P0511: Idle Air Control Circuit
What to do
Usually driveable with an unstable or hunting idle.
What this code means
A general circuit fault on the idle air control valve, raised where the module can tell the circuit is wrong without resolving it into a high or low reading. Intermittent connections account for most of these.
On a stepper-motor idle valve there are four windings rather than one, and a single failed winding produces exactly this — the valve still moves, but not through its full range. Measuring each winding pair separately is what finds it.
Likely causes
Start here
- Faulty idle air control valve · moderate
- Corroded or loose connector · easy
- Open or shorted solenoid winding · easy
Less common
- Intermittent open in sensor wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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