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Diagnostic Procedures

NOTE: For wiring diagrams, see WIRING DIAGRAMS .
  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK- ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.0L TRACKER article or DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.5L TRACKER article. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Is there a current or pending DTC P0506 or P0507 set? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.0L TRACKER article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.5L TRACKER article. If no, go to next step.
  3. Start and warm engine to normal operating temperature. Using scan tool, observe Engine Speed and IAC Motor Command parameters. Are the Engine Speed and IAC Motor Command within 700-800 RPM in Park or Neutral, or 650-750 RPM in Drive and 10-30% IAC Motor Command? If yes, go to step  5. If no, go to next step.
  4. Operate engine at normal operating temperature. Select RPM Control, under IAC System, in the Special Functions menu of the scan tool. Command IAC valve to increase and decrease engine speed with scan tool. Did engine speed increase and decrease as commanded by scan tool? If yes, go to next step. If no, go to step  8.
  5. Start engine. Place transmission in Park or Neutral. Operate the following accessories, one at a time, while observing the Engine Speed and IAC Motor Command parameters on scan tool: Turn on the headlights, HVAC blower motor with A/C off, and rear window defogger (if equipped). Does the engine speed stay within 700-800 RPM in Park or Neutral while the IAC Motor Command increases 2-3 percent? If yes, go to next step. If no, go to ACCESSORY/ELECTRICAL LOAD IDLE-UP SIGNAL DIAGNOSIS .
  6. Turn on the HVAC blower motor and A/C, if equipped. Is engine speed within 750-850 RPM range and does the IAC Motor Command increase 4-12 percent when A/C compressor is operating? If yes, go to next step. If no, go to ACCESSORY/ELECTRICAL LOAD IDLE-UP SIGNAL DIAGNOSIS .
  7. Turn off all accessories. Ensure that engine is operating at a normal temperature. Observe the Engine Speed and IAC Motor Command parameters on scan tool. Are the Engine Speed and IAC Motor Command within 700-800 RPM in Park or Neutral or 650-750 RPM in Drive and 10-30% IAC Motor Command? If yes, system is okay. If no, refer to ROUGH, UNSTABLE OR INCORRECT IDLE & STALLING under SYMPTOMS in TROUBLE SHOOTING - NO CODES - 2.0L & 2.5L TRACKER article.
  8. Turn ignition off. Disconnect IAC valve electrical connector. Using a DVOM, measure resistance of the following IAC valve coil windings between IAC valve terminals No. 1 and 2, terminals No. 2 and 3, terminals No. 5 and 6, and terminals No. 4 and 5. See Fig 1 or Fig 2 . Are the resistances within 35-43 ohms at 68°F (20°C)? If yes, go to next step. If no, go to step  15.
  9. Turn ignition on, with engine off. Probe both ignition positive voltage circuits of the IAC valve on the harness side with a test light connected to ground. Did test light illuminate on both circuits? If yes, go to next step. If no, go to step  12.
  10. Turn ignition off. Connect IAC valve electrical connector. Disconnect PCM electrical connector C4. Turn on, with engine off. Using a DVOM connected to ground, measure voltage of each IAC coil control circuit at the harness side of the PCM connector C4. Is voltage of each circuit more than 12 volts? If yes, go to next step. If no, go to step  13.
  11. Turn ignition off. Connect PCM electrical connector C4. Start engine. Warm engine to normal operating temperature. Using DVOM connected to ground, backprobe each IAC coil control circuit at the PCM. Observe voltage reading on DVOM each IAC coil control circuit while increasing and decreasing engine speed with scan tool RPM Control function. Does the voltage of circuit switch from high to low with the increase and decrease in engine speed? If yes, go to step  14. If no, go to step  16.
  12. Repair the high resistance or open in the ignition positive voltage circuit. After repairs, go to step  17.
  13. Repair short to ground, open circuit, or high resistance in any IAC coil control circuit that did not measure at least 12 volts in step  10. After repairs, go to step  17.
  14. Remove IAC valve. Inspect the idle air passage for restrictions or blockage. Repair as necessary. Was a repair necessary? If yes, go to step  17. If no, go to next step.
  15. Replace IAC valve. After replacing IAC valve, go to step  17.
  16. Replace PCM. See REMOVAL & INSTALLATION - TRACKER article. After repairs, go to next step.
  17. Operate vehicle within the conditions in which the customer concern was first noticed. Is the concern still present? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.0L TRACKER article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.5L TRACKER article. If no, system is okay.
Fig 1: Identifying Idle Air Control Valve Connector Terminals (2.0L)
G00117299Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying Idle Air Control Valve Connector Terminals (2.5L)
G00117342Courtesy of GENERAL MOTORS CORP.
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