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Home >> Pontiac >> 2003 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0506: Idle Control System - Low Rpm >> Diagnostic Procedures
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Diagnostic Procedures

  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: Ensure engine speed stabilizes with each commanded RPM change to determine if engine speed stays within 100 RPM of the commanded RPM.
  2. Set parking brake and block drive wheels. Install scan tool. Start engine. Turn OFF all of the accessories. With scan tool in RPM control function, slowly increment engine speed to 1700 RPM, then to 600 RPM, then to 1700 RPM. Exit the RPM control function. Does the engine speed stabilize within 100 RPM of the commanded RPM during the test? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect the IAC valve. Connect an IAC Motor Driver (J-37027-1A) to IAC valve. Start engine. With the IAC Motor Driver, command the IAC valve in until about 600 RPM is reached. With IAC Motor Driver, command the IAC valve out until about 1700 RPM is reached. Return engine speed to desired idle as indicated on scan tool data list. Did engine speed steadily decrease to about 600 RPM and steadily increase to about 1700 RPM when the IAC valve was commanded in and out? If yes, go to next step. If no, go to step  11.
  5. With a test light connected to ground, probe one of the IAC valve circuits at the IAC valve harness connector using the Connector Test Adapter Kit (J-35616-A). Start engine. With Connector Test Adapter Kit, command low RPM while observing a scan tool until the IAC counts start to increment. With Connector Test Adapter Kit, command high RPM while observing a scan tool until the IAC counts start to increment. While the IAC counts are incrementing, observe the test light. Return engine idle speed to desired idle as indicated on the scan tool data list. Repeat the procedure for the other 3 IAC valve circuits. Did the test light remain ON, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the test? If yes, go to step  10. If no, go to next step.
  6. Did the test light remain OFF, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the test? If yes, go to step  9. If no, go to next step.
  7. Connect a test light between the IAC coil "A" low circuit and the IAC coil "A" high circuit at the IAC valve harness connector using the Connector Test Adapter Kit. With IAC Motor Driver, command low RPM while observing a scan tool until the IAC counts start to increment. With the IAC Motor Driver, command high RPM while observing a scan tool until the IAC counts start to increment. While the IAC counts are incrementing, observe the test light. Return engine idle speed to desired idle as indicated on scan tool data list. Repeat with test light connected between the IAC coil "B" low circuit and the IAC coil "B" high circuit at the IAC valve harness connector. Return engine speed to the desired idle as indicated on scan tool data list. Did the test light stay illuminated and never flashing while the IAC counts where incrementing during the test? If yes, go to next step. If no, go to step  16.
  8. Inspect for a poor connection at the IAC valve harness connector. Did you find and correct the condition? If yes, go to step  17. If no, go to step  12.
  9. Turn ignition off. Disconnect the PCM harness connectors. With a DVOM, test the circuit where the test light remained OFF for the following:
    • An open circuit.
    • A short to ground.
    • A short to another IAC valve circuit.

    After repairs, go to step  17.

  10. Turn ignition on. With DVOM, test the circuit where the test light remained ON for the following:
    • A short to voltage.
    • A short to another IAC valve circuit.

    Did you find and correct the condition? If yes, go to step  17. If no, go to step  12.

  11. Visually and physically inspect for the following:
    • Throttle body damage and tampering.
    • Throttle lever screw tampering, if equipped.
    • Restricted air intake system. Inspect for a possible collapsed/clogged air intake duct, before and after the air filter element, restricted air filter element, restriction at the throttle body intake screen, if equipped.

    Remove IAC valve. Inspect for the following conditions:

    • A clogged IAC passage.
    • Excessive deposits on the throttle plate.
    • Excessive deposits in the throttle bore.
    • Excessive deposits on IAC valve pintle.

    Repair any of the conditions as necessary. Did you find and correct the condition? If yes, go to step  17. If no, go to step  14.

  12. Inspect for a poor connection at the PCM harness connectors. Did you find and correct the condition? If yes, go to step  17. If no, go to next step.
  13. Disconnect the PCM harness connectors. With a DVOM, test all IAC valve circuits for high resistance. Did you find and correct the condition? If yes, go to step  17. If no, go to step  16.
  14. Inspect for a poor connection at the IAC valve harness connector. Did you find and correct the condition? If yes, go to step  17. If no, go to next step.
  15. Replace IAC valve. See REMOVAL & INSTALLATION - AZTEC & RENDEZVOUS article. After repairs, go to step  17.
  16. Replace PCM. See REMOVAL & INSTALLATION - AZTEC & RENDEZVOUS article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  17. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  18. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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