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Home › Chevrolet › 2001 › Metro › Repair and Diagnosis › Engine Performance › System › Engine Controls Self-Diagnostics - 1.3L › Diagnostic Tests › DTC P0505: Idle Control System › 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. Start and warm engine to normal operating temperature. Turn off all electrical accessories. Using scan tool, monitor IAC duty cycle parameter. If scan tool indicates IAC duty cycle is 8-25 percent, see DIAGNOSTIC AIDS . Check for an intermittent problem. If scan tool does not indicate IAC duty cycle is 8-25 percent, go to next step.
  3. Check for vacuum leaks, incorrectly routed vacuum lines and hoses, split or damaged vacuum lines and hoses, blocked inlet air ducts and passages, and plugged air filter element. Repair as necessary. After repairs, go to step  14. If no problem is found, go to next step.
  4. Turn ignition off. Disconnect IAC valve harness connector. Turn ignition on, with engine off. Using test light connected to ground, probe IAC valve harness connector terminal No. 2 (White/Blue wire). See Figure. If test light illuminates, go to next step. If test light does not illuminate, go to step  6.
  5. Using DVOM, check voltage in IAC valve harness connector terminal No. 2 (White/Blue wire). If battery voltage is present, go to step  7. If battery voltage is not present, go to next step.
  6. Turn ignition off. Repair open or short in White/Blue wire between IAC valve harness connector terminal No. 2 and main relay (located in relay block, in left side of engine compartment). After repairs, go to step  14.
  7. Using test light connected to battery voltage, probe IAC valve harness connector terminal No. 3 (Black/Blue wire). If test light illuminates, go to step  9. If test light does not illuminate, go to next step.
  8. Turn ignition off. Repair open in Black/Blue wire between IAC valve harness connector terminal No. 3 and ground connection. After repairs, go to step  14.
  9. Turn ignition off. Reconnect IAC valve harness connector. Disconnect PCM harness connector C3. Back out PCM harness connector C3 terminal No. 2 (Red/Yellow wire). See Figure. Reconnect PCM harness connector with IAC valve control circuit terminal removed. Turn ignition on, with engine off. Using DVOM, probe PCM harness connector terminal No. 2. If battery voltage is present, go to next step. If battery voltage is not present, go to step  11.
  10. Start engine. Using scan tool, monitor engine speed parameter. Using test light connected to ground, momentarily probe PCM harness connector C3 terminal No. 2 (Red/Yellow wire). If engine speed increases when test light contacts IAC valve control circuit, go to step  13. If engine speed does not increase when test light contacts IAC valve control circuit, go to step  12.
  11. Turn ignition off. Check for open or short in Red/Yellow wire between IAC valve harness connector terminal No. 1 and PCM harness connector C3 terminal No. 2. Repair as necessary. After repairs, go to step  14. If circuit is okay, go to next step.
  12. Turn ignition off. Replace IAC valve. After replacing IAC valve, go to step  14.
  13. Turn ignition off. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  14. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within FREEZE FRAME/FAILURE RECORDS data conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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