Steering Column Control Module
Steering Column Control Module
Description
This vehicle is equipped with a Steering Control Module (SCM), which is an electronic circuit board with a microprocessor that is internal to the multi-function switch (1) housing. The SCM is a Local Interface Network (LIN) slave and communicates over a dedicated LIN bus circuit with the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN), which is the LIN master and also provides a gateway to the Controller Area Network (CAN) data bus.
The multi-function switch is located on the left side of the steering column, just below the steering wheel. The multi-function switch provides the primary controls for the front and rear wiper and washer systems, the turn signals and for headlamp beam selection. The only visible component of the switch is the control stalk, which includes a control sleeve or ring and a control knob that extend through the shrouds on the left side of the steering column. The remainder of the switch including its mounting provisions, its electrical connection and a turn signal cancel actuator are concealed beneath the shrouds.
The switch housing and controls are constructed of molded black plastic. A single integral latch feature and slide tabs on the switch housing engage channels and a striker that are integral to the left side of the mounting bracket that is integral to the clockspring (3) to secure the switch to the steering column. Each of the switches within the multi-function switch is internally connected to the SCM. A single connector receptacle integral to the back of the switch housing connects the SCM to the vehicle electrical system through a dedicated takeout and connector of the instrument panel wire harness.
The SCM cannot be adjusted or repaired, and is not flash update capable. If ineffective or damaged the entire multi-function switch must be replaced. The clockspring (with the multi-function switch mounting bracket) and the multi-function switch (with the SCM) are each available for separate service replacement.
Operation
The microprocessor-based Steering Control Module (SCM) utilizes integrated circuitry to monitor hard wired analog and multiplexed inputs from the individual switches within the multi-function switch. In response to those inputs, the internal circuitry of the SCM allows it to transmit electronic message outputs to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) over the Local Interface Network (LIN) data bus.
In response to those LIN messages the internal circuitry and programming of the EMIC, which is also the LIN master module in the vehicle, allow it to control and integrate many electronic functions and features of the vehicle through both hard wired outputs and the transmission of electronic message outputs to other electronic modules in the vehicle over the Controller Area Network (CAN) data bus.
The SCM is connected to both a fused B(+) circuit and a fused ignition switch output (run-start) circuit. It receives a path to ground at all times. These connections allow it to remain functional regardless of the ignition switch position. Any input to the SCM that controls a vehicle system function that does not require that the ignition switch be in the ON position such as flashing the high beam headlamps, prompts the SCM to wake up and transmit on the LIN data bus.
The hard wired circuits between components related to the SCM 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 SCM or the electronic controls or communication between modules and other devices that provide some features of the SCM. The most reliable, efficient, and accurate means to diagnose the SCM or the electronic controls and communication related to SCM operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.