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.
Affected components
- Idle air control valve
- Iac wiring
Common causes
- High likelihood: Control line shorted to supply
- Medium likelihood: Open in IAC valve or harness
- Low likelihood: Connector pins corroded - high contact resistance
Possible symptoms
- Check engine light on
- Idle speed too high, too low, or unstable
- Possible stalling at idle or after cold start
Diagnostic notes
- The malfunction indicator lamp may illuminate
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.