Common Checks
- Inspect for dirty throttle body, vacuum leaks, and accessory load issues.
- Check electronic-throttle data on newer cars.
- Look for companion throttle or airflow codes.
Diagnostic trouble code
P0506 Idle Air Control System RPM Lower Than Expected
Idle speed is lower than the PCM expects.
Throttle & Idle Control CodesCommon Repairs
- Clean the throttle body using the correct procedure for the throttle type.
- Repair vacuum leaks or throttle-control faults.
- Perform required idle relearn steps after service where applicable.
Mustang Notes
- Modern electronic-throttle cars can need idle relearn after battery or throttle service.
Model-Year Applicability
Listed for 1996 and newer traditional gasoline Mustang pages in this first-pass catalog. Engine, calibration, and Ford-specific codes may narrow that range as more service data is added.