Switch, Speed Control: Operation

WARNING: This page is about a different car, the 2017 RAM ProMaster 3500, 2017 RAM ProMaster 2500, and 2017 RAM ProMaster 1500. However, it is still accessible from the selected car via links, so may be relevant.

The speed control switch pod is a resistor multiplexed unit that provides hard wired inputs to the Body Control Module (BCM) microcontroller. The BCM relays the speed control switch inputs to the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus.

The speed control switch pod for vehicles equipped with the electronic speed control system contains four switch push buttons whose functions are:

On/Off - This switch button enables or disables the speed control system and clears any previous speed control set speed from system memory.
Resume / + - This switch button restores the vehicle to a previously stored set speed or accelerates the vehicle from an already attained set speed.
Cancel - This switch button cancels the current speed control event, but does not turn the system OFF or clear the currently stored set speed.
Set / - - This switch button 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 BCM 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. Any BCM or 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 stalk as well as the hard wired circuits between the switch stalk and the BCM 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 BCM, 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 pod, the BCM, 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.