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Home >> Chevrolet >> 2001 >> Tracker 2D Utility, 4WD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Engine Component Tests >> Idle Control System >> Idle Air Control System Diagnosis
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Idle Air Control System Diagnosis

  1. If powertrain diagnostic system check has been performed, go to next step. If powertrain diagnostic system check has been performed, perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
  2. If DTC P0505 is present or pending, see appropriate SELF-DIAGNOSTICS article. If DTC P0505 is not present or pending, go to next step.
  3. Start and warm engine to normal operating temperature. Using scan tool, observe IAC duty cycle. If IAC duty cycle is 10-30 percent at 700-800 RPM in Park or Neutral, go to step  5. If IAC duty is not 10-30 percent at 700-800 RPM in Park or Neutral, go to next step.
  4. Start and warm engine to normal operating temperature. Select RPM control, under IAC system, in SPECIAL FUNCTIONS menu of scan tool. Command IAC valve to increase and decrease engine RPM. If engine RPM increases and decreases as commanded, go to next step. If engine RPM does not increase or decrease as commanded, go to step  8
  5. Start engine. Place transmission in Park or Neutral. Operate headlights, HVAC blower motor (AC off) and rear window defogger (if equipped) one at a time, while observing engine RPM and IAC duty cycle on scan tool. If engine stays within 700-800 RPM and IAC duty cycle increases 2 to 3 percent, go to next step. If engine RPM and IAC duty cycle are not as specified, see ELECTRICAL/ACCESSORY LOAD IDLE-UP CIRCUIT DIAGNOSIS .
  6. Turn HVAC blower motor and AC on (if equipped). If engine RPM is 750-850 RPM and IAC duty cycle increases 4 to 12 percent, go to next step. If engine RPM and IAC duty cycle are not as specified, see ELECTRICAL/ACCESSORY LOAD IDLE-UP CIRCUIT DIAGNOSIS .
  7. Turn all accessories off. Ensure engine is at normal operating temperature. Using scan tool, observe engine RPM and IAC duty cycle. If engine RPM is 700-800 RPM and IAC duty cycle is 10-30 percent system is okay. If engine RPM and IAC duty cycle are not as specified, see TROUBLE SHOOTING - NO CODES article.
  8. Turn off ignition and disconnect IAC valve connector. On 2.0L models, measure resistance between the following IAC valve terminals. See WIRING DIAGRAMS article.
    • Terminals No. 1 (Purple/Black wire) and No. 2 (Blue/Black wire).
    • Terminals No. 3 (Light Green/Black wire) and No. 2 (Blue/Black wire).
    • Terminals No. 4 (Gray/Blue wire) and No. 5 (Blue/Black wire).
    • Terminals No. 6 (Purple/Yellow wire) and No. 5 (Blue/Black wire).

    If resistance is 35-43 ohms at 68°F (20°C), go to next step. If resistance is not 35-43 ohms, go to step  15.

    On 2.5L models, measure resistance between the following IAC valve terminals. See WIRING DIAGRAMS article.

    • Terminals No. 1 (Gray/Blue wire) and No. 2 (Blue/Black wire).
    • Terminals No. 3 (Light Green/Black wire) and No. 2 (Blue/Black wire).
    • Terminals No. 4 (Purple/Yellow wire) and No. 5 (Blue/Black wire).
    • Terminals No. 6 (Purple/Black wire) and No. 5 (Blue/Black wire).

    If resistance is 21-23 ohms at 68°F (20°C), go to next step. If resistance is not 21-23 ohms, go to step  15.

  9. Turn ignition on, engine off. Disconnect IAC valve connector. Using test light connected to ground, probe IAC valve connector (harness side) terminals No. 2 (Blue/Black wire) and No. 5 (Blue/Black wire). If test light illuminates on both circuits, go to next step. If test light does not illuminate on both circuits, go to step  12.
  10. Turn ignition off. Reconnect IAC valve connector. Disconnect PCM connector C4. Turn ignition on, engine off. On 2.0L models, measure voltage at PCM connector C4 terminals No. 3 (Light Green/Black wire), No. 10 (Purple/Yellow wire), No. 11 (Gray/Blue wire) and No. 12 (Purple/Black wire). On 2.5L models, measure voltage at PCM connector C4 terminals No. 14 (Purple/Black wire), No. 15 (Light Green/Black wire), No. 24 (Purple/Yellow wire) and No. 25 (Gray/Blue wire). If about battery voltage exists at all terminals, go to next step. If about battery voltage does not exist at all terminals, go to step  13.
  11. Turn ignition off. Reconnect PCM connector C4. Start and warm engine to normal operating temperature. On 2.0L models, using DVOM connected to ground, backprobe PCM connector C4 terminals No. 3 (Light Green/Black wire), No. 10 (Purple/Yellow wire), No. 11 (Gray/Blue wire) and No. 12 (Purple/Black wire) and on 2.5L models, measure voltage at PCM connector C4 terminals No. 14 (Purple/Black wire), No. 15 (Light Green/Black wire), No. 24 (Purple/Yellow wire) and No. 25 (Gray/Blue wire). Observe voltage display on DVOM for each IAC coil control circuit while increasing and decreasing engine RPM with scan tool RPM control function. If voltage of each circuit changes from high to low with increase and decrease in engine RPM, go to step  14. If voltage of each circuit does not change from high to low with increase and decrease in engine RPM, go to step  16.
  12. Repair high resistance or open in ignition voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step  17.
  13. Repair open, short to ground or high resistance in any IAC coil control circuit that did not measure battery voltage. After repairs, go to step  17.
  14. Remove IAC valve. Inspect idle air passage for restrictions or blockage. Repair as necessary. After repairs, go to step  17. If idle air passages are not restricted, go to next step.
  15. Replace IAC valve. After repairs, go to step  17.
  16. Replace PCM. After repairs, go to next step.
  17. Operate vehicle within conditions under which original symptom was observed. Using scan tool, retrieve DTCs. If no DTCs are set, system is okay. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
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