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Home >> Chevrolet >> 2000 >> Tracker 4D Utility, 4WD, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Engine Component Tests >> Idle Control System >> Idle Air Control (IAC) System Diagnosis
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Idle Air Control (IAC) System Diagnosis

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. Go to next step.
  2. Start and warm engine to normal operating temperature. Using scan tool, observe IAC duty. If IAC duty is 10-30 percent at 700-800 RPM go to  6 . If IAC duty is not 10-30 percent at 700-800 RPM, go to next step.
  3. Turn off ignition and disconnect IAC valve connector. Using DVOM, measure resistance between the following IAC valve terminals. See appropriate wiring diagram in 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, replace IAC valve.

  4. With engine idling at normal operating temperature, turn A/C on. Using scan tool, observe IAC duty cycle. If IAC duty is 4-12 percent higher and engine speed is 800-900 RPM, go to next step. If IAC duty cycle or engine speed is not as specified, diagnose A/C idle circuit. See A/C IDLE CIRCUIT DIAGNOSIS  .
  5. With engine idling at normal operating temperature, using scan tool, observe MAF sensor, HO2S and TP sensor operation. If sensors are within proper operating range, go to next step. If sensors are not within proper operating range, diagnose sensor. See appropriate sensor under ENGINE SENSORS & SWITCHES  .
  6. With engine idling at normal operating temperature, place transmission in Reverse or Drive. Using scan tool, observe IAC duty. If IAC duty increases, go to next step. If IAC duty does not increase as specified, diagnose transmission range switch. See TRANSMISSION RANGE SWITCH  under ENGINE SENSORS & SWITCHES.
  7. With engine idling at normal operating temperature, turn steering wheel to the left, and then to the right for more than one turn. If engine RPM changes, go to next step. If engine RPM does not change, diagnose Power Steering Pressure (PSP) switch. See POWER STEERING PRESSURE SWITCH CIRCUIT DIAGNOSIS  under MISCELLANEOUS CONTROLS.
  8. Check Positive Crankcase Ventilation (PCV) system. See POSITIVE CRANKCASE VENTILATION  under EMISSION SYSTEMS & SUB-SYSTEMS. Repair as necessary. If PCV system is okay, go to next step.
  9. 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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