Normal Operation

The cruise control switches, which are integral to the LH steering wheel switch, use the Steering Column Control Module (SCCM) RUN/START voltage and the SCCM ground. The cruise control functionality is controlled through the cruise control switches, which are hardwired to the SCCM through signal and return circuits.

There are 4 cruise control switches with each switch operating a specific function that uses different resistance values. The SCCM 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 SCCM of which switch is pressed. The SCCM sends a network message over the High Speed Controller Area Network (HS-CAN) to the PCM activating and controlling the cruise control system.

The stoplamp switch is a single plunger 2-stage switch with 2 inputs to the PCM. When the brake pedal is applied, the first stage, which is a normally open stoplamp switch, closes and sends a voltage signal to the PCM deactivating the cruise control, if engaged. The second stage is the normally closed cruise control deactivator switch (integral to the stoplamp switch), which opens and removes the ground signal to the PCM when the brake pedal is firmly applied. This is a redundant signal to the PCM. There is less than one millimeter in plunger travel between the first and second stage.

This pinpoint test is intended to diagnose the following: 

• PCM not configured for cruise control
• Cruise control switches (part of the LH steering wheel switch)
• Stoplamp switch
• Cruise control deactivator switch (integral to the stoplamp switch)
• Digital Transmission Range (TR) sensor
• PCM
• SCCM
• ABS fault