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Home >> Chevrolet >> 1998 >> Tracker 4D Utility, RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0505: Idle Control System >> Diagnostic Test

Diagnostic Test

  1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK  .
  2. Connect scan tool to data link connector. Start engine. Warm engine to normal operating temperature. Check Idle Air Control (IAC) flow duty parameter on scan tool. If IAC flow duty is not 20-60 percent, go to next step. If IAC flow duty is 20-60 percent, go to step 4).
  3. Check for proper idle speed. If idle speed is incorrect, adjust as necessary and go to step 2). If idle speed is correct, go to step 5).
  4. Turn engine off. Turn ignition switch to RUN position. Use scan tool to clear information function. Operate vehicle within freeze frame conditions. If DTC P0505 is set, go to next step. If DTC P0505 is not set, check the following and repair as necessary:
    • Idle speed.
    • Restricted air intake system.
    • Throttle body for excessive carbon deposits in IAC air passage and throttle bore.
    • Malfunctioning power steering pressure switch circuit.
    • Malfunctioning A/C idle circuit.
    • Connection at PCM and IAC valve.
    • Damaged wiring harness.
  5. Turn ignition switch to LOCK position. Disconnect IAC valve harness connector. Using a test light connected to ground, probe IAC valve ignition feed circuit (Blue/Black wire) at IAC valve harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
  6. Measure resistance between IAC valve terminals. If resistance is 11-14 ohms at 68°F (20°C), go to next step. If resistance is not 11-14 ohms at 68°F (20°C), go to step 10).
  7. Disconnect air intake hose from top of IAC valve. Blow air into air intake port of IAC valve. Air should not pass through IAC valve. Apply battery voltage to terminal No. 2 at IAC valve. Ground terminal No. 1 at IAC valve. Air should now pass through IAC valve. If IAC valve operates as described, go to next step. If IAC valve does not operate as specified, go to step 10).
  8. Check IAC valve control circuit (Green/Black wire) for an open, between the PCM and the IAC valve harness connectors. If open does not exist, go to step 11). If open exists, repair as necessary and go to step 12).
  9. Check IAC valve ignition feed circuit (Blue/Black wire) for an open or short, between main relay and IAC valve harness connectors. If open or short does not exist, repair main relay circuit as necessary. If open or short exists, repair as necessary and go to step 12).
  10. Replace IAC valve and go to step 12).
  11. Replace PCM and go to next step.
  12. Test drive vehicle under conditions that set the DTC. Check for other DTCs. If DTCs were retrieved, perform appropriate DTC test. If no DTCs were retrieved, system is okay at this time.
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