Engine Control System - System Testing & Engine Component Tests: Other Saturn SL II

AIR INDUCTION SYSTEMS

Note. Manufacturer does not provide testing procedures for many individual systems and components. For system and component testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Boost Control System Check (3.8L VIN 1)

1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
2. Disconnect boost control solenoid harness connector located at left rear of engine, near valve cover. Turn ignition on. Using a test light connected to ground, probe ignition feed circuit at boost control solenoid harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
3. Connect test light between boost control solenoid harness connector terminals. If test light illuminates, go to step 14 . If test light does not illuminate, go to next step.
4. Connect scan tool to Data Link connector (DLC). Using scan tool, select OUTPUT TESTS, and then BOOST SOL. Observe test light while commanding boost control solenoid output ON using scan tool. If test light illuminates when solenoid output is commanded ON, go to next step. If test light does not illuminate when solenoid output is commanded ON, go to step 16 .
5. Reconnect boost control solenoid harness connector. Disconnect boost vacuum hose between solenoid and by-pass valve actuator located above boost control solenoid. Connect vacuum gauge to boost control solenoid. Place transmission in Park, start engine and allow engine to idle. Observe vacuum gauge reading. If vacuum does not exist, go to next step. If vacuum exists, go to step 17 .
6. Using scan tool, command boost control solenoid OFF. Observe vacuum gauge reading. If vacuum is greater than 15 in. Hg, go to next step. If vacuum is less than 15 in. Hg, go to step 10 .
7. Check for restriction in boost vacuum hose between boost control solenoid and by-pass valve actuator. If restriction does not exist, go to next step. If restriction exists, repair as necessary and go to step 21 .
8. Reconnect boost vacuum hose between boost control solenoid and by-pass valve actuator. Connect vacuum gauge to read inlet vacuum signal to by-pass valve actuator. Place transmission in Park, start engine and allow engine to idle. Observe vacuum gauge reading. If vacuum is greater than 15 in. Hg, go to «DIAGNOSTIC AIDS»(ref-180-S41668946272000030800000) . If vacuum is less than 15 in. Hg, go to next step.
9. Repair restriction in inlet vacuum signal hose to by-pass valve actuator or blocked inlet vacuum source. After repairs, go to step 21 .
10. Check for restriction in vacuum hose to boost control solenoid. If restriction does not exist, go to step 18 . If restriction exists, repair as necessary and go to step 21 .
11. Check boost control solenoid ignition feed circuit fuse. If fuse is blown, go to next step. If fuse is okay, go to step 13 .
12. Locate and repair short to ground in ignition feed circuit to boost control solenoid. After repairs, go to step 21 .
13. Locate and repair open in ignition feed circuit to boost control solenoid. After repairs, go to step 21 .
14. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Connect test light between boost control solenoid harness connector terminals. If test light illuminates, go to next step. If test light does not illuminate, go to step 20 .
15. Locate and repair short to ground in boost control solenoid control circuit. After repairs, go to step 21 .
16. Turn ignition off. Disconnect PCM harness connector. Turn ignition on. Check boost control solenoid control circuit for an open or short to voltage. If open or short exists, repair as necessary and go to step 21 . If open or short does not exist, go to step 19 .
17. Check for poor terminal connections at boost control solenoid. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 21 .
18. Replace boost control solenoid. After repairs, go to step 21 .
19. Check boost control solenoid control circuit for a poor terminal connection at PCM. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 21 .
20. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.
21. Disconnect inlet vacuum signal hose from by-pass valve actuator. Start engine and allow engine to idle. Using scan tool, select OUTPUT TESTS, and then BOOST SOL. Observe MAP sensor reading on scan tool while cycling boost control solenoid ON and OFF. If MAP sensor value decreases while boost control solenoid is commanded ON, and increases while boost solenoid is commanded OFF, system is operating properly. Reconnect inlet vacuum signal hose to by-pass valve actuator. If MAP sensor value is not as specified, go to step 2 .

PCM POWER & GROUND CHECK

Note. To identify circuits referenced in the following ground and power tests, see appropriate wiring diagram in WIRING DIAGRAMS article.

Ground Circuits

1. Using an ohmmeter, check for continuity to ground at PCM ground terminals. See «POWERTRAIN CONTROL MODULE (PCM) CONNECTOR TERMINAL IDENTIFICATION»(ref-180-S38192318482000030800000). (Схема №1) Resistance should be zero ohms. If resistance is not zero ohms, repair open in ground circuit.
2. Connect negative lead of voltmeter to a known good ground. Backprobe positive lead of voltmeter to each PCM ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, short to voltage, corrosion or loose connection in ground circuit.

Power Circuits

1. Using a voltmeter, check for battery voltage between PCM continuous power terminal(s) and ground. See «POWERTRAIN CONTROL MODULE (PCM) CONNECTOR TERMINAL IDENTIFICATION»(ref-180-S38192318482000030800000). (Схема №1) If battery voltage is not present, check for blown fuse or open fusible link. If fuse or fusible link is okay, check for open in circuit between PCM continuous power terminal and power source.
2. Turn ignition switch to RUN position. Using a voltmeter, check for battery voltage between PCM ignition power terminals and ground. If battery voltage is not present, check IGN fuse. If fuse is okay, check for an open in circuit between battery and ignition switch, and between ignition switch and PCM ignition power terminal. If circuits are okay, check for a defective ignition switch.
3. Connect voltmeter between ground and PCM starter (crank) signal terminal. On vehicles with manual transmission/transaxle, depress clutch pedal. On vehicles with automatic transmission/transaxle, place gear shift lever in Park. On all vehicles, turn ignition switch to START position. Battery voltage should be present only when ignition switch is in START position.
4. If voltage is not present, check CRANK fuse or fusible link between ignition switch and PCM starter (crank) signal terminal. If fuse or fusible link is okay, check for an open in circuit between ignition switch and PCM starter (crank) signal terminal, or check for a defective ignition switch.

ENGINE SENSORS & SWITCHES

Note. For additional sensor testing specifications, see appropriate SENSOR OPERATING RANGE CHARTS article.

Manufacturer does not provide testing procedures for many individual systems and components. For sensor and switch testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Engine Coolant Level Switch Diagnosis (2.2L & 2.4L)

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Turn ignition on, with engine off. Install scan tool and retrieve DTCs. If no DTCs are set, go to next step. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
3. Turn ignition off and wait 10 seconds. Turn ignition on, with engine off. If coolant level indicator illuminates for about 3 seconds, and then turns off and remains off, go to next step. If coolant level indicator does not illuminate for about 3 seconds, and then turn off and remain off, go to step 5 .
4. Drain coolant from surge tank. If coolant level indicator does not illuminate, go to step 6 . If coolant level indicator illuminates, go to step 20 .
5. Check coolant level in surge tank. If coolant level is not okay, go to step 8 . If coolant level is okay, go to step 7 .
6. Disconnect engine coolant level switch harness connector. Using a test light connected to battery voltage, probe engine coolant level switch ground circuit (Black/White wire) at engine coolant level switch harness connector. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 10 .
7. Disconnect engine coolant level switch harness connector. If coolant level indicator does not illuminate, go to step 17 . If coolant level indicator illuminates, go to step 11 .
8. Fill surge tank and go to step 2 .
9. Using DVOM connected to ground, probe engine coolant level switch signal circuit (Yellow/Black wire) at engine coolant level switch harness connector. If battery voltage exists, go to step 12 . If battery voltage does not exist, go to step 13 .
10. Repair poor connection or open in engine coolant level switch ground circuit (Black/White wire). After repairs, go to step 20 .
11. Using a test light connected to battery voltage, probe engine coolant level switch signal circuit (Yellow/Black wire) at engine coolant level switch harness connector. If test light illuminates, go to step 14 . If test light does not illuminate, go to step 15 .
12. Using a test light connected to ground, probe engine coolant level switch signal circuit (Yellow/Black wire) at engine coolant level switch harness connector. If test light illuminates, go to step 16 . If test light does not illuminate, go to step 17 .
13. Check for poor connection or open in engine coolant level switch signal circuit (Yellow/Black wire). If problem does not exist, go to step 19 . If problem exists, repair as necessary and go to step 20 .
14. Check for short to ground in engine coolant level switch signal circuit (Yellow/Black wire). If problem does not exist, go to step 19 . If problem exists, repair as necessary and go to step 20 .
15. Install scan tool. Using scan tool, observe engine coolant level display. If scan tool displays LOW, go to step 19 . If scan tool does not display LOW, go to step 18 .
16. Check for short to voltage in engine coolant level switch signal circuit (Yellow/Black wire). If problem does not exist, go to step 19 . If problem exists, repair as necessary and go to step 20 .
17. Turn ignition off. Replace engine coolant level switch. After repairs, go to step 20 .
18. Turn ignition off. Replace instrument cluster. After repairs, go to step 20 .
19. Turn ignition off. Check for poor electrical connections at PCM. If connections are okay, replace PCM. After repairs, go to next step.
20. Operate vehicle under conditions which original symptom was noted. If system operates properly, system is okay. If system does not operate properly, go to step 2 .

Engine Coolant Level Switch Diagnosis (3.4L)

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Ensure engine coolant surge tank is full. Add coolant as necessary. Turn ignition off. Disconnect PCM harness connector C2. Using a test light connected to battery voltage, probe engine coolant level switch signal circuit (Yellow/Black wire) at PCM harness connector. If test light does not illuminate, go to next step. If test light illuminates, go to step 6 .
3. Turn ignition off. Reconnect PCM harness connector. Turn ignition on. Raise and support vehicle. Disconnect engine coolant level switch harness connector. Using DVOM, measure voltage between engine coolant switch harness connector terminals. If battery voltage is present, go to step 7 . If battery voltage is not present, go to next step.
4. Using DVOM, measure voltage between engine coolant level switch harness connector signal circuit (Yellow/Black wire) and chassis ground. If battery voltage is present, go to step 8 . If battery voltage is not present, go to next step.
5. Check for an open in engine coolant level switch signal circuit (Yellow/Black wire). If problem does not exist, go to step 10 . If problem exists, repair as necessary and go to step 12 .
6. Check for a short to ground in engine coolant level switch signal circuit (Yellow/Black wire). If problem does not exist, go to step 10 . If problem exists, repair as necessary and go to step 12 .
7. Check for poor terminal connections at engine coolant level switch harness connector. If problem does not exist, go to step 9 . If problem exists, repair as necessary and go to step 12 .
8. Locate and repair open in engine coolant level switch ground circuit. After repairs, go to step 12 .
9. Replace engine coolant level switch. After repairs, go to step 12 .
10. Diagnose instrument panel cluster microprocessor. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 12 .
11. Replace PCM. After repairs, go to next step.
12. Check coolant level indicator for proper operation. If coolant level indicator operates properly, system is okay. If coolant level indicator does not operate properly, go to step 2 .

Engine Coolant Level Switch Diagnosis (4.0L)

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Ensure engine coolant surge tank is full. Add coolant as necessary. Install scan tool and turn ignition on. Using scan tool, observe engine coolant level display. If scan tool displays OK, go to next step. If scan tool does not display OK, go to step 4 .
3. Disconnect engine coolant level switch harness connector. Using scan tool, observe engine coolant level display. If scan tool displays LOW, check for intermittent. Engine coolant level switch shares a common ground with other sensor and switches. An intermittent in shared ground connection(s) may cause low coolant indicator to illuminate with coolant level okay. If coolant level is low and low coolant indicator does not illuminate, check for a binding or stuck closed engine coolant level switch. If scan tool does not display LOW, go to step 7 .
4. Disconnect engine coolant level switch harness connector. Connect a fused jumper wire between engine coolant level switch harness connector terminals. Observe scan tool display. If scan tool displays OK when connector terminals are jumpered and LOW when jumper wire is removed, go to step 8 . If scan tool display is not as specified, go to next step.
5. Using a fused jumper wire, connect engine coolant level input circuit (Light Green wire) to ground. Observe scan tool display. If scan tool displays OK when connector terminal is jumpered and LOW when jumper wire is removed, go to step 13 . If scan tool display is not as specified, go to next step.
6. Turn ignition off. Remove fused jumper wire. Disconnect PCM harness connector C2 . Using DVOM, measure resistance of engine coolant level input circuit (Light Green wire) between PCM connector C2 and engine coolant level switch harness connector. If resistance is 5 ohms or less, go to step 9 . If resistance is greater than 5 ohms, go to step 10 .
7. Check for a short to ground in engine coolant level switch input circuit (Light Green wire). If problem does not exist, go to step 11 . If problem exists, repair as necessary.
8. Check for poor connections at engine coolant level switch. If problem does not exist, go to step 12 . If problem exists, repair as necessary.
9. Check for poor connection at PCM. If problem does not exist, go to step 11 . If problem exists, repair as necessary.
10. Locate and repair open in engine coolant level input circuit.
11. Replace PCM.
12. Replace engine coolant level switch.
13. Locate and repair open in engine coolant level switch ground circuit.

Engine Coolant Level Switch Diagnosis (4.6L)

1. Did you perform the IPC Diagnostic System Check? If so, go to next step. If not, go to «IPC DIAGNOSTIC SYSTEM CHECK»(ref-977-S22008074522000031300000) .
2. Disconnect the coolant level switch. Connect a fused jumper from the harness terminal A to terminal B. Turn the ignition switch to the RUN position. Is the CHECK COOLANT LEVEL message displayed on the DIC? If so, go to step 7 . If not, go to next step.
3. Disconnect the IPC connector C2. Connect a J 39200 from the IPC connector C2 terminal A10 battery positive voltage. Is the Voltage between 10-15 volts? If so, go to step 8 . If not, go to next step.
4. Connect a DMM fused jumper from harness terminal A to ground. Is the voltage between 10-15 volts? If so, go to step 7 . If not, go to next step.
5. Repair the open in CKT 1478. After repairs are complete, go to «IPC DIAGNOSTIC SYSTEM CHECK»(ref-977-S22008074522000031300000) .
6. Repair the open in CKT 650. After repairs are complete, go to «IPC DIAGNOSTIC SYSTEM CHECK»(ref-977-S22008074522000031300000) .
7. Replace the coolant level switch (located in coolant recovery bottle). After repairs are complete, go to «IPC DIAGNOSTIC SYSTEM CHECK»(ref-977-S22008074522000031300000) .
8. Replace the IPC. See «INSTRUMENT PANEL CLUSTER (IPC)»(ref-977-S06768245162000031300000) . After repairs are complete, go to «IPC DIAGNOSTIC SYSTEM CHECK»(ref-977-S22008074522000031300000) .

Engine Oil Level Switch Diagnosis (3.1L, 3.4L & 3.8L)

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Using scan tool, observe engine oil level display. If scan tool does not display OK, go to next step. If scan tool displays OK, check the following: Poor connections at engine oil level switch and PCM. Check for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection. Inspect wiring harness for damage. If harness is okay, disconnect PCM and turn ignition on. Connect DVOM to affected PCM output circuit. Wiggle connectors and wiring harnesses related to PCM output circuit. A change in voltage will indicate location of fault. On 3.1L and 3.8L, if fault in oil level indicator cannot be isolated using engine oil level switch diagnosis, perform PCM controlled warning light diagnosis. See «PCM CONTROLLED WARNING LIGHTS»(ref-180-S23918172502000030800000) under MISCELLANEOUS CONTROLS.
3. Turn ignition off. Disconnect PCM harness connector C2. Using a test light connected to battery voltage, probe engine oil level switch signal circuit (Brown wire) at PCM harness connector. If test light does not illuminate, go to next step. If test light illuminates, go to step 7 .
4. Turn ignition off. Reconnect PCM harness connector. Turn ignition on. Raise and support vehicle. Disconnect engine oil level switch harness connector. Using DVOM, measure voltage between engine oil level switch harness connector terminals. If battery voltage is not present, go to next step. If battery voltage is present, go to step 8 .
5. Using DVOM, measure voltage between engine oil level switch harness connector signal circuit (Brown wire) and chassis ground. If battery voltage is not present, go to next step. If battery voltage is present, go to step 9 .
6. Check for an open in engine oil level switch signal circuit (Brown wire). If problem exists, repair as necessary and go to step 12 . If problem does not exist, check the following: Poor connections at engine oil level switch and PCM. Check for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection. Inspect wiring harness for damage. If harness is okay, disconnect PCM and turn ignition on. Connect DVOM to affected PCM output circuit. Wiggle connectors and wiring harnesses related to PCM output circuit. A change in voltage will indicate location of fault. On 3.1L and 3.8L, if fault in oil level indicator can not be isolated using engine oil level switch diagnosis, perform PCM controlled warning light diagnosis. See «PCM CONTROLLED WARNING LIGHTS»(ref-180-S23918172502000030800000) under MISCELLANEOUS CONTROLS.
7. Check for poor connections at PCM. If problem exists, repair as necessary and go to step 12 . If problem does not exist, go to step 11 .
8. Check for poor connections at engine oil level switch. If problem exists, repair as necessary and go to step 12 . If problem does not exist, go to step 10 .
9. Locate and repair open in engine oil level switch ground circuit (Black/White wire). After repairs, go to step 12 .
10. Replace engine oil level switch. After repairs, go to step 12 .
11. Replace PCM. After repairs, go to next step.
12. Start engine and allow to warm to normal operating temperature. Turn ignition off and allow engine to cool for 15 minutes. Turn ignition on. Using scan tool, observe engine oil level display. If scan tool displays OK, system is okay. If scan tool does not display OK, go to step 3 .

1. Engine Oil Level Switch Diagnosis (3.5L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. If low oil level indicator is illuminated, go to next step. If low oil level indicator is not illuminated, go to step 8 .
3. Install scan tool. Using scan tool, observe engine oil level display. If scan tool displays LOW, go to next step. If scan tool does not display LOW, diagnose instrument cluster.
4. Turn ignition off and allow engine oil to drain back. Check engine oil level. If oil level is okay, system is okay. If oil level is not okay, go to next step.
5. Disconnect engine oil level switch harness connector. Turn ignition on, with engine off. Using DVOM connected to ground, measure voltage of engine oil level switch signal circuit (Brown wire) at engine oil level switch harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 12 .
6. Using DVOM connected to ground, measure resistance of engine oil level switch ground circuit (Black/White wire) at engine oil level switch harness connector. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 14 .
7. Using DVOM, measure resistance between engine oil level switch harness connector terminals. If resistance is 5 ohms or less, go to step 16 . If resistance is greater than 5 ohms, go to step 17 .
8. Turn ignition off. Disconnect engine oil level switch harness connector. Start engine. Using scan tool, observe engine oil level display. If scan tool displays LOW, go to next step. If scan tool does not display LOW, go to step 10 .
9. If low oil level indicator is illuminated, go to step 17 . If low oil level indicator is not illuminated, diagnose instrument cluster.
10. Turn ignition on, with engine off. Using DVOM connected to ground, measure voltage of engine oil level switch signal circuit (Brown wire) at engine oil level switch harness connector. If battery voltage is present, go to step 19 . If battery voltage is not present, go to next step.
11. Turn ignition off. Disconnect PCM harness connector C2. Using DVOM, check for continuity between engine oil level switch signal circuit (Brown wire) at PCM harness connector and chassis ground. If continuity exists, go to step 15 . If continuity does not exist, go to step 19 .
12. Turn ignition off. Disconnect PCM harness connector C2. Using DVOM, check for continuity of engine oil level switch signal circuit (Brown wire). If continuity exists, go to step 18 . If continuity does not exist, go to next step.
13. Repair open or high resistance in engine oil level switch signal circuit.
14. Repair engine oil level switch ground circuit.
15. Repair short to ground in engine oil level switch signal circuit.
16. Check for poor connections at engine oil level switch. If problem exists, repair as necessary. If problem does not exist, go to next step.
17. Replace engine oil level switch.
18. Check for poor connections at PCM. If problem exists, repair as necessary. If problem does not exist, go to next step.
19. Replace PCM.

1. Engine Oil Level Switch Diagnosis (4.0L & 4.6L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Ensure engine oil level is at full mark on dipstick. Install scan tool. Turn ignition on, with engine off. Using scan tool, observe engine oil level display. If scan tool displays OK, go to next step. If scan tool does not display OK, go to step 4 .
3. Start engine and let idle. Increase engine speed to 2300 RPM while monitoring oil level on scan tool. If scan tool displays LOW, no fault is present at this time. If scan tool does not display LOW, go to step 7 .
4. Disconnect engine oil level switch harness connector. Connect a fused jumper wire between engine oil level switch harness connector terminals. Observe scan tool display. If scan tool displays OK, go to step 12 . If scan tool does not display OK, go to next step.
5. Connect a fused jumper wire between engine oil level switch harness connector input circuit (Brown wire) and chassis ground. Observe scan tool display. If scan tool displays OK, go to step 10 . If scan tool does not display OK, go to next step.
6. Turn ignition off. Remove fused jumper wire. Disconnect PCM harness connector C2. Using DVOM, measure resistance in engine oil level input circuit (Brown wire) between PCM connector C2 and engine oil level switch harness connector. If resistance is 5 ohms or less, go to step 14 . If resistance is greater than 5 ohms, go to step 9 .
7. Turn ignition on, with engine off. Disconnect engine oil level switch harness connector. Observe scan tool display. If scan tool displays LOW, go to step 12 . If scan tool does not display LOW, go to next step.
8. Turn ignition off. Disconnect PCM harness connector C2. Using DVOM, measure resistance in engine oil level input circuit (Brown wire) between engine oil level switch harness connector and chassis ground. If resistance is 10,000 ohms or greater, go to step 14 . If resistance is less than 10,000 ohms, go to step 11 .
9. Locate and repair open in engine oil level input circuit.
10. Locate and repair open in engine oil level ground circuit.
11. Locate and repair short to ground in engine oil level switch input circuit.
12. Check for poor connections at engine oil level switch. If problem exists, repair as necessary. If problem does not exist, go to next step.
13. Replace engine oil level switch.
14. Check for poor connections at PCM. If problem exists, repair as necessary. If problem does not exist, go to next step.
15. Replace PCM.

1. Engine Oil Level Switch Diagnosis (5.7L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Turn ignition on, with engine off. Raise and support vehicle. Disconnect engine oil level switch harness connector. Using DVOM, measure voltage between engine oil level switch input circuit (Brown wire) at engine oil level switch harness connector and chassis ground. If battery voltage is present, go to next step. If battery voltage is not present, go to step 4 .
3. Using DVOM, measure voltage between engine oil level switch harness connector terminals. If battery voltage is present, go to step 6 . If battery voltage is not present, go to step 7 .
4. Turn ignition off. Disconnect PCM harness connector C1. Using DVOM, check continuity of engine oil level switch input circuit (Brown wire). If continuity exists, go to next step. If continuity does not exist, go to step 8 .
5. Using a test light connected to battery voltage, probe engine oil level switch input circuit (Brown wire) at engine oil level switch harness connector. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 10 .
6. Check for poor connection at engine oil level switch. If problem does not exist, go to step 12 . If problem exists, repair as necessary.
7. Repair open in engine oil level switch ground circuit.
8. Repair open in engine oil level switch input circuit.
9. Repair short to ground in engine oil level switch input circuit.
10. Check for poor connections at PCM. If problem does not exist, go to next step. If problem exists, repair as necessary.
11. Replace PCM.
12. Replace engine oil level switch.

1. Engine Oil Pressure Switch Diagnosis (3.1L, 3.4L & 3.8L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Turn ignition on, with engine off. Install scan tool and retrieve DTCs. If no DTCs are set, go to next step. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
3. If engine oil pressure indicator illuminates, go to next step. If engine oil pressure indicator does not illuminate, go to step 16 .
4. Check engine oil level. If oil level is okay, go to next step. If oil level is not okay, go to step 11 .
5. Using a manual oil pressure gauge, check engine oil pressure. If engine oil pressure is correct, go to next step. If engine oil pressure is not correct, go to step 12 .
6. Turn ignition off. Disconnect engine oil pressure switch harness connector. Turn ignition on. Using a test light connected to ground, probe engine oil pressure switch input circuit (Tan/Black wire) at engine oil pressure switch harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
7. Using a test light connected to battery voltage, probe engine oil pressure switch ground circuit (Black/White wire) at engine oil pressure switch harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 10 .
8. Check for poor connection at engine oil pressure switch. If problem does not exist, go to step 13 . If problem exists, repair as necessary and go to step 16 .
9. Check for an open or short to ground in engine oil pressure switch input circuit (Tan/Black wire). Also, check for poor connections at PCM. If problem does not exist, go to step 15 . If problem exists, repair as necessary and go to step 16 .
10. Locate and repair open in engine oil pressure switch ground circuit (Black/White wire). Also, on 3.8L, repair poor connections at underhood electrical center pass-through connector. On all models, after repairs, go to step 16 .
11. Determine cause of low engine oil level and repair as necessary. After repairs, go to step 16 .
12. Determine cause of low engine oil pressure and repair as necessary. After repairs, go to step 16 .
13. Check communication circuit for proper operation. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 16 .
14. Replace engine oil pressure switch. After repairs, go to step 16 .
15. Replace PCM. After repairs, go to next step.
16. Check engine oil pressure indicator for proper operation. If engine oil pressure indicator operates properly, system is okay. If engine oil pressure indicator does not operate properly, go to step 2 .

1. Engine Oil Pressure Switch Diagnosis (3.5L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Install scan tool. Turn ignition on, with engine off. Using scan tool, observe engine oil pressure display. If scan tool displays LOW, go to next step. If scan tool does not display LOW, go to step 7 .
3. Start engine. If scan tool displays OK, no fault is present at this time. If scan tool does not display OK, go to next step.
4. Turn ignition off. Check engine oil level. If oil level is okay, go to next step. If oil level is not okay, go to step 11 .
5. Using a manual oil pressure gauge, check engine oil pressure. If engine oil pressure is correct, go to next step. If engine oil pressure is not correct, go to step 12 .
6. Turn ignition off. Disconnect engine oil pressure switch harness connector. Turn ignition on. If scan tool displays OK, go to step 14 . If scan tool does not display OK, go to step 9 .
7. Disconnect engine oil pressure switch harness connector. Connect a jumper wire between engine oil pressure switch harness connector terminals. If scan tool displays LOW, go to step 14 . If scan tool does not display LOW, go to next step.
8. Connect a jumper wire between engine oil pressure switch harness connector input circuit (Tan/Black wire) and chassis ground. If scan tool displays LOW, go to step 10 . If scan tool does not display LOW, go to step 13 .
9. Check for a short to ground in engine oil pressure switch input circuit (Tan/Black wire). If problem does not exist, go to step 15 . If problem exists, repair as necessary and go to step 16 .
10. Repair open in engine oil pressure switch ground circuit (Black/White wire). After repairs, go to step 16 .
11. Determine cause of low engine oil level and repair as necessary. After repairs, go to step 16 .
12. Determine cause of low engine oil pressure and repair as necessary. After repairs, go to step 16 .
13. Check for an open in engine oil pressure switch input circuit (Tan/Black wire). Also, check for poor connections at PCM. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 16 .
14. Replace engine oil pressure switch. After repairs, go to step 16 .
15. Replace PCM. After repairs, go to step 16 .
16. Using scan tool, monitor engine oil pressure with ignition on, engine off. Also, monitor engine oil pressure with engine running. If scan tool displays LOW with ignition on, engine off and OK with engine running, system is okay. If scan tool display is not as specified, go to step 2 .

1. Engine Oil Pressure Switch Diagnosis (4.6L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Turn ignition on, with engine off. Install scan tool. Using scan tool, observe engine oil pressure display. If scan tool displays LOW, go to next step. If scan tool does not display LOW, go to step 6 .
3. Start engine and let idle. Observe scan tool display. If scan tool displays OK, system is okay. If scan tool does not display OK, go to next step.
4. Turn ignition off. Disconnect engine oil pressure switch harness connector. Turn ignition on, with engine off. Observe scan tool display. If scan tool displays OK, go to step 15 . If scan tool does not display OK, go to next step.
5. Using scan tool, record FLUID LIFE INDEXES. Turn ignition off and wait 30 seconds. Disconnect PCM harness connector C2. Using DVOM, measure resistance in engine oil pressure switch input circuit (Tan/Black wire) between PCM harness connector C2 and engine oil pressure switch harness connector. If resistance is 10,000 ohms or greater, go to step 17 . If resistance is less than 10,000 ohms, go to step 11 .
6. Turn ignition off. Disconnect engine oil pressure switch harness connector. Connect a fused jumper wire between engine oil pressure switch harness connector terminals. Turn ignition on, with engine off. Using scan tool, observe engine oil pressure display. If scan tool displays LOW, go to step 15 . If scan tool does not display LOW, go to next step.
7. Connect a fused jumper wire between engine oil level switch harness connector input circuit (Tan/Black wire) and chassis ground. Observe scan tool display. If scan tool displays LOW, go to step 12 . If scan tool does not display LOW, go to next step.
8. Remove jumper wire. Using DVOM, measure voltage at engine oil pressure switch input circuit (Tan/Black wire) at engine oil pressure switch harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 10 .
9. Using scan tool, record FLUID LIFE INDEXES. Turn ignition off and wait 30 seconds. Disconnect PCM harness connector C2. Turn ignition on. Using DVOM, measure voltage at engine oil pressure switch input circuit (Tan/Black wire) at engine oil pressure switch harness connector. If voltage is greater than 0.5 volt, go to step 13 . If voltage is less than 0.5 volts, go to step 17 .
10. Using scan tool, record FLUID LIFE INDEXES. Turn ignition off and wait 30 seconds. Disconnect PCM harness connector C2. Turn ignition on. Using DVOM, measure resistance at engine oil pressure switch input circuit (Tan/Black wire) at engine oil pressure switch harness connector. If resistance is 5 ohms or less, go to step 17 . If resistance is greater than 5 ohms, go to step 14 .
11. Repair short to ground in engine oil pressure switch input circuit.
12. Repair open in engine oil pressure switch ground circuit.
13. Repair short to voltage in engine oil pressure switch input circuit.
14. Repair open in engine oil pressure switch input circuit.
15. Check for poor connection at engine oil pressure switch. If problem does not exist, go to next step. If problem exists, repair as necessary.
16. Replace engine oil pressure switch.
17. Check for poor connections at PCM. If problem does not exist, go to next step. If problem exists, repair as necessary.
18. Replace PCM.

1. Fuel Level Sensor Diagnosis (3.4L & 3.8L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Retrieve instrument panel cluster-related DTCs. If no instrument panel cluster DTCs are set, go to next step. If any instrument panel cluster DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
3. Install scan tool. Turn ignition on. Using scan tool output control function, perform FUEL GAUGE SWEEP TEST. If fuel gauge sweeps through full range, go to next step. If fuel gauge does not sweep through full range, repair fuel gauge. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
4. Turn ignition off. Raise and support vehicle. Disconnect fuel tank pigtail harness from body connector. Connect DVOM between fuel level sensor input circuit (Purple wire) and fuel level sensor ground circuit (Black/White wire) at body connector. Lower vehicle. Turn ignition on. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 6 .
5. Check for an open in fuel level sensor input circuit (Purple wire) or fuel level sensor ground circuit (Black/White wire). Also, check for poor terminal connections at fuel level sensor pigtail harness. If problem does not exist, go to step 10 . If problem exists, repair as necessary and go to step 13 .
6. If voltage is greater than 5 volts in step 4) , go to step 11 . If voltage is less than 5 volts in step 4) , go to next step.
7. Connect DVOM between fuel level sensor input circuit (Purple wire) at body connector and chassis ground. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 9 .
8. Locate and repair open in fuel level sensor ground circuit (Black/White wire). Also, check for poor terminal connections at fuel level sensor pigtail harness. After repairs, go to step 13 .
9. Check for an open or short to ground in fuel level sensor input circuit (Purple wire). If problem does not exist, go to step 11 . If problem exists, repair as necessary and go to step 13 .
10. Replace fuel level sensor. After repairs, go to step 13 .
11. Locate and repair short to voltage in fuel level sensor input circuit (Purple wire). After repairs, go to step 13 .
12. Replace PCM. After repairs, go to next step.
13. Recheck system for proper operation. If system is not operating properly, go to step 2 .

1. Fuel Level Sensor Diagnosis (3.5L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Retrieve instrument panel cluster-related DTCs. If no instrument panel cluster DTCs are set, go to next step. If any instrument panel cluster DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
3. Turn ignition off. Disconnect fuel level sensor harness connector. Connect Signal Generator/Instrument Panel Tester (J 33431-B) to fuel level sensor signal circuit (Purple wire) and fuel level sensor ground circuit (Black/White wire) of fuel level sensor harness connector. Set signal generator tester resistance to 40 ohms. Turn ignition on. Using scan tool, clear any DTCs. Using scan tool, observe fuel level display. Slow turn signal generator tester dial until resistance reaches 248 ohms. If fuel level steadily increases from zero percent to 100 percent, go to next step. If fuel level does not increase as specified, go to step 5 .
4. Turn ignition off. Set signal generator tester resistance to 40 ohms. Turn ignition on. Using scan tool, clear any DTCs. Observe fuel level gauge on instrument cluster. Slow turn signal generator tester dial until resistance reaches 248 ohms. If fuel level steadily increases from empty to full, go to step 6 . If fuel level does not increase as specified, repair fuel gauge. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
5. Turn ignition off. Disconnect PCM harness connector C2. Check for poor connections at fuel level sensor and PCM. Check for high resistance in fuel level sensor signal circuit (Purple wire) and fuel level sensor ground circuit (Black/White wire). Using DVOM, check for continuity between fuel level sensor signal circuit (Purple wire) and chassis ground. Continuity should not exist. Using DVOM, check for continuity between fuel level sensor signal circuit (Purple wire) and all other circuits in PCM harness connector and fuel tank connector. Continuity should not exist. If problem exists, repair as necessary. If problem does not exist, go to step 8 .
6. Check for poor connection at fuel level sensor. If problem exists, repair as necessary. If problem does not exist, go to next step.
7. Replace fuel level sensor.
8. Replace PCM.

1. Manifold Absolute Pressure (MAP) Sensor Diagnosis (2.2L & 2.4L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Turn ignition on, with engine off. Install scan tool. Using scan tool, retrieve DTCs. If no DTCs are set, go to next step. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
3. Compare BARO reading with that of a known-good vehicle. If readings are within .435 psi (3 kPa) of each other, go to next step. If readings are not within .435 psi (3 kPa) of each other, go to step 5 .
4. Disconnect and plug vacuum source to MAP sensor. Connect hand-held vacuum pump to vacuum source port on MAP sensor. Using scan tool, observe MAP sensor voltage reading. Apply 10 in. Hg of vacuum to MAP sensor while observing MAP sensor voltage reading on scan tool. Subtract this reading from the first reading taken before vacuum was applied. If difference is greater than 1.5 volts, go to step 6 . If difference is not greater than 1.5 volts, go to step 7 .
5. Turn ignition off. Replace MAP sensor. After repairs, go to step 9 .
6. Check MAP sensor vacuum source for leakage or restriction, and that vacuum source only supplies MAP sensor. If problem exists, go to step 8 . If problem does not exist, go to step 9 .
7. Turn ignition off. Check for poor connection at MAP sensor. If problem does not exist, go to step 5 . If problem exists, repair as necessary and go to step 9 .
8. Turn ignition off. Repair MAP sensor vacuum source as necessary and go to next step.
9. Start engine and operate vehicle under conditions which original symptom was noted. If system operates properly, system is okay. If system does not operate properly, go to step 2 .

1. Manifold Absolute Pressure (MAP) Sensor Diagnosis (3.1L, 3.4L & 3.8L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Check for the following conditions. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 14 . MAP sensor seal damaged or missing. Vacuum hoses disconnected, damaged or incorrectly routed. Intake manifold vacuum leaks. Vacuum leak at throttle body. Vacuum leaks in EGR system. Faulty PCV system.
3. Disconnect MAP sensor harness connector. Using scan tool, observe MAP sensor parameter. If scan tool displays zero volts, go to next step. If scan tool does not display zero volts, go to step 12 .
4. Using a test light connected to battery voltage, probe MAP sensor signal circuit (Light Green wire) at MAP sensor harness connector. Observe MAP sensor parameter. If scan tool displays 4.95 volts, go to next step. If scan tool does not display 4.95 volts, go to step 8 .
5. Connect a fused jumper wire between MAP sensor signal circuit (Light Green wire) and MAP sensor reference voltage circuit (Gray wire) at MAP sensor harness connector. Observe MAP sensor parameter. If scan tool displays 4.95 volts, go to next step. If scan tool does not display 4.95 volts, go to step 7 .
6. Turn ignition off. Disconnect PCM harness connectors. Check for an open or high resistance in MAP sensor ground circuit (Orange/Black wire or Black wire). Also, check for poor connections at PCM. If problem does not exist, go to step 10 . If problem exists, repair as necessary and go to step 14 .
7. Check for an open or high resistance in MAP sensor reference voltage circuit (Gray wire). Also, check for poor connections at PCM. If problem does not exist, go to step 9 . If problem exists, repair as necessary and go to step 14 .
8. Turn ignition off. Disconnect PCM harness connectors. Check for an open, high resistance or short to ground in MAP sensor signal circuit (Light Green wire). Also, check for poor connections at PCM. If problem does not exist, go to step 9 . If problem exists, repair as necessary and go to step 14 .
9. Check for poor connection at MAP sensor signal circuit (Light Green wire) of PCM. If problem does not exist, go to step 13 . If problem exists, repair as necessary and go to step 14 .
10. Check for poor connection at MAP sensor. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 14 .
11. Replace MAP sensor. After repairs, go to step 14 .
12. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Check for short to voltage in MAP sensor reference voltage circuit (Gray wire) . If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 14 .
13. Replace PCM. After repairs, go to next step.
14. Start engine and let idle. While observing MAP sensor parameter on scan tool, increase engine RPM. If MAP sensor valve changes, system is okay. If MAP sensor valve does not change, go to step 2 .

1. Park Neutral Position (PNP) Switch Diagnosis (5.7L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Install scan tool. Turn ignition on, with engine off. Place transmission in Park. Using scan tool, observe PNP switch parameter. If scan tool displays P-N---, go to next step. If scan tool does not display P-N---, go to step 4 .
3. Shift transmission into Drive. If scan tool displays -R-OD21, check for intermittent. A PNP switch that does not close or an open in signal circuit may cause engine idle speed to decrease when vehicle is shifted into gear. A PNP switch that will not open or a short to ground in signal circuit will cause EGR system to be inoperative possibly resulting in spark knock. Inspect all related wiring and connectors for poor connections or damage. If scan tool does not display -R-OD21, go to step 7 .
4. Disconnect PNP switch harness connector. Connect a fused jumper wire between PNP switch signal circuit (Orange/Black wire) and PNP switch ground circuit (Black/White wire) at PNP switch harness connector. If scan tool does not display P-N---, go to next step. If scan tool displays P-N---, go to step 10 .
5. Connect a fused jumper wire between PNP switch signal circuit (Orange/Black wire) at PNP switch harness connector and chassis ground. If scan tool does not display P-N---, leave jumper wire connected and go to next step. If scan tool displays P-N---, go to step 13 .
6. Turn ignition off. Disconnect PCM harness connector C1. Using a test light connected to battery voltage, probe PNP signal circuit (Orange/Black wire) at PCM harness connector. If test light does not illuminate, go to step 11 . If test light illuminates, go to step 9 .
7. Disconnect PNP switch harness connector. Using scan tool, observe PNP switch parameter. If scan tool does not display -R-OD21, go to next step. If scan tool displays -R-OD21, go to step 10 .
8. Turn ignition off. Disconnect PCM harness connector C1. Turn ignition on. If scan tool displays -R-OD21, go to step 12 . If scan tool does not display -R-OD21, go to step 15 .
9. Check for poor connection at PCM. If problem does not exist, go to step 15 . If problem exists, repair as necessary and go to step 16 .
10. Check for poor connection at PNP switch or PNP switch not properly adjusted. If problem does not exist, go to step 14 . If problem exists, repair as necessary and go to step 16 .
11. Repair open in PNP switch signal circuit (Orange/Black wire). After repairs, go to step 16 .
12. Repair short to ground in PNP switch signal circuit (Orange/Black wire). After repairs, go to step 16 .
13. Repair open in PNP switch ground circuit (Black/White wire). After repairs, go to step 16 .
14. Replace PNP switch. After repairs, go to step 16 .
15. Replace PCM. After repairs, go to next step.
16. Operate vehicle within conditions under which symptom was noted. If system operates properly, system is okay. If system does not operate properly, go to step 2 .

MODULES, MOTORS, RELAYS & SOLENOIDS

Note. Manufacturer does not provide testing procedures for many individual systems and components. For module, motor, relay and solenoid testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Secondary AIR Electric Air Pump (5.7L)

Locate secondary AIR electric air pump on left front frame rail, in engine compartment. Disconnect 3-pin connector from electric air pump. Apply ground to terminal "C" (Black wire) of pump. Apply battery voltage with a fused jumper wire to terminal "A" (Red wire) of pump. Pump should run. If pump does not operate, replace pump.

Idle Air Control (IAC) Motor

See IDLE CONTROL SYSTEM .

A/C Compressor Clutch Relay

See appropriate MANUAL A/C-HEATER SYSTEMS or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.

Fuel Pump Relay

Fuel pump relay is located in underhood fuse/relay block. To test fuel pump relay, see FUEL SYSTEM ELECTRICAL CIRCUIT under appropriate NO START - ENGINE CRANKS OKAY in appropriate BASIC DIAGNOSTIC PROCEDURES article.

SOLENOIDS

All PCM-controlled solenoids should have at least 20 ohms of resistance when checked with positive ohmmeter lead connected to power supply terminal of solenoid and negative ohmmeter lead connected to ground terminal of solenoid. Some solenoids are equipped with internal diodes. On these solenoids, resistance values will differ if ohmmeter test leads are reversed.

FUEL SYSTEM

Note. For fuel system pressure testing, see appropriate BASIC DIAGNOSTIC PROCEDURES article.

Manufacturer does not provide testing procedures for many individual systems and components. For fuel system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Fuel Pressure Regulator

To test fuel pressure regulator, see appropriate FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.

FUEL CONTROL

Note. Retrieve DTCs and perform appropriate DTC test before performing FUEL INJECTOR CIRCUIT DIAGNOSIS. See appropriate SELF-DIAGNOSTICS article. Also, ensure all mechanical and ignition coil/module circuit malfunctions are repaired before performing fuel injector circuit diagnosis.

See RELAYS under MODULES, MOTORS, RELAYS & SOLENOIDS.

IDLE CONTROL SYSTEM

Note. For idle control system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

1. Idle Air Control (IAC) System Diagnosis (3.1L, 3.4L, 3.5L & 3.8L) If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Install scan tool. Start engine. Turn all accessories off. Using scan tool, command idle up to 1500 RPM, then down to 650 RPM and then back up to 1500 RPM. If engine speed responded as commanded within 50 RPM, system is okay. If engine speed did not respond as commanded within 50 RPM, go to next step.
3. Turn ignition off. Connect IAC Driver (J-37027-A) to IAC valve. Set parking brake and block wheels. Start engine and let idle. Using scan tool, command idle up to 1500 RPM, then down to 650 RPM and then back up to 1500 RPM, while observing noid lights on IAC driver. If noid lights do not cycle Red and Green or turn off, go to next step. If noid lights cycle Red and Green but never off, go to step 5 .
4. Check for open, short to voltage or short to ground in IAC circuits between IAC valve and PCM. If problem does not exist, go to step 10 . If problem exists, repair as necessary and go to step 12 .
5. If low idle or rich condition exists, go to next step. If low idle or rich condition does not exist, go to step 7 .
6. Check for the following conditions: throttle body damage, restricted intake system or air filter element, collapsed air intake duct, clogged IAC passages in throttle body, and intake leaks. If problem does not exist, go to step 8 . If problem exists, repair as necessary and go to step 12 .
7. Check for the following conditions: vacuum leaks, damaged throttle body, throttle linkage binding, misadjusted throttle cable, misadjusted cruise control cable, and faulty PCV system. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 12 .
8. Check for poor connection at IAC valve. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 12 .
9. Replace IAC valve. After repairs, go to step 12 .
10. Check for poor connection at PCM. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 12 .
11. Replace PCM. After repairs, go to next step.
12. Clear all DTCs. Start engine. Ensure all accessories are off. Using scan tool, command idle up to 1500 RPM, then down to 650 RPM and then back up to 1500 RPM. If engine speed responded as commanded within 50 RPM, system is okay. If engine speed did not respond as commanded within 50 RPM, go to step 3 .

IGNITION SYSTEM

Note. For basic ignition system checks, see appropriate BASIC DIAGNOSTIC PROCEDURES article.

For ignition system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

EMISSION SYSTEMS & SUBSYSTEMS

Note. For emission and subsystem testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

AIR Pump (Belt-Driven)

Accelerate engine to approximately 1500 RPM and observe airflow from hoses. If airflow increases as engine is accelerated, pump is working properly. If airflow does not increase, check hoses, pump belt tension, leaky valves or defective air injection pump.

Check Valve

Detach check valve and blow through valve in direction of check valve flow (to cylinder head). Attempt to suck air back. Replace valve if airflow is allowed against the direction of flow.

Electric AIR Pump Relay (5.7L)

1. Start engine. With engine operating in open loop, electric air pump should run and air should be coming out of electric air pump exhaust port.
2. If electric air pump is operating, allow engine to idle for at least 3 minutes. With vehicle in closed loop (or about 3 minutes after start), PCM should de-energize electric air pump relay and electric air pump should stop. If air pump does not operate as described, go to next step. If air pump operates as described, relay is functioning properly.
3. Remove air pump relay from fuse/relay block. Air pump should stop. If air pump stops, check or replace faulty relay. If air pump does not stop, check circuit to air pump for a short to battery voltage.

EXHAUST GAS RECIRCULATION (EGR)

Manufacturer does not provide testing procedures for many individual systems and components. For EGR system testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

Exhaust System Check

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Remove heated oxygen sensor. Install exhaust backpressure tester in place of oxygen sensor. Start engine and let idle. If pressure reading is not 1.25 psi or greater on all models except 2.2L and 2.4L engine, or .5 psi or greater on 2.2L and 2.4L engine, go to next step. If pressure reading is 1.25 psi or greater on all models except 2.2L and 2.4L engine, or .5 psi or greater on 2.2L and 2.4L engine, go to step 4 .
3. Increase engine speed to 2000 RPM (3000 RPM on 2.2L and 2.4L). If pressure reading is greater than 3 psi on all models except 2.2L and 2.4L engine, or .75 psi or greater on 2.2L and 2.4L engine, go to next step. If pressure reading is not greater than 3 psi on all models except 2.2L and 2.4L engine, or .75 psi or greater on 2.2L and 2.4L engine, go to step 6 .
4. Check exhaust system for crushed pipe, internal muffler damage or heat distress. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 6 .
5. Replace catalytic converter. After repairs, go to next step.
6. Operate vehicle within conditions under which original symptom was noted. If system operate properly, system is okay. If system does not operate properly, go to step 2 .

FUEL EVAPORATION

Note. Ensure all vacuum line and EVAP system components are not damaged or missing before proceeding with this test.

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

1. Rough idle.
2. Stalling or slow idle speed.
3. Oil leaks.
4. Oil in air cleaner.
5. Sludge in engine.

A leaking PCV valve or hose could cause

1. Rough idle.
2. Stalling.
3. High idle speed.

If engine idles rough, check for clogged PCV valve, or plugged or broken hoses BEFORE adjusting idle. Check PCV valve application to ensure correct valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

1. Disconnect PCV valve vacuum hose from cylinder head cover. Run engine at idle. Place thumb over open end of PCV valve vacuum hose to check for vacuum. If vacuum does not exist, check for obstruction in source vacuum supply. If source vacuum supply is okay, replace PCV valve.
2. Turn ignition off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
3. Visually inspect valve for varnish or deposits which may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace as necessary.
4. Engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
5. An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

Manufacturer does not provide testing procedures for many individual systems and components. For system and component testing not listed, perform related DTC testing procedure. See appropriate SELF-DIAGNOSTICS article.

A/C COMPRESSOR CLUTCH CONTROLS (EXCEPT 1.9L & 3.0L)

Note. For A/C compressor clutch circuit testing, see appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and wire color identification.

To provide improved idle quality, maintain Wide Open Throttle (WOT) performance and provide A/C system protection, compressor clutch is controlled by PCM.

For proper control of cooling fans, compressor clutch and Idle Air Control (IAC) valve, a refrigerant pressure sensor is used. PCM uses signals provided by sensor to monitor high and low side refrigerant pressures. If PCM detects a fault in refrigerant pressure circuit, compressor clutch will be disabled.

The A/C compressor clutch relay is controlled by PCM. This allows PCM to raise idle speed before engaging compressor clutch, or disable compressor clutch during WOT, high engine RPM, high power steering loads and hot engine restarts. PCM also disables compressor clutch if coolant temperature becomes excessive. For location of A/C compressor clutch relay, see A/C COMPRESSOR CLUTCH RELAY LOCATION table.

A/C COMPRESSOR CLUTCH RELAY LOCATION

Note. To help save diagnostic time, check for blown fuses or fusible links before proceeding with any testing. If fuses are blown, locate and repair short circuit before replacing fuses. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary.

A/C COMPRESSOR CLUTCH CONTROLS (1.9L)

Note. For A/C compressor clutch circuit diagnosis, see appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.

Engine Coolant Temperature

Powertrain Control Module (PCM) will de-energize A/C compressor clutch relay when engine temperature is 244°F (118°C) and energize A/C compressor clutch relay when engine temperature is less than 234°F (112°C). A/C compressor clutch relay is located in underhood junction block.

Wide Open Throttle (WOT)

On A/T, PCM will de-energize A/C compressor clutch relay for 15 seconds when TP sensor angle is greater than 95 percent. On M/T, PCM will de-energize A/C compressor clutch relay for 15 seconds when TP sensor angle is greater than 90 percent and energize A/C compressor clutch relay when TP sensor angle is less than 95 percent for 2 seconds.

Compressor Over-Speed Protection

PCM will de-energize A/C compressor clutch relay when engine speed is greater than 6375 RPM. PCM will energize A/C compressor clutch relay when engine speed is less than 4500 RPM for 2 seconds.

Low Ambient Temperature Protection

PCM will cycle compressor clutch on and off once every 90 seconds if ambient air temperature is 40-60°F (4-16°C) and vehicle speed is greater than zero MPH.

High/Low Pressure Cut-Out Switch

High/low pressure cut-out switch is a dual-pressure switch located forward of left front strut tower on liquid line. Switch contains 2 sets of contacts. PCM disengages compressor clutch if either set of contacts open.

PCM will de-energize A/C compressor clutch relay when discharge pressure is greater than 380-401 psi (26.7-28.2 kg/cm 2 ) and energize A/C compressor clutch relay when discharge pressure is 200-251 psi (14.1-17.6 kg/cm 2 ). PCM will energize cooling fan relay for 180 seconds after A/C compressor clutch relay is de-energized because of pressure switch activation. PCM will de-energize A/C compressor clutch relay if discharge pressure is less than 40 psi (2.8 kg/cm 2 ).

A/C COMPRESSOR CLUTCH CONTROLS (3.0L)

Note. For A/C compressor clutch circuit testing, see appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and wire color identification.

When A/C button on A/C-heater control panel is pressed, an A/C request signal is sent through the refrigerant pressure switch and Engine Control Module (ECM) to the coil of A/C compressor clutch relay (K60). The A/C compressor clutch relay is located at left front of engine compartment, in ECM housing. This enables A/C compressor clutch relay to energize, allowing ignition voltage to energize compressor clutch coil and fan control relay (K87).

When fan control relay energizes, battery voltage is supplied to auxiliary cooling fan No. 1, and through the normally open contacts of fan control relay (K52), to auxiliary cooling fan No. 2. If coolant temperature reaches 248°F (120°C), secondary temperature switch contacts will open and the compressor clutch coil is disengaged, causing A/C system to turn off. Secondary temperature switch will not allow A/C system to turn back on until coolant temperature has dropped to 239°F (115°C) or less.

Compressor clutch coil can also be turned off by refrigerant pressure switches (low pressure switch or high pressure switch). Low pressure switch will turn compressor clutch off as soon as refrigerant pressure falls to about 26 psi (1.8 kg/cm 2 ). This is done by opening the low pressure switch contacts and not allowing battery voltage to pass through A/C compressor clutch relay (K60) to compressor clutch coil. Low pressure switch activates the compressor clutch when refrigerant pressure increases to about 36.3 psi (2.6 kg/cm 2 ).

High pressure switch will turn compressor clutch off as soon as refrigerant pressure exceeds about 435 psi (30.6 kg/cm 2 ). This is done by opening the high pressure switch contacts in refrigerant pressure switch and not allowing battery voltage to pass through A/C compressor clutch relay (K60) to compressor clutch. High pressure switch activates compressor clutch when refrigerant pressure drops to less than about 290 psi (19.3 kg/cm 2 ).

When refrigerant pressure exceeds about 159.4 psi (11.2 kg/cm 2 ), A/C control switch contacts will close and engine idle speed will increase to compensate for RPM drop that occurs when A/C system is switched on. A/C control switch is installed in high pressure line, between A/C compressor and condenser. When refrigerant pressure drops to less than about 130.5 psi (9.2 kg/cm 2 ), A/C control switch contacts will close and allow engine idle speed to return to normal.

ELECTRIC COOLING FAN CONTROL (EXCEPT 1.9L & 3.0L)

Note. For electric cooling fan circuit testing, see ELECTRIC COOLING FANS article in AIR CONDITIONING & HEATING. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and wire color identification.

All FWD and some RWD vehicles use an electric cooling fan. The electric cooling fan is used for radiator and A/C condenser cooling. Cooling fan operates when A/C is on and when engine coolant temperature exceeds a specific value. One or more cooling fan relays may be used. For location of cooling fan relay, see COOLING FAN RELAY LOCATION table.

COOLING FAN RELAY LOCATION

To help save diagnostic time, ALWAYS check for blown fuses or fusible links before proceeding with any testing. If fuses are blown, locate and repair short circuit before replacing fuses. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. For component location, and terminal and wire color identification, see appropriate wiring diagram in WIRING DIAGRAMS article.

ELECTRIC COOLING FAN CONTROL (1.9L)

Note. For electric cooling fan circuit testing, see ENGINE COOLING FANS article in AIR CONDITIONING & HEATING. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and wire color identification.

Cooling Fan Logic

PCM will energize cooling fan relay when an A/C request signal is received from A/C switch, or when coolant temperature is greater than 223°F (106°C). Fan will operate for 180 seconds after A/C request signal is canceled. PCM will de-energize cooling fan relay when vehicle speed is greater than 70 MPH for 180 seconds. Cooling fan relay is located in underhood junction block.

ELECTRIC COOLING FAN CONTROL (3.0L)

Note. For electric cooling fan circuit testing, see ENGINE COOLING FANS article in AIR CONDITIONING & HEATING. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and wire color identification.

Electric cooling fan circuits consist of one engine cooling fan, 2 auxiliary cooling fans, 2 temperature switches, A/C refrigerant pressure switch, Engine Control Module (ECM) cooling blower, timing control pump, auxiliary water pump, 5 fan control relays, one ECM relay, one auxiliary water pump relay and one engine cooling fan resistor. Relays are located at left front of engine compartment, in ECM housing. Auxiliary water pump is provided with battery voltage with ignition on, and when coolant temperature reaches 194°F (90°C).

At 212°F (100°C), primary temperature switch stage one contacts will close, enabling ECM relay (K48) and cooling fan control relay (K26) to energize. When ECM relay energizes, ignition voltage is applied to ECM cooling blower, allowing it to operate.

When cooling fan control relay (K26) energizes, battery voltage is applied to auxiliary cooling fan No. 1 and to auxiliary cooling fan No. 2 through the normally open contacts of fan control relay (K52). This allows auxiliary cooling fans to operate in series at half speed.

Fan control relay (K26) supplies battery voltage to engine cooling fan through the engine cooling fan resistor. The engine cooling fan resistor limits engine cooling fan operation to half speed. Fan control relay (K26) will also supply battery voltage to timing control pump through normally closed contacts of the auxiliary water pump relay (K22). This will allow timing control pump to operate.

Primary temperature switch stage one contacts will open when coolant temperature reaches 203°F (95°C). This will turn on all 3 fans, ECM cooling blower and turn the timing control pump off, unless A/C system is on.

If ignition switch is off and coolant temperature is greater than 212°F (100°C), both auxiliary cooling fans, engine cooling fan and timing control pump will remain on until coolant temperature drops to less than 203°F (95°C).

If temperature reaches 221°F (105°C), temperature switch contacts will close enabling fan control relays (K52 and K28) to energize. When fan control relay (K52) energizes, auxiliary cooling fan No. 1 runs at full speed as it is no longer in series with auxiliary cooling fan No. 2. When fan control relay (K28) energizes, battery voltage is applied to auxiliary cooling fan No. 2 which runs at full speed.

With primary temperature switch stage one contacts closed, ECM cooling blower, timing control pump and engine cooling fan (half speed) will continue to operate. Secondary temperature switch contacts will open when coolant temperature reaches 212°F (100°C) and cause operation of auxiliary cooling fans to operate differently as designated by primary temperature switch.

If coolant temperature reaches 230°F (110°C), secondary temperature switch stage 2 contacts will close, enabling fan control relay (K67) to energize. When fan control relay (K67) energizes, battery voltage is applied directly to engine cooling fan causing it to run at full speed. All other operations that were taking place before coolant temperature reached 230°F (110°C) remain in effect. Primary temperature switch stage 2 contacts open when coolant temperature reaches 221°F (105°C) and engine cooling fan will return to half speed.

At coolant temperatures greater than about 230°F (110°C), all 3 cooling fans run at full speed. ECM cooling blower, timing control pump and auxiliary water pump are also operating. Only 6 of the 7 relays operate at this time, unless A/C system is on. In this case, fan control relay (K87) and A/C compressor clutch relay (K60) will also operate.

To prevent excessively high refrigerant pressure, auxiliary cooling fans are switched from first speed to second speed at refrigerant pressures greater than about 276 psi (19.4 kg/cm 2 ). When pressure drops to less than about 218 psi (15.3 kg/cm 2 ), auxiliary cooling fans are switched back to first speed.

Except 5.7L

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Turn ignition on, with engine off. If charging light illuminates, go to next step. If charging light does not illuminate, go to step 4 .
3. Start engine. If charging light does not go out, go to step 5 . If charging light goes out, go to step 21 .
4. Turn ignition off. Disconnect generator harness connectors. Turn ignition on, with engine off. If charging light illuminates, go to step 6 . If charging light does not illuminate, go to step 7 .
5. Turn ignition off. Install scan tool. Turn ignition on. Ensure all accessories are off. Using scan tool, observe generator voltage. If scan tool displays battery voltage or less, go to step 8 . If scan tool displays greater than battery voltage, go to step 9 .
6. Using a test light connected to ground, probe charging light signal circuit at generator harness connector. If test light illuminates, go to step 10 . If test light does not illuminate, go to step 11 .
7. Turn ignition off. Replace or repair instrument cluster and/or charging light bulb as necessary. After repairs, go to step 21 .
8. Using scan tool, check generator PWM value. If scan tool displays greater than 5 percent, go to step 7 . If scan tool does not display greater than 5 percent, go to step 12 .
9. Turn ignition off. Disconnect generator harness connectors. Turn ignition on, with engine off. Using a test light connected to battery voltage, probe charging light signal circuit at generator harness connector. If test light illuminates, go to step 13 . If test light does not illuminate, go to step 14 .
10. Locate and repair short to voltage in charging light control signal circuit. After repairs, go to step 21 .
11. Replace generator. After repairs, go to step 21 .
12. Turn ignition off. Disconnect generator harness connectors. Turn ignition on, leaving engine off. Using a test light connected to battery voltage, probe generator field circuit at generator harness connector. If test light illuminates, go to step 15 . If test light does not illuminate, go to step 16 .
13. Locate and repair short to ground in charging light control signal circuit. After repairs, go to step 21 .
14. Using DVOM connected to ground, measure voltage at charging light signal circuit of generator harness connector. If voltage is greater than 4.5 volts, go to step 17 . If voltage is less than 4.5 volts, go to step 18 .
15. Locate and repair short to ground in generator field circuit. After repairs, go to step 21 .
16. Locate and repair poor connection and/or open in generator field circuit. After repairs, go to step 21 .
17. Using DVOM connected to ground, measure voltage at battery voltage supply circuit of generator harness connector. If battery voltage exist, go to step 11 . If battery voltage does not exist, go to step 19 .
18. Locate and repair poor connection and/or open in charging light signal circuit of generator harness connector. After repairs, go to step 21 .
19. Locate and repair poor connection and/or open in battery voltage supply circuit of generator harness connector. After repairs, go to step 21 .
20. Check for poor connections at PCM. If connections are okay, replace PCM. After repairs, go to next step.
21. Operate vehicle under condition under which original symptom was noted. If system does not operate properly, go to step 2 .

5.7L

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Install scan tool. Start engine. Using scan tool, monitor generator terminal "L" terminal. If scan tool displays generator terminal "L" active, perform DTC P1637 test. See appropriate SELF-DIAGNOSTICS article. If scan tool does not display generator terminal "L" active, go to next step.
3. Using DVOM, measure voltage at battery. If voltage is 13-15 volts, check for low battery charge. A shorted output diode, malfunctioning regulator, an open or shorted rotor, or an open sense lead in generator may cause a low battery charge. If voltage is not 13-15 volts, go to next step.
4. Using test light connected to ground, probe generator battery feed circuit. If test light illuminates, go to next step. If test light does not illuminate, check charging system.
5. Disconnect generator harness connector. Start engine. Using DVOM, measure voltage between ground and generator harness connector terminal "B" (Brown wire). If voltage is 10 volts or more, go to step 10 . If voltage is less than 10 volts, go to next step.
6. Turn ignition off. Disconnect PCM harness connector C2. Using DVOM, check for continuity between generator harness connector terminal "B" (Brown wire) and PCM harness connector C2 terminal No. 15 (Brown wire). If continuity exists, go to step 8 . If continuity does not exist, go to next step.
7. Repair open or high resistance in generator circuit (Brown wire).
8. Check for poor connection at PCM. Repair as necessary. If connection is okay, go to next step.
9. Replace PCM.
10. Check for poor connection at generator. Repair as necessary. If connection is okay, go to next step.
11. Replace generator.

3.5L

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Ensure battery is properly connected and fully charged. Turn ignition on. If starter cranks engine, check for intermittent. See appropriate TROUBLE SHOOTING - NO CODES article. If starter does not crank engine, go to next step.
3. Connect test light between ground and starter solenoid terminal "S". Turn ignition on. Observe test light. If test light illuminates, PCM controlled portion of starter is okay. Check starting system. If test light does not illuminate, go to next step.
4. Using scan tool, retrieve DTCs. Check for DTCs P1610, P1626, P1631 or any anti-theft system DTCs. If no DTCs are set, go to next step. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article or appropriate ANTI-THEFT SYSTEM article in ACCESSORIES & EQUIPMENT.
5. Using scan tool, monitor crank request. If scan tool displays NO with ignition switch in ON position and YES with ignition switch in START position, go to next step. If scan tool display is not as specified, diagnose crank request signal circuit (Purple wire) between PCM and fuse block. Check 10-amp crank fuse in fuse block. Replace as necessary. Check for open, shorts or poor connections in crank request signal circuit (Purple wire) between PCM and fuse block. Repair as necessary. Check for faulty ignition switch. Replace as necessary. If fuse, circuit and ignition switch are okay, replace PCM.
6. Using scan tool, monitor driver status for starter enable (crank) relay. Turn ignition switch from ON position to START position. If scan tool displays OK with ignition on both positions, go to next step. If scan tool does not display as specified, diagnose crank relay control circuit (Yellow/Black wire) between PCM and underhood fuse block assembly. Check for open, shorts or poor connections in ignition feed circuit (Pink wire) between fuse block and CRANK relay. Repair as necessary. Check for open, shorts or poor connections in crank relay control circuit (Yellow/Black wire) between CRANK relay and PCM. Repair as necessary. Check for faulty CRANK relay. If circuits and relay are okay, replace PCM.
7. Place transmission in Park. Turn ignition on. If starter operates, go to step 20 . If starter does not operate, go to next step.
8. Check 40-amp CRANK maxifuse located in underhood fuse block assembly. If fuse is okay, go to step 14 . If fuse is blown, go to next step.
9. Remove CRANK relay from underhood fuse block assembly. Using DVOM connected to battery ground, probe battery positive voltage circuit (Pink wire) at CRANK relay connector. If resistance is greater than 2 ohms, go to next step. If resistance is less than 2 ohms, go to step 22 .
10. Disconnect starter solenoid control circuit (Purple wire) at starter solenoid. Using DVOM connected to battery ground, probe starter solenoid control circuit (Purple wire). If resistance is greater than 2 ohms, go to step 12 . If resistance is less than 2 ohms, go to next step.
11. Disconnect transaxle range switch connector C1. Using DVOM connected to battery ground, probe solenoid control circuit (Purple wire) to starter solenoid and solenoid control circuit (Yellow wire) to CRANK relay. If resistance is greater than 2 ohms on either circuit, go to step 26 . If resistance is less than 2 ohms on either circuit, go to step 28 .
12. Leave starter solenoid control circuit (Purple wire) disconnected from starter. Ensure circuit will not ground out on any metal surface. Replace 40-amp CRANK maxifuse. Reinstall CRANK relay. Turn ignition switch to START position. Recheck 40-amp CRANK maxifuse. If fuse is okay, go to next step. If fuse is blown, go to step 34 .
13. Reconnect starter solenoid control circuit (Purple wire) to starter. Turn ignition switch to START position. Recheck 40-amp CRANK maxifuse. If fuse is okay, check starting system. If fuse is blown, go to step 36 .
14. Remove CRANK relay from underhood fuse block assembly. Using a test light connected to ground, probe battery positive voltage circuit (Pink wire) at CRANK relay connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 24 .
15. Connect a jumper wire between battery positive voltage circuit (Pink wire) and solenoid control circuit (Yellow wire) of CRANK relay connector. If starter operates, go to step 33 . If starter does not operate, go to next step.
16. Leave jumper wire connected. Disconnect transaxle range switch connector C1. Using a test light connected to ground, probe transaxle range switch connector C1 terminal "G" (Yellow wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 25 .
17. Leave jumper wire connected. Connect a jumper wire between transaxle range switch connector C1 terminal "G" (Yellow wire) and terminal "E" (Purple wire). If starter operates, go to step 27 . If starter does not operate, go to next step
18. Leave jumper wire connected. Connect test light between solenoid control circuit (Purple wire) of starter solenoid and metal surface of solenoid housing. If test light illuminates, go to step 35 . If test light does not illuminate, go to next step.
19. Move test light ground clip to a known good ground. Probe solenoid control circuit (Purple wire) of starter solenoid. If test light illuminates, go to step 32 . If test light does not illuminate, go to step 25 .
20. Turn ignition off. Disconnect PCM harness connector C2. If starter operates with ignition switch in ON position, go to next step. If starter does not operate with ignition switch in ON position, go to step 30 .
21. Remove CRANK relay from underhood fuse block assembly. If starter operates with ignition switch in ON position, go to step 29 . If starter does not operate with ignition switch in ON position, go to step 34 .
22. Repair short to ground in battery positive voltage circuit (Pink wire) to CRANK relay. After repairs, go to step 37 .
23. Repair short to ground in solenoid control circuit (Purple wire) After repairs, go to step 37 .
24. Repair open or high resistance in battery positive voltage circuit (Pink wire) to CRANK relay. After repairs, go to step 37 .
25. Repair open or high resistance in solenoid control circuit (Purple wire). After repairs, go to step 37 .
26. Repair short to ground in affected circuit. After repairs, go to step 37 .
27. Check for poor connections at transaxle range switch or for transaxle range switch out of adjustment. If problem does not exist, go to next step. If problem exists, repair as necessary, and go to step 37 .
28. Replace transaxle range switch. After repairs, go to step 37 .
29. Check for a short to voltage in solenoid control circuit (Purple wire), for shorted or poor connection at starter solenoid, or for a faulty starter solenoid. After repairs, go to step 37 .
30. Replace PCM. After repairs, go to step 37 .
31. Replace CRANK relay. After repairs, go to step 37 .
32. Check for loose solenoid/starter motor or corrosion on mounting surface causing loss of ground continuity. Repair as necessary. After repairs, go to step 37 .
33. Check for poor connection at CRANK relay connector. If problem does not exist, go to next step. If problem exists, repair as necessary an go to step 37 .
34. Replace CRANK relay. After repairs, go to step 37 .
35. Check for poor connection at starter solenoid. If problem does not exist, go to next step. If problem exists, repair as necessary an go to step 37 .
36. Replace starter solenoid. After repairs, go to step 37 .
37. Turn ignition switch to START position. If starter operates, system is okay. If starter does not operate, go to step 2 .

3.1L, 3.5L & 3.8L

1. Check instrument cluster. See appropriate INSTRUMENT PANELS - ELECTRONIC article in ACCESSORIES & EQUIPMENT. If instrument cluster is okay, go to next step.
2. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
3. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using DVOM, measure voltage between ground and tachometer control circuit (White wire) at PCM harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 7 .
4. Set DVOM to 10-amp scale. Using DVOM, measure current between ground and tachometer control circuit (White wire) at PCM harness connector. Monitor reading for about 2 minutes. If reading is less than 0.5 amp, go to step 12 . If reading is not less than 0.5 amp, go to next step.
5. Disconnect instrument cluster harness connectors. Leave PCM harness connectors disconnected. Using DVOM, measure voltage between ground and tachometer control circuit (White wire) at PCM harness connector. If voltage is zero volts, go to step 15 . If voltage is not zero volts, go to next step.
6. Locate and repair short to voltage in tachometer control circuit (White wire) between instrument cluster and PCM. After repairs, go to step 17 .
7. Check ignition feed fuse for instrument cluster. If fuse is blown, go to next step. If fuse is okay, go to step 9 .
8. Locate and repair short to ground in ignition feed circuit (Pink wire) to instrument cluster or a shorted component. Replace fuse. After repairs, go to step 17 .
9. Disconnect instrument cluster connectors. Turn ignition on. Using DVOM, measure voltage between ground and ignition feed circuit (Pink wire) at instrument cluster harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 14 .
10. Check for open or short to ground in tachometer control circuit (White wire) between instrument cluster and PCM. If problem exists, repair as necessary and go to step 17 . If problem does not exist, go to next step.
11. Check tachometer control circuit and ignition feed circuit for poor connection at instrument cluster and PCM. If problem exists, repair as necessary and go to step 17 . If problem does not exist, go to step 15 .
12. Check for poor connections at PCM. If problem does not exist, go to step 16 . If problem exists, repair as necessary and go to step 17 .
13. Check tachometer control circuit for poor connection at PCM. If problem exists, repair as necessary and go to step 17 . If problem does not exist, go to step 16 .
14. Locate and repair open in ignition feed circuit to instrument cluster. After repairs, go to step 17 .
15. Repair or replace instrument cluster. After repairs, go to step 17 .
16. Replace PCM. After repairs, go to next step.
17. Start engine. Observe tachometer. If tachometer is operating properly, system is okay. If tachometer is not operating properly, repair instrument cluster as necessary. See appropriate INSTRUMENT PANELS - ELECTRONIC article in ACCESSORIES & EQUIPMENT.

3.4L & 3.8L

1. If On-Board Diagnostic (OBD) system check has been performed, go to next step. If On-Board Diagnostic (OBD) system check has not been performed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.
2. Check instrument cluster. See appropriate INSTRUMENT PANELS - ELECTRONIC article in ACCESSORIES & EQUIPMENT. If instrument panel is okay, go to next step.
3. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using DVOM, measure voltage between affected PCM output circuit and ground. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 7 .
4. Set DVOM to 10-amp scale. Using DVOM, measure current between affected PCM output circuit and ground. See appropriate wiring diagram in WIRING DIAGRAMS article. Monitor reading for about 2 minutes. If current reading remains .05-1.5 amps, go to step 12 . If current reading does not remain .05-1.5 amps, go to next step.
5. Turn ignition off. Disconnect instrument cluster harness connectors. Leave PCM connectors disconnected. Using DVOM, measure voltage between affected PCM output circuit and ground. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is zero volts, go to step 15 . If voltage is present, go to next step.
6. Locate and repair short to voltage in affected PCM output circuit. After repairs, go to step 17 .
7. Check ignition feed fuse for instrument cluster indicator lights. If fuse is blown, go to next step. If fuse is okay, go to step 9 .
8. Locate and repair short to ground in ignition feed circuit for instrument cluster indicator lights. Replace fuse. After repairs, go to step 17 .
9. Disconnect instrument cluster connectors. Turn ignition on. Using DVOM, measure voltage between ignition feed circuit for instrument cluster indicator lights and ground. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 14 .
10. Check for an open or short to ground in affected PCM output circuit. If problem exists, repair as necessary and go to step 17 . If problem does not exist, go to next step.
11. Check affected PCM output circuit and ignition feed circuit for poor connection at instrument cluster and PCM. If problem exists, repair as necessary and go to step 17 . If problem does not exist, go to step 15 .
12. Turn ignition off. Reconnect PCM harness connectors. Disconnect instrument cluster connectors. Turn ignition on. Connect a test light between affected PCM output circuit and ignition feed circuit at instrument cluster harness connector. Using scan tool, perform OUTPUT TESTS function to cycle affected warning light on and off. If test light flashes on and off, check for shorted component or circuit in the output driver circuit. Check for faulty instrument cluster. If test light does not flash on and off, go to next step.
13. Check affected PCM output circuit for poor connection to PCM. If problem exists, repair as necessary and go to step 17 . If problem does not exist, go to step 16 .
14. Locate and repair open in ignition feed circuit to instrument cluster indicator lights. After repairs, go to step 17 .
15. Repair or replace instrument cluster as necessary. After repairs, go to step 17 .
16. Replace PCM. After repairs, go to next step.
17. Using scan tool, operate affected warning light. If warning light operates properly, system is okay. If warning light does not operate properly, go to step 2 .

TRANSMISSION

Note. Computerized transmission controls are also covered in greater detail in appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS. For component circuit identification, see appropriate wiring diagram in WIRING DIAGRAMS article.

1-4 Upshift System Check (Corvette M/T)

A malfunction in upshift system will set a related Diagnostic Trouble Code (DTC). See appropriate SELF-DIAGNOSTICS article.