check for shorts to PIP, measure resistance between test pins No. 36 and 56 at breakout box. To check for shorts to ground, measure resistance between test pin No. 36 and test pins 16, 20, 40, 46 and 60 at breakout box. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are more than 10,000 ohms, EEC system is okay. Check ignition system. See IGNITION SYSTEMS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

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.

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

1. Powertrain Control Module (PCM).
2. EEC power relay.
3. Wiring harness circuits (HO2S, SIG RTN, STO, STI, VPWR and VREF).

No Codes/Codes Not Listed Circuits (QA1). Scheme 31

WIRE COLOR IDENTIFICATION

1) Check VREF Voltage At Data Link Connector (DLC) Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Turn ignition on. Measure voltage between test pin No. 26 at breakout box and SIG RTN terminal at DLC. If reading is 4-6 volts, go to step 3). If reading is not 4-6 volts, go to next step.

2) Check SIG RTN Circuit Continuity Turn ignition off. Disconnect PCM from breakout box. Measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at DLC. If reading 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 PCM 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. Remove breakout box, reconnect all components, and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.

4) Check STO Circuit Continuity Leave ignition off and PCM disconnected. Measure resistance between test pin No. 17 at breakout box and STO terminal at DLC. If resistance is less than 5 ohms, go to step 5). If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

Diagnostic Aid

A HO2S short to power could prevent EEC system from entering self-diagnostics.

5) Check HO2S Signal For Short To Power Leave PCM disconnected. Turn ignition on. Measure voltage between test pin No. 40 or 60 and HO2S SIGNAL test pin No. 44 at breakout box. For HO2S circuit schematics, see 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 HO2S Sensor Turn ignition off. Leave PCM disconnected. Disconnect right/rear HO2S sensor connector. Turn ignition on. Measure voltage between HO2S SIGNAL test pin No. 44 and test pin No. 40 or 60 at breakout box. If any reading is more than 2 volts, repair short to power in HO2S SIGNAL circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage is 2 volts or less, replace HO2S sensor. Remove breakout box, reconnect all components, and repeat QUICK TEST.

7) Check STO Circuit For Short To Ground Turn ignition off. Leave PCM disconnected. Measure resistance between STO at DLC and engine ground. If reading is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair STO or MIL circuit for short to ground. Remove breakout box, reconnect all components, and repeat QUICK TEST.

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

9) Check VPWR Circuit For Short To Power Turn ignition off. Leave PCM disconnected. Disconnect EEC power relay. Connect DVOM to test pin No. 37 or 57 and test pin No. 40 or 60 at breakout box. If voltage is more than 1.0 volt, repair VPWR circuit short to power. Remove breakout box, reconnect all components, and repeat QUICK TEST. If voltage is 1.0 volt or less, replace EEC power relay. Remove breakout box, reconnect all components, and repeat QUICK TEST.

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

1. Faulty Powertrain Control Module (PCM).
2. KAPWR wiring harness circuits.

KAPWR Circuit Schematic (QB1). Scheme 32

TEST PIN NO. 1 (KAPWR) WIRE COLOR IDENTIFICATION

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

1) Continuous Memory Code 512: Check KAPWR Circuit Voltage Code 512 indicates PCM power interruption in Keep-Alive Memory (KAM). Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure voltage between test pin No. 1 and test pin No. 40 or 60 at breakout box. Observe DVOM while wiggling small sections of EEC wiring harness from PCM to dash. If voltage is less than 10.5 volts, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.

2) Inspect Wiring Harness Routing Ensure EEC wiring is not routed close to ignition components and secondary ignition wires. If necessary, reroute EEC wiring. Clear codes, and wait 5 minutes. Repeat KOEO SELF-TEST. If Continuous Memory Code 512 is not repeated, service other codes as necessary. If no other codes are present, testing is complete. If Continuous Memory Code 512 is still present, replace PCM and repeat QUICK TEST.

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

1. Throttle plate linkage.

1) Check For Codes 23, 53, 63, 121, 122 & 123 Disconnect cruise control servo wiring harness connector (if equipped). Perform KOEO SELF-TEST. If Code 23, 53, 63, 121, 122 or 123 is present, go to appropriate CIRCUIT TEST. See DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS, and service codes as necessary. If Code 111 (pass code) is displayed, go to next step. 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 (TP) sensor 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. This test is intended to diagnose

1. IAC system.
2. EGR system.

1) IAC 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 3). If engine starts and idles smoothly, go to next step.

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

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 2) to step 8). No test procedures have been omitted.

8) Check EGR Vacuum Disconnect and plug vacuum line at EGR valve. Attempt to start engine. If vehicle could not start previously and still does not start or if vehicle driveability fault is still present, go to next step. If vehicle did not start previously but starts now or if driveability symptoms are eliminated, go to CIRCUIT TEST DD, step 31).

9) Check EGR Valve Inspect EGR valve for leaks. If valve is fully closed, go to CIRCUIT TEST H. 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. To prevent replacing good components, be aware the following non-EEC areas may be at fault

1. Engine condition (compression, cam timing, valves, etc.).
2. Charging system or battery.
3. Transmission linkage, internal components or cooling.

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

1. Wiring harness circuits TCC, 3-2T/CCS, EPC, SS1, SS2, SS3, SIG RTN, EPC PWR and VPWR.
2. Faulty Powertrain Control Module (PCM).

CIRCUIT TEST TC ACRONYMS

CD4E Solenoid Circuits (TC1). Scheme 33

CD4E DIAGNOSTIC TROUBLE CODE IDENTIFICATION

1) OUTPUT STATE CHECK Codes 621, 622, 641 and 652 indicates shift solenoid did not respond to PCM command. Possible causes for these faults are

1. Faulty solenoid assembly.
2. Circuit open or grounded.
3. Faulty Powertrain Control Module (PCM).

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 Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between SIG RTN terminal and STI terminal at DLC. (Scheme 31) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate PCM has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase, depress throttle to WOT and release. If STO voltage goes high, go to next step. If STO voltage does not go high, leave test equipment connected and go to CIRCUIT TEST QC.

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 wiring harness connector VPWR terminal. Connect negative test lead to appropriate shift solenoid terminal at transmission wiring harness connector. Turn ignition on. 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, remove jumper wire between SIG RTN terminal and STI terminal at DLC. Go to next step.

3) Check Solenoid & VPWR Circuit Continuity Turn ignition off. Leave transmission wiring harness disconnected. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between suspect signal output terminal at transmission wiring harness connector terminal and corresponding test terminal at breakout box. See appropriate wiring schematic at beginning of this circuit test. Also, measure resistance between breakout box test pins No. 37 and 57 and VPWR terminal at transmission wiring harness connector. If each resistance is less than 5 ohms, go to next step. If any resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

4) Check Solenoid Circuit For Short To Power Or Ground Leave ignition off and PCM disconnected. Leave transmission wiring harness disconnected. Measure resistance between PCM output signal test pin and test pins No. 37 and 57 at breakout box. Also, measure resistance between PCM output signal test pin and pins No. 40, 46 and 60 at breakout box and chassis ground. Measure resistance between PCM output signal test pin and chassis ground. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are 10,000 ohms or more, check solenoids. If solenoids are okay, replace PCM. Remove breakout box, reconnect all components, 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 624: Check VPWR To Solenoid Code 624 indicates failure of EPC circuit. Possible causes for faults are

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

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

11) Check Solenoid Signal & VPWR Circuit Continuity Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between VPWR/EPC PWR terminal at transmission wiring harness connector breakout box test pins No. 37 and 57. Also, measure resistance between test pin No. 38 at breakout box and EPC terminal at transmission wiring harness connector. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.

12) Check Circuit For Short To Power Or Ground Leave ignition off and PCM disconnected. Leave transmission wiring harness connector disconnected. Measure resistance between test pins No. 37 and 57 and suspect solenoid test pin at breakout box. Also, measure resistance between test pins No. 40, 46 and 60 and suspect solenoid test pin at breakout box. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST. If all readings are more than 10,000, check solenoids. If solenoids are okay, replace PCM. Remove breakout box, reconnect all components, 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) Code 621, 622, 641 Or 643: Check Solenoid Resistance KOEO Code 621 (SS1), 622 (SS2), 641 (SS3) or 643 (TCC) indicate failure in shift solenoid circuit. Possible causes for these faults are

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

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 13-27 ohms, go to next step. If resistance is not 13-27 ohms, go to step 25).

21) Check Shift Solenoid For Short To Power Leave ignition off and transmission wiring harness connector disconnected. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Turn ignition on. Measure voltage between suspect shift solenoid at transmission wiring harness connector and chassis ground. If voltage is 0.5 volt or more, repair short to power and repeat QUICK TEST. If voltage is less than 0.5 volt, go to next step.

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. Also, measure resistance between suspect shift solenoid and other circuits at transmission wiring harness connector. If any reading is 10,000 ohms or less, repair short circuit. Reconnect all components and repeat QUICK TEST. If all readings are more than 10,000 ohms, go to next step.

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

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

25) Check Transmission Wiring Leave ignition off. Check transmission wiring harness circuits and connectors breaks or corrosion in insulation. Check for open or grounded circuits. Repair or replace as necessary. If connectors and circuits are okay, replace suspect solenoid and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 25) 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 (TCC) 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 PCM and transmission. Repair or replace wiring as necessary. If circuits are okay, go to next step.

31) Check For Intermittent Short Or Open Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Connect test light between test pin No. 37 and suspect shift solenoid test pin at breakout box. See IDENTIFYING SHIFT SOLENOID TEST CIRCUITS table. Test light should be at partial brightness. Observe test light while wiggling and bending shift solenoid circuit between transmission and PCM. An open or short to power will be indicated by light going off. A short to ground will be indicated by light getting brighter. Repeat procedure for all solenoids. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to next step.

IDENTIFYING SHIFT SOLENOID TEST CIRCUITS

32) Check For Intermittent Short To Ground Leave ignition off and PCM disconnected. Disconnect transmission wiring harness connector. Turn ignition on. Connect test light between test pin No. 37 and suspect shift solenoid test pin at breakout box. Test light should be off. Observe test light while wiggling and bending shift solenoid circuit between transmission and PCM. 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. Remove breakout box, reconnect all components, and repeat QUICK TEST. If no fault is indicated, problem is intermittent and cannot be duplicated at this time.