P0507
Idle Air Control System RPM Higher Than Expected
Idle RPM exceeds the target despite the IAC commanded fully closed. Almost always caused by a vacuum leak that lets air bypass the IAC — torn intake hose, leaking PCV, brake booster, or intake manifold gasket.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Idle speed too high, too low, or unstable
- Possible stalling at idle or after cold start
Common causes
Ordered by how often each turns out to be the cause.
- Vacuum leak bypassing IACCommon
- PCV valve stuck openPossible
- Brake booster diaphragm leakingPossible
Parts involved
- Intake Manifold
- PCV Valve
- Brake Booster
- Vacuum Hose
P0507 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.