Powertrain
generic / SAE
P0509
Idle Air Control System Circuit High
Same as P0508 with the line shorted to supply or open. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number5 / 09
Possible causes
- Control line shorted to supply high
- Open in IAC valve or harness medium
- Connector pins corroded - high contact resistance low
Symptoms
- Check engine light on
- Idle speed too high, too low, or unstable
- Possible stalling at idle or after cold start
Inspection / repair
- Difficulty: easy
- DIY: possible
- Estimated cost: 80–320 €
- Estimated time: 0.4–1.5 h
- Component: idle air control valve
- Component: iac wiring
- MIL / check engine light
Sources
References
sae:J2012