Module, Steering Column Control (SCCM): Operation

The Steering Column Control Module (SCCM) includes an electronic circuit board with a microcontroller. The microcontroller is a Local Interface Network (LIN) bus master node and a gateway for the Controller Area Network (CAN) data bus. Refer to COMMUNICATION, DESCRIPTION . The SCCM microcontroller provides power and ground to the multifunction and power tilt and telescope steering column switches of the SCCM, then utilizes integrated circuitry to monitor hardwired analog and digital return inputs from each of these switches. The circuits for the horn switch, the optional heated steering wheel and the standard equipment Driver AirBag (DAB) are pass-through circuits of the SCCM. The steering wheel-mounted electronics functions monitored by the SCCM include the paddle shifter switches and the cruise switches. The output of the horn switch is hardwired to the Body Control Module (BCM) (also known as the Common Body Controller/CBC).

The switch pods in the left and right horizontal spokes of the steering wheel are each LIN bus slave nodes. The switch states of the hands-free communication switches and the Electronic Vehicle Information Center (EVIC) control switches in the left switch pod are communicated over the LIN bus directly to the LIN bus master node of the BCM. The left switch pod also controls the back lighting of both switch pods and both paddle shifter switches. The switch states of the speed control switches in the right switch pod are communicated over the LIN bus to the LIN master node of the SCCM. The internal circuitry of the SCCM gateway then relays electronic message outputs communicating those switch states as well as Steering Angle Sensor (SAS) data to other electronic modules in the vehicle over the CAN bus.

A fixed connector receptacle of the SCCM connects to the vehicle electrical system through a single take out with connector from the instrument panel wire harness. The instrument panel wire harness take out has been intentionally provided with additional length to facilitate service removal and installation of the SCCM. However, following SCCM installation, this additional length must be pulled back and secured to the instrument panel structure to prevent the potential for undesirable rattling or buzzing noises while driving.

The SCCM is connected to a fused B(+) circuit and receives a path to ground at all times. These connections allow it to remain functional regardless of the ignition switch status. Any input to the SCCM that controls a vehicle system function that does not require that the ignition switch status be ON such as pressing the horn switch, prompts the SCCM to wake up and transmit on the CAN data bus.

The service replacement SCCM is shipped with the clockspring pre-centered within the SCCM and with a plastic locking tab installed. This locking tab should not be removed until the SCCM has been properly installed on the steering column. If the locking tab is removed before the steering wheel is installed on a steering column, clockspring centering must be confirmed by viewing the inspection window on the clockspring rotor. If the black boxes of the clockspring tape are not visible in the inspection window, the entire SCCM must be replaced with a new unit. Refer to CLOCKSPRING, STANDARD PROCEDURE . Proper clockspring installation may also be confirmed by viewing the Steering Angle Sensor (SAS) data using a diagnostic scan tool.

The hardwired circuits between components related to the SCCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds. For proper wire repair, Refer to STANDARD PROCEDURE and connector repair procedures Refer to REMOVAL and Refer to INSTALLATION .

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the SCCM or the electronic controls and communication between modules and other devices that provide some features of the SCCM. The most reliable, efficient and accurate means to diagnose the SCCM or the electronic controls and communication related to SCCM operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.