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Home >> Buick >> 2001 >> Regal GS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0507: IAC System Rpm High >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
    2. NOTE: Ensure engine speed stabilizes with each commanded RPM change to determine if engine speed stays within 175 RPM of commanded RPM.
  2. Set parking brake and block drive wheels. Install scan tool. Start engine. Turn all accessories off. Using scan tool RPM control function, slowly increment engine speed to 1800 RPM, then to 600 RPM, and then to 1800 RPM. Exit RPM control function. If engine speed stabilizes within 175 RPM of commanded RPM during test, go to next step. If engine speed does not stabilize within 100 RPM of commanded RPM during test, go to step  4.
  3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If this DTC failed this ignition cycle, go to next step. If this DTC did not fail this ignition cycle, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect IAC valve. See Figure or Figure . Connect an IAC Motor Driver (J 37027-A) to IAC valve. Start engine. Using IAC motor driver, command IAC valve in until about 600 RPM is reached. Using IAC motor driver, command IAC valve out until about 1800 RPM is reached. Return engine speed to desired idle as indicated on scan tool data list. If engine speed steadily decreased to about 600 RPM and steadily increased to about 1800 RPM when IAC valve was commanded in and out, go to next step. If engine speed does not steadily decrease to about 600 RPM and steadily increase to about 1800 RPM when IAC valve was commanded in and out, go to step  10.
  5. Using a test light connected to ground, probe one IAC valve circuit at IAC valve harness connector. Start engine. Using IAC motor driver, command low RPM while observing scan tool until IAC counts start to increment. Using IAC motor driver, command high RPM while observing scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine idle speed to desired idle as indicated on scan tool data list. Repeat procedure for other 3 IAC valve circuits. If test light remained on (never flashing) while IAC counts where incrementing at any IAC valve circuits during test, go to step  9. If test light did not remain on (never flashing) while IAC counts where incrementing at any IAC valve circuits during test, go to next step.
  6. If test light remained off (never flashing) while IAC counts where incrementing at any IAC valve circuits during test, go to step  8. If test light did not remained off (never flashing) while IAC counts where incrementing at any IAC valve circuits during test, go to next step.
  7. Connect a test light between IAC valve connector terminals "C" (Light Blue/Black wire) and "D" (Light Blue/White wire). See Figure. Using IAC motor driver, command low RPM while observing scan tool until IAC counts start to increment. Using IAC motor driver, command high RPM while observing scan tool until IAC counts start to increment. While IAC counts are incrementing, observe test light. Return engine idle speed to desired idle as indicated on scan tool data list. Repeat procedure with test light connected between IAC valve connector terminals "A" (Light Green/Black wire) and "B" (Light Green/White wire). Return engine speed to desired idle as indicated on scan tool data list. If test light remained on (never flashing) while IAC counts where incrementing during test, see DIAGNOSTIC AIDS . If test light did not remain on (never flashing) while IAC counts where incrementing during test, go to step  14.
  8. Turn ignition off. Disconnect PCM connectors. Using DVOM, check IAC valve circuit where test light remained off for open or short to ground. If problem was found, repair as necessary. After repairs, go to step  15. If problem was not found, go to step  11.
  9. Turn ignition on. Using DVOM, check IAC valve circuit where test light remained on for short to voltage. If problem was found, repair as necessary. After repairs, go to step  15. If problem was not found, go to step  11.
  10. Visually inspect for the following conditions:
    • Throttle body damage and tampering.
    • Throttle lever screw tampering, if equipped.
    • Vacuum leaks.
    • Faulty or incorrectly-installed PCV valve and hose, if equipped.
    • Throttle shaft binding.
    • Throttle linkage or cruise control linkage binding, if equipped.

    Remove IAC valve. Inspect IAC valve for the following conditions:

    • Any debris in IAC passage.
    • Excessive deposits on throttle plate.
    • Excessive deposits in throttle bore.
    • Excessive deposits on IAC valve pintle.

    If problem was found, repair as necessary. After repairs, go to step  15. If problem was not found, go to step  12.

  11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step  15. If problem was not found, go to step  14.
  12. Check IAC valve connector for poor connections. If problem was found, repair as necessary. After repairs, go to step  15. If problem was not found, go to next step.
  13. Replace IAC valve. After repairs, go to step  15.
  14. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  15. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step. If DTC does not run and pass, go to step  2.
  16. Using scan tool, observe stored information. If scan tool displays any DTCs that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display any DTCs, system is okay.
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