P1504
PPowertrainIdle Air Control (IAC) Circuit Fault
What does this code mean?
Severity : MediumP1504 reports an idle air control (IAC) circuit malfunction. This valve lets a controlled amount of air bypass the throttle to keep idle speed steady. The module detects an electrical problem in its circuit. This is a manufacturer-specific code: the exact meaning depends on the manufacturer.
Symptoms
- Check engine light on.
- High, low or unstable idle.
- Stalling at stop or when decelerating.
- Hard start.
Possible causes
- Dirty or faulty idle air control valve.
- Corroded or loose connector.
- Wire open or shorted.
- Intake air leak disturbing idle control.
- Faulty control module, less often.
Diagnosis and repair
- Inspect the idle air control valve connector and wiring.
- Measure the valve resistance with a multimeter.
- Clean the valve and its air passage if dirty.
- Replace the valve if it stays out of specification.
- Clear the code, let idle relearn and road test.
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Code
P1504
Category
Powertrain
Prefix
P
Standard
OBD-II / SAE J2012