Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P0511 Idle Air Control Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

CARB requires the idle speed control to be monitored: petrol engines must flag a fault if the target idle speed is not reached within +200/−100 rpm, diesels within ±30 %. Older engines use a separate idle air control valve that bypasses the closed throttle; with electronic throttle the throttle itself controls idle and no separate valve exists. P0511 is the general circuit fault of the idle valve – open, short to ground or to positive – without separating low and high, which CARB permits. Ford (up to about 2012, engines with an idle valve) has the output stage report it via a diagnostic status bit, continuously. Valve types are PWM solenoid or rotary valves (two wires) or stepper motors (four wires, typical of GM). Without a working valve the engine runs on a fixed bypass or the mechanical stop and may stall.

Likely causes

Idle valve faulty (coil open or shorted)
Wire open or shorted
Connector corroded, pins pushed back
Driver in the engine module

Symptoms

  • Idle too high, too low or fluctuating
  • Engine stalls at idle
  • Check engine light on

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–350
Time0.5–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

idle air control valvevalve wiringengine control module

Related codes

P0508P0509P0505P0506P0507

References: newtonnet.co.uk, docs.hptuners.com, hella.com, law.cornell.edu.