P0511

Idle Air Control Circuit

Vehicle speed & idle control Generic OBD-II High

What it means

P0511 means the ECM has detected an electrical fault in the idle air control (IAC) circuit. The IAC valve meters air around the throttle plate to hold a steady idle. When its circuit fails, idle can run high, low, surge, or stall — and the engine may be hard to start. It's usually the IAC valve, its wiring, or carbon buildup; because stalling at stops is possible, treat it as a priority repair.

High

Can I keep driving? Maybe, but unreliably — the idle can surge, drop, or stall, so short careful trips only; a car that stalls at stops is a safety concern until fixed.

Real-world scan data

Seen in

510

scans in the past year

Found in

0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of P0511 scans

P0443in 55.1% of scans

P0351in 28.0% of scans

P0335in 25.9% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Idle too high, too low, or surging
Rough idle or stalling, especially at stops or when cold
Hard starting or needing throttle to keep it running
Check-engine light on

Common causes

Most likely first

Faulty idle air control (IAC) valveLikely
Open or short in the IAC circuit wiringCommon
Corroded or loose IAC connectorCommon
Carbon buildup in the IAC valve or throttle body/idle passageLess often
Faulty ECM/PCM (rare)Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data and note when the idle problem occurs (cold, warm, at stops).
Inspect the IAC valve connector and wiring for opens, shorts, and corrosion.
Remove and inspect the IAC valve; clean carbon from the valve and idle air passage.
Test the IAC valve's resistance/operation against spec; replace it if faulty.
If the valve and circuit are good, suspect the ECM driver. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0511?+

Use caution — the engine can stall at idle or stops, which is a safety risk. Keep trips short until the IAC circuit is repaired.

Can I just clear P0511?+

You can, but the idle problem and code return until the IAC valve or its wiring is repaired.

Read & clear P0511 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX