Parts
$30–100
P0511 — Idle Air Control Circuit
CAUTIONIs it safe to drive? Electrical fault in the IAC circuit — may cause stalling or rough idle; drivable but the stall risk at stops makes this worth addressing soon.
What P0511 means
The ECM commanded the idle air control valve and didn't get the expected circuit response. This is an electrical code — the valve solenoid coil, its wiring, or the connector has an open or short, separate from the IAC being mechanically gummed up.
Most likely causes (in order)
- IAC valve solenoid coil failed (measure resistance — typically 7–15 ohms)
- Connector corroded or broken pin
- Wiring harness chafed or open between ECM and IAC
- Ground path for IAC circuit poor
- ECM driver for IAC circuit failed (rare)
Symptoms you might notice
- rough or erratic idle
- stalling at idle
- idle speed too high or too low
- CEL on
What to check first
Measure IAC solenoid coil resistance at the valve connector — most 2-wire IAC valves read 7–15 ohms; a 3-wire stepper motor IAC has multiple coil pairs. An open reading confirms a failed coil; correct resistance means trace the wiring back toward the ECM for the fault.
Repair cost & difficulty
Labor
0.5–1.5 hr
Difficulty
DIY-friendly