Description And Operation
DESCRIPTION
LHD model shown in illustration. RHD model similar.
The Steering Column Control Module (SCCM) (1) is located near the top of the steering column below the steering wheel. The SCCM includes the clockspring, the left (lighting) multifunction switch, and the right (wiper) multifunction switch.
The SCCM is secured to the steering column by an integral band clamp on the left side of the instrument panel side of the SCCM. The SCCM has a centering latch located on the top right of the instrument panel side of the SCCM to be certain the SCCM is centered properly.
There are also unique lugs cast into the outer circumference of the steering wheel hub that must be engaged into slots within the inner circumference of the clockspring rotor hub to unlock and drive the clockspring. The steering wheel must be tightened to specification to ensure proper clockspring function.
The SCCM includes four integral connector receptacles that face toward the instrument panel and are connected to the vehicle electrical system through four take outs and connectors of the instrument panel wire harness. The connector receptacle near the top of the back of the unit facing toward the instrument panel contains the circuits for the multifunction switches. The connectors near the bottom of the unit contain the circuits for the clockspring and the receptacles on the steering wheel side of the clockspring.
The upper surface of the rotor hub (clockspring) has short pigtail wires with connectors. The pigtail connectors contain the circuits for the Driver AirBag (DAB). The connector receptacles on the steering wheel side of the clockspring contain the circuits for the other switches mounted on the steering wheel.
The service replacement SCCM is shipped pre-centered and has a spring actuated molded plastic automatic locking ring installed. The automatic locking ring secures the centered clockspring rotor to the SCCM case during shipment and handling, and automatically releases the rotor when the steering wheel is installed. However, it is recommended that an additional strap be installed through the two retainer loops integral to the outer circumference of the SCCM to secure the rotor to the case whenever the SCCM is removed from the steering column to prevent accidental loss of clockspring centering.
The SCCM cannot be adjusted or repaired. If ineffective or damaged or the DAB has been deployed, the entire SCCM must be replaced.
OPERATION
The SCCM in this vehicle does not have any connection to the Control Area Network (CAN) and instead has two dedicated Local Interface Network (LIN) data buses used by the steering wheel switches for transmission of resistor multiplexed momentary signals to the Body Control Module (BCM). All other circuits used by the steering wheel components are hardwired pass-through circuits. The circuits for the horn switch, the optional heated steering wheel and the standard equipment DAB are pass-through circuits of the SCCM.
The switch pods (if equipped) 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. 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 BCM. The internal circuitry of the BCM gateway then relays electronic message outputs communicating those switch states, turn signal and wiper stalk data to other electronic modules in the vehicle over the CAN - C bus.
Four fixed connector receptacles on the SCCM connect to the instrument panel wire harness via four wiring harness connectors.
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 BCM to wake up and transmit on the CAN data bus.
The service replacement SCCM is shipped with the clockspring 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 may be compromised. If the clockspring centering is compromised, the entire SCCM must be replaced with a new unit.
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 . and. Refer to REMOVAL . Refer to INSTALLATION .