P0511: Idle Air Control Circuit
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes, but expect stalling at stops and a wandering idle.
Symptoms
- Idle surging up and down
- Stalling when coming to a stop
- High idle with no load
- Hard starting unless the throttle is pressed
Likely causes, most common first
- Idle air control valve carboned up or failed
- IAC circuit open or shorted
- Connector fault
- Vacuum leak mimicking an idle control problem
Read P0511 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0511 is the idle air control circuit - the small stepper valve that meters air around a closed throttle on cable-throttle engines. This code lives mostly on vehicles from the 1990s and 2000s; electronic throttles made the part obsolete, so it marks the car's generation as surely as its symptoms do.
Decades of crankcase vapors coke the valve's passages until the pintle sticks, and cleaning with throttle body cleaner genuinely fixes a large share of them - one of the few codes where a twenty-dollar aerosol can is a legitimate repair. If the circuit itself tests bad rather than the valve sticking, the usual suspects are the connector and the harness section that flexes with the engine.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Frequently asked questions
Can I drive with P0511?
Yes, but expect stalling at stops and a wandering idle.
How much does it cost to fix P0511?
Typical US repair costs range from $60 for the simplest fix (iac valve cleaning) to $450 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0511. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.