LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Saturn >> 1999 >> SW2 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - System Testing & Engine Component Tests >> Engine Sensors & Switches
April 5, 2026: LEMON Manuals is launched! Read the announcement.

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. CAUTION: DO NOT remove pressure cap from surge tank while engine is at normal operating temperature.
  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. CAUTION: DO NOT remove pressure cap from surge tank while engine is at normal operating temperature.
  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 .
  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 .
  6. Repair the open in CKT 650. After repairs are complete, go to IPC DIAGNOSTIC SYSTEM CHECK .
  7. Replace the coolant level switch (located in coolant recovery bottle). After repairs are complete, go to IPC DIAGNOSTIC SYSTEM CHECK .
  8. Replace the IPC. See INSTRUMENT PANEL CLUSTER (IPC) . After repairs are complete, go to IPC DIAGNOSTIC SYSTEM CHECK .

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. NOTE: Ensure oil level is okay before performing engine oil level switch diagnosis.
  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  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  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. NOTE: Ensure oil level is okay before performing engine oil level switch diagnosis.
  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. NOTE: Ensure engine oil level is correct before proceeding with next step.
  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. NOTE: Ensure oil level is okay before performing engine oil level sensor diagnosis.
  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.
scientia non olet · About LEMON Manuals