P0518
Idle Air Control Circuit Intermittent
Idle air control
Generic OBD-II
High
What it means
P0518 means the idle air control (IAC) circuit is dropping out or reading erratically. The IAC valve meters air around the throttle plate to hold a steady idle, so an intermittent fault shows up as rough idle, surging, or stalling — often when cold or coming to a stop. It's usually a wiring/connector problem or a carbon-fouled IAC valve.
High
Can I keep driving? Drivable but annoying — the engine may idle roughly or stall, especially when cold or coming to a stop, so keep restarts easy and get it fixed soon.
Common symptoms
What you'll notice
- Rough, unstable, or surging idle
- Engine stalling at stops or when cold
- Higher-than-normal or hunting idle speed
- Check-engine light on
Common causes
Most likely first
- Intermittent open, short, or chafed wiring in the idle air control (IAC) circuitLikely
- Loose or corroded IAC connectorCommon
- Faulty or carbon-fouled IAC valveCommon
- Carbon buildup in the throttle body/idle passagesLess often
- Rarely, a failed ECM driverLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and watch idle speed and IAC counts on a scan tool for dropouts.
- Wiggle-test the IAC connector and harness to reproduce the intermittent fault.
- Inspect the connector for corrosion and the wiring for chafing or shorts.
- Remove and clean the IAC valve and throttle body of carbon buildup.
- Replace the IAC valve if it's faulty. Clear and re-test idle stability.
FAQ
Quick answers
Is it safe to drive with P0518?+
Generally yes, but stalling at stops can be inconvenient and unsafe in traffic. Fix it soon, especially if the engine dies when coming to a stop.
Can I just clear P0518?+
You can, but as an intermittent fault it will return when the wiring or IAC valve acts up again. Repair the circuit or valve to keep it away.
Related codes
Often seen with P0518
Read & clear P0518 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX