The computer cannot control idle speed as expected. The driver may notice high, low or surging idle, or stalling.
Likely causes, most common first
- Dirty throttle body or idle valve
- Vacuum leak
- Faulty idle air control valve
- Wiring fault
Parts usually involved
- Idle air control valve
- Throttle body
- Intake gaskets
Test before you replace
Clean and inspect the idle air path, check for vacuum leaks and test the valve or throttle control.
General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.