Module, Steering Column Control (SCCM): Operation

The Steering Column Control Module (SCCM) includes an electronic circuit board with a microcontroller. The SCCM 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 . For additional information on the clockspring. Refer to CLOCKSPRING, OPERATION . For additional information on the left multifunction switch. Refer to SWITCH, MULTIFUNCTION, OPERATION . For additional information on the right multifunction switch. Refer to SWITCH, MULTIFUNCTION, RIGHT, OPERATION .

The SCCM microcontroller provides power and ground to the multifunction switches, then utilizes integrated circuitry to monitor hardwired digital return inputs from the switches. The SCCM microcontroller also provides power and ground to all of the electronics carried on the steering wheel. The integral circuitry of the right steering wheel (speed control) switch pod or the optional Adaptive Cruise Control (ACC) switch is a LIN slave node to the SCCM microcontroller, while the integral circuitry of the left steering wheel Electronic Vehicle Information Center (EVIC) switch pod and the optional hands free communication switches is a LIN slave node to the Body Control Module (BCM).

The hardwired circuits for the standard equipment Driver AirBag (DAB), the horn switch and for the optional heated steering wheel heat circuits, as well as the LIN bus circuits from the slave node integral to the left steering wheel switch pod are pass-through circuits of the clockspring.

The steering wheel-mounted electronics monitored by the SCCM microcontroller includes the speed control/ACC switches. The LIN slave node of the right switch pod monitors the changing states of both the integral and any attached switches through both hardwired analog and digital return inputs, then communicates those switch states to the LIN master node circuitry of the SCCM microcontroller. In response to those inputs, the SCCM microcontroller CAN gateway circuitry then transmits electronic message outputs communicating all of the monitored switch state changes to other electronic modules in the vehicle over the CAN data bus.

The SCCM microcontroller is connected to a fused B(+) circuit and has a path to a clean ground at all times. These connections allow it to remain functional regardless of the ignition switch status. Any input to the SCCM microcontroller that controls a vehicle system function that does not require that the ignition switch status be ON, prompts the microcontroller 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 has been compromised and the entire SCCM must be replaced with a new unit. Refer to CLOCKSPRING, STANDARD PROCEDURE .

The Body Control Module (BCM) stores and compares vehicle configuration data with the SCCM microcontroller as well as with other Electronic Control Units (ECU) in the vehicle. This process is referred to as Programming Of Configuration of Systems Integrated (PROCSI) (also known as PROXI). If a configuration mismatch is detected, the BCM sets a Diagnostic Trouble Code (DTC). A configuration mismatch DTC will require the performance of a Restore BCM PROXI Configuration routine, or a PROXI Configuration Alignment routine 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, and connector repair procedures. Refer to STANDARD PROCEDURE , refer to REMOVAL , and Refer to INSTALLATION .

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the SCCM microcontroller 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 microcontroller or the electronic controls and communication related to SCCM operation requires the use of a diagnostic scan tool.