Diagnostic Overview
Meaning: Fault code P0505 indicates that your vehicle's Engine Control Module (ECM/PCM) has registered a threshold discrepancy for idle control system malfunction.
Can I Drive With This Code? Yes, you can safely drive for short distances, but prompt diagnostic inspection is recommended to prevent secondary damage or reduced engine performance.
What does the P0505 code mean?
Diagnostic Trouble Code (DTC) P0505 is defined as Idle Control System Malfunction. This trouble code is logged when the onboard computer detects operational values outside calibrated thresholds.
When stored, the system illuminates the Check Engine Light (MIL) to alert the driver of an active fault condition.
Common Symptoms of Code P0505
Depending on vehicle model and operating conditions, symptoms may include:
- Check Engine Light on
- Very high engine idle speed (1200+ RPM)
- Engine stalls at idle or when clutching in
- Fluctuating idle speed (surging)
Common Potential Causes for Code P0505
Common causes for P0505 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
Inspection Checklist
Recommended diagnostic procedures:
- Step 1: Check idle speed in OBDAssistant. Compare commanded vs actual idle RPM.
- Step 2: Remove and inspect IAC valve. Clean with throttle body cleaner.
- Step 3: Check for vacuum leaks at intake gaskets or hoses.
Symptoms that lead to P0505
If you have not scanned the car yet, or P0505 is one of several codes stored, these guides start from what the vehicle is actually doing.