P0509: Idle Air Control System Circuit High
What to do
Usually driveable with an unstable idle.
What this code means
The idle air control circuit is reading high — an open circuit, or a control wire that has found a supply voltage. The mirror of the circuit-low fault and diagnosed identically: isolate the valve and re-measure to establish which side of the connector the fault lies on.
Likely causes
Start here
- Open or shorted solenoid winding · easy
- Broken wire in control circuit · moderate
- Faulty idle air control valve · moderate
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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