P0511 Idle Air Control Circuit Malfunction

P0511 indicates an idle air control circuit malfunction. The controller has detected a general electrical or functional problem in the idle air control path.

Code details

Generic OBD-II · P0

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace idle control hardware until vacuum leaks, throttle deposits, wiring, and actuator response are tested.

Symptoms of P0511

Unstable, high, or low idle, or stalling.
Erratic speedometer, cruise-control, or shift behaviour.
Check-engine light with a hesitation or surge.

Common causes of P0511

A dirty throttle body, idle-control valve, or throttle-position sensor.
A failing vehicle-speed or wheel-speed sensor, or its wiring.
Vacuum leaks or a related sensor forcing the idle/speed strategy.

Useful checks before replacing parts

Check IAC command, actual idle speed, control voltage, current draw, throttle position, intake airflow, fuel trims, and freeze-frame idle data.
Inspect IAC wiring, connector terminals, actuator movement, carbon deposits, vacuum leaks, PCV faults, throttle body condition, and grounds.
Command idle control and confirm whether actuator movement produces a predictable idle speed change.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.