Common Checks
- Inspect the IAC connector, vacuum leaks, throttle body deposits, and base idle condition.
- Check for intake leaks before replacing the IAC valve.
- Confirm the throttle blade and cable are not sticking.
Diagnostic trouble code
P0505 Idle Air Control System
The PCM cannot control idle speed with the idle-air-control system.
Throttle & Idle Control CodesCommon Repairs
- Clean throttle-body deposits and repair vacuum leaks.
- Replace a failed IAC valve after confirming power, ground, and command.
- Repair wiring or connector faults.
Mustang Notes
- Cable-throttle SN95 and New Edge cars are the main Mustang years for this fault.
Model-Year Applicability
Listed for 1996-2004 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.