Steering Column Module - Operation

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, which is a Local Interface Network (LIN) slave node, allows it to transmit electronic message outputs to the Steering Angle Sensor (SAS), which is a LIN master node as well as a gateway to the Controller Area Network (CAN) data bus, over the LIN data bus.

In response to those LIN messages as well as those from the LIN slave node within the speed control switch, the internal circuitry and programming of the SAS allow it to relay the LIN messages to other electronic modules in the vehicle. This transmission of the SCM and cruise control switch LIN message outputs over the CAN data bus helps to control and integrate many electronic functions and features of the vehicle. Communication - Description.

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 or 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.