P0511: Idle Air Control Circuit

What does P0511 mean?

The idle-air-control circuit is malfunctioning. On engines fitted with an IAC valve or motor, the computer uses it to meter bypass air at idle; not every electronic-throttle engine has a separate IAC part.

Generic OBD-II definition: Idle Air Control Circuit. Confirm applicability in your vehicle service information.

Common causes

• Failed IAC valve or motor
• Open or shorted IAC harness
• Carbon buildup or a vacuum leak affecting control

Symptoms

• Unstable idle
• Stalling at stops
• Idle too high or too low

Diagnostic focus

This is a circuit code, unlike P0506 or P0507 which describe actual idle speed. Cleaning the throttle may help airflow but does not repair a failed IAC winding.

Can I keep driving with P0511?

Severity: Medium Arrange prompt diagnosis. Do not continue driving if the engine stalls at stops or cannot hold a safe idle.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Confirm the engine uses a separate IAC device
• Inspect wiring and test the actuator circuit
• Check bypass passages and vacuum leaks after the electrical tests

Sources & review

• OBD-Codes.com: P0511
• TroubleCodes.net: generic code definitions

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.