P0505: Idle air control system malfunction
Drive carefully. Get it checked within a week or two.
Can I drive with P0505?
Yes, but drive carefully and get it checked soon. Engine may stall at stoplights or idle erratically between high and low revs.
What does P0505 mean?
P0505 stands for Idle Air Control System Malfunction.
Symptoms you may notice
- Engine stalls when coming to a stop or shifting into reverse
- Engine idles excessively high (over 1200 RPM) or surges up and down
- Heavy vibration through the steering wheel at idle
How much does it cost to fix?
Repair costs for code P0505 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:
- Carbon buildup in Idle Air Control (IAC) valve
- Failed IAC stepper motor
- Large intake vacuum leak
- Dirty throttle body bore and plate
What to do next
- Clean carbon buildup from the IAC valve and throttle body using throttle body cleaner.
- Check for cracked vacuum lines around the intake plenum.
- Replace the IAC valve if cleaning does not restore steady idle.
Last updated: October 2026
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General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.
About this code
Code P0505 indicates that the engine idle speed cannot be maintained by the idle air control system. The engine may stall whenever you let off the gas at intersections or surge erratically in parking lots. You can keep two feet on the pedals to prevent stalling on your drive home, but service is needed soon.