Trouble code
P0505
Idle Air Control System Malfunction
What P0505 means
The computer cannot hold the commanded idle speed through the idle air control system.
Symptoms you may notice
- Idle too high or too low
- Stalling at stops
- Surging idle
Common causes, cheapest first
- Carbon buildup in the idle air control valve or throttle body
- Failed IAC valve
- Vacuum leak
- Dirty throttle plate
Before you buy anythingClean the throttle body and the IAC passage first. This code is caused by carbon far more often than by a failed part.
What to do next
- Confirm the code with your own scan tool, or have it read free at a chain parts store.
- Decode your VIN so you know your exact engine and build date.
- Work down the causes above from cheapest to most expensive.
- Search NHTSA for a recall or service bulletin covering this symptom on your vehicle.
- Read the engine buying guide before ordering.
P0505 is a generic OBD-II code, standardized across every make and model sold in the US from 1996 onward. The meaning is the same on any vehicle; the specific part and its location are not.
Parts
Parts commonly needed for P0505
These go to Amazon. We earn a commission if you buy, at no extra cost to you — see our affiliate disclosure. Which one you actually need depends on diagnosis — read the note above first.
Confirm fitment against your VIN on the listing page before ordering. A part that matches your year and model can still be wrong for your build date or engine code.