What P0505 means
Diagnostic Trouble Code (DTC) P0505 stands for Idle Control System Malfunction. This is a generic OBD2 diagnostic trouble code indicating that the engine computer (ECU) has registered an operational anomaly in the powertrain (p) systems.
When this error registers, the ECU records a freeze frame of sensor data and lights up the Check Engine Light on your dashboard to notify the operator of a system fault.
Symptoms of OBD2 Code P0505
When code P0505 is active, your car might exhibit the following common symptoms:
- Check Engine Light on
- Very high engine idle speed (1200+ RPM)
- Engine stalls at idle or when clutching in
- Fluctuating idle speed (surging)
Common Causes of Code P0505
Faults that trigger this code typically include:
- Cause 1: Faulty Idle Air Control (IAC) valve
- Cause 2: Heavy carbon deposits inside the IAC valve passages or throttle body
- Cause 3: Large vacuum leak behind the throttle body
- Cause 4: IAC electrical wiring connector corroded
Can you drive with a P0505 code?
Yes, but the engine may idle excessively high (wasting fuel and heating transmission) or stall constantly at stoplights.
Expected Repair Cost Band
Cleaning IAC/throttle body ($15 DIY spray). IAC valve replacement ($120 - $350).
Related Diagnostic Trouble Codes
If you have scanned multiple codes, see these related guides for troubleshooting context:
Frequently Asked Questions
The Idle Air Control valve regulates how much air bypasses the closed throttle plate to keep the engine running smoothly at idle.