DTC P0505: Idle Control System Malfunction

NOTE: If DTC P1508 is also set, trouble shoot that DTC before DTC P0505.

If DTC P0505 is set, check for:
- IAC valve mechanical malfunction.
- Throttle body clogged port or is improperly adjusted.
- Intake manifold gasket leakage.
- Intake air hose loose or leaking.
- Vacuum hose leakage.
- ECT sensor incorrect output.
- TP sensor incorrect output.
Repair as necessary. If no problems are found, go to next step.
Start engine and hold at 3000 RPM with no load 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). 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).
Disconnect Idle Air Control (IAC) valve 3-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 ADJUSTMENTS article. If engine speed does not adjust to specification, clean throttle body and ports.
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, check for vacuum leaks. Ensure throttle valve is completely closed and repair as necessary. If engine speed drops, adjust idle speed. If idle is not adjustable, replace IAC valve.