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Home >> Chevrolet >> 2000 >> Tracker 4D Utility, RWD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0505: Idle Control System >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Check for stuck or binding throttle valve, accelerator cable, or accelerator pedal. Check for vacuum or intake air leaks. Check for EGR or EVAP system malfunction. Check for faulty or Incorrect TP sensor, ECT sensor, or MAF sensor input. Repair as necessary. After repairs, go to step  55. If no problems were found, go to next step.
  3. Turn ignition on, with engine off. Using scan tool, clear DTCs. Start and operate engine for one minute. Recheck for DTCs. If a current or pending DTC P0505 is set, go to step  7. If no current or pending DTC is set, go to next step.
  4. Warm engine to normal operating temperature. Using scan tool, select RPM CONTROL under IAC system in Special Functions menu. Command IAC valve to increase and decrease engine speed. If engine speed increases and decreases when commanded by scan tool, go to next step. If engine speed does not increase or decrease when commanded by scan tool, go to step  7.
  5. Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions or until DTC P0505 diagnostic test has run. If DTC P0505 resets, go to step 7. If DTC P0505 does not reset, go to next step.
  6. Start engine. Turn off all accessories. Warm engine to normal operating temperature. Observe the engine speed and IAC duty cycle parameters on scan tool. If engine speed is within 700-800 RPM in Park or Neutral, and IAC duty cycle is at 10-30 percent, system is okay. If engine speed is not within 700-800 RPM in Park or Neutral, and IAC duty cycle is not at 10-30 percent, diagnose idle problem. See SYMPTOMS (GASOLINE) in appropriate TROUBLE SHOOTING - NO CODES article.
  7. Turn ignition off. Disconnect IAC valve harness connector. Turn ignition on, with engine off. Using a test light connected to ground, probe both IAC valve ignition positive voltage circuits (harness side). If test light illuminated on both circuits, go to next step. If test light did not illuminate on both circuits, go to step  11.
  8. Disconnect IAC valve harness connector. Using DVOM, check resistance of IAC valve coil windings. Check between terminals No. 1 and 2, terminals No. 2 and 3, terminals No. 5 and 6, and terminals No. 4 and 5. If resistance is 35-43 ohms at 68°F (20°C), go to next step. If resistance is not 35-43 ohms at 68°F (20°C), go to step  14.
  9. Turn ignition off. Reconnect IAC valve harness connector. Disconnect PCM harness connector. Turn ignition on, with engine off. Check voltage of each IAC coil control circuits at PCM harness connector. If voltage reading of each IAC coil control circuit is greater than 12 volts, go to next step. If voltage reading of each IAC coil control circuit is not greater than 12 volts, go to step  12.
  10. Turn ignition on. Reconnect PCM harness connector. Start and warm engine to normal operating temperature. Using a DVOM connected to ground, backprobe each IAC coil control circuit at PCM harness connector. Observe voltage display on DVOM for each IAC coil control circuit while increasing and decreasing engine speed with scan tool in RPM Control function. If voltage of each IAC coil control circuit is switching from high to low while increasing and decreasing the engine speed, go to next step. If voltage of each IAC coil control circuit is not switching from high to low while increasing and decreasing the engine speed, go to step  15.
  11. Repair high resistance or open in ignition positive voltage circuit. After repairs, go to step  16.
  12. Repair short to ground, open circuit, or high resistance in any IAC coil control circuit that did not measure at least 12 volts. After repairs, go to step  16.
  13. Remove IAC valve. Check idle air bypass passage for restrictions or blockage. After repairs, go to step  16. If passages are okay, go to next step.
  14. Replace IAC valve. After replacing IAC valve, go to step  16.
  15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  16. After repairs, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).
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