Switch, Speed Control: Operation: Operation
The speed control switch is a resistor multiplexed unit that provides hard wired inputs to the Powertrain Control Module (PCM) microprocessor. The speed control switch receives source current and provides hard wired analog outputs to the PCM through the steering wheel wire harness connection to the vehicle electrical system.
The speed control switch stalk and push button for vehicles equipped with the electronic speed control system provides four switch functions:
- Cruise On/Off - Depressing and releasing the switch push button on the end of the control stalk enables or disables the speed control system and clears any previous speed control set speed from system memory.
- Resume / Accel - Lifting the switch stalk upward (in the same plane as steering wheel rotation) restores the vehicle to a previously stored set speed or accelerates the vehicle from an already attained set speed.
- Cancel - Lifting the switch stalk toward you (perpendicular to the plane of steering wheel rotation) cancels the current speed control event, but does not turn the system OFF or clear the currently stored set speed.
- Set / Decel - Pressing the switch stalk downward (in the same plane as steering wheel rotation) sets the current vehicle speed as the stored set speed or decelerates (coasts) the vehicle to a speed that is slower than the already attained set speed.
The PCM continually monitors all of the hard wired speed control switch circuits and will set a Diagnostic Trouble Code (DTC) for any problem it detects in the speed control switch circuits. The PCM also communicate with other electronic modules over the Controller Area Network (CAN) data bus. Therefore, any PCM DTC information can be retrieved using a diagnostic scan tool connected to the Data Link Connector (DLC).
The analog resistor multiplexed circuits of the speed control switch as well as the hard wired circuits between the switch and the PCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.
However, conventional diagnostic methods will not prove conclusive in the diagnosis of the speed control switch, the PCM or the electronic controls and communication between modules and other devices that provide some features of the speed control system. The most reliable, efficient, and accurate means to diagnose the speed control switch, the PCM or the electronic controls and communication related to speed control system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.