Normal Operation
WARNING: This page is about a different car, the 2013 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
The cruise control switches uses the PCM RUN/START voltage and the PCM ground. The cruise control functionality is controlled through the cruise control switches and is hardwired to the PCM through a signal and return circuit.
There are 5 cruise control switches with each switch operating a specific function that uses different resistance values. The PCM sends out a reference voltage to the cruise control switches and monitors the voltage drop when a cruise control switch is pressed. The voltage drop varies depending upon the resistance of each switch, providing a specific indication to the PCM which switch is pressed, activating and controlling the cruise control system.
- DTC P0579 (Cruise Control Multifunction Input A Circuit Range/Performance) - sets when the cruise control switch circuits are open, shorted to voltage or ground.
- DTC P0581 (Cruise Control Multifunction Input A Circuit High) - sets when the cruise control switch circuits are shorted to voltage or open.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Clockspring
- Cruise control switches
- PCM