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DTC P0505: Idle Control System Malfunction

NOTE: If DTC P1508  is also set, trouble shoot that DTC before DTC P0505.
  1. Start engine and hold at 3000 RPM with no loads and transmission in Park or Neutral, until cooling fan comes on. Let engine idle. Using scan tool, ensure throttle position is about 10 percent with throttle fully closed and engine coolant temperature is 194-205°F (90-96°C). If throttle position and engine coolant temperature are within specification, go to next step. If throttle position or engine coolant temperature are not within specification, repair faulty sensor circuit.
  2. Using scan tool, check engine speed at idle with no loads (headlights, blower motor, rear defogger, radiator cooling fan, and A/C are all off). If idle speed is 650-750 RPM, problem is intermittent, system is okay at this time. If idle speed is 650 RPM or less, go to next step. If idle speed is not 650 RPM or less, go to step 4).
  3. Disconnect Idle Air Control (IAC) valve 2-pin connector. If engine speed does not drop or engine does not stall, replace IAC valve. If engine speed drops or engine stalls, adjust base idle speed. See the ADJUSTMENTS article. If engine speed does not adjust to specification, clean throttle body and ports.
  4. Turn ignition off. Remove intake air duct from throttle body. Start engine and let idle. Place your finger over lower port located in throat of throttle body. If engine speed does not drop, go to next step. If engine speed drops, check engine coolant level and for air in cooling system. If cooling system is okay, replace fast idle thermo valve.
  5. Place your finger over upper port located in throat of throttle body. If engine speed does not drop, check for vacuum leaks. Ensure throttle valve is fully closed. Repair as necessary. If engine speed drops, adjust base idle speed. See the ADJUSTMENTS article. If base idle speed can not be adjusted to specification, replace IAC valve.
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