Steering Column Module Explanation

STEERING COLUMN MODULE DESCRIPTION
This vehicle is equipped with a Steering Control Module (SCM) that is internal to the left multifunction switch housing (2). The left (lighting) multifunction switch is located on the left side of the steering column, just below the steering wheel. This switch is the primary control for the interior and exterior lighting systems. The only visible components of the switch are the control stalk (1), control knob and control sleeve that extend through the steering column shrouds on the left side of the column. The remainder of the switch including its mounting provisions and electrical connections are concealed beneath the shrouds.

The switch housing and controls are constructed of molded black plastic. A single screw (7) through a mounting tab integral to the back of the switch housing, and a slide tab integral to the bottom of the switch housing secure the switch to the mounting bracket integral to the clockspring (3). A connector receptacle containing seven terminal pins is integral to the inboard end of the switch housing and connects the SCM through a jumper wire harness (5) directly to the right (wiper) multifunction switch (6). A second connector receptacle containing four terminal pins is integral to the back of the switch housing and 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. If ineffective or damaged the entire left multifunction switch must be replaced. Refer to SWITCH, MULTIFUNCTION, LEFT, REMOVAL. The clockspring (with the multifunction switch mounting bracket), the left multifunction switch (with the SCM), the right multifunction switch and the jumper wire harness are each available for separate service replacement.

STEERING COLUMN MODULE OPERATION
The microcontroller-based Steering Control Module (SCM) utilizes integrated circuitry to monitor hard wired analog and multiplexed inputs from both the right and left multifunction switches. In response to those inputs, the internal circuitry of the SCM allow 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 the SCM inputs 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. Refer to 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 function that does not require that the ignition switch be in the ON position such as turning on the lights, 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 and 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.

STEERING COLUMN MODULE REMOVAL
WARNING: To avoid serious or fatal injury on vehicles equipped with airbags, disable the Supplemental Restraint System (SRS) before attempting any steering wheel, steering column, airbag, seat belt tensioner, impact sensor or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the SRS. Failure to take the proper precautions could result in accidental airbag deployment.

1. Disconnect and isolate the battery negative cable.
2. Remove both the upper and lower shrouds from the steering column. Refer to COLUMN, REMOVAL.
3. Disconnect the instrument panel wire harness connector from the connector receptacle on the back of the left multi-function switch.
4. Remove the screw (2) that secures the left multi-function switch (1) to the mounting bracket integral to the left side of the clockspring (3) on the steering column.
5. Slide the switch away from the clockspring far enough to disengage the slide tabs on the switch housing from the channel formations in the mounting bracket.
6. Disconnect the jumper wire harness connector from the connector receptacle on the inboard end of the left multi-function switch.
7. Remove the switch from the clockspring.

STEERING COLUMN MODULE INSTALLATION
WARNING: To avoid serious or fatal injury on vehicles equipped with airbags, disable the Supplemental Restraint System (SRS) before attempting any steering wheel, steering column, airbag, seat belt tensioner, impact sensor or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the SRS. Failure to take the proper precautions could result in accidental airbag deployment.

1. Position the left multi-function switch (1) close enough to the mounting bracket (3) integral to the left side of the clockspring to reconnect the jumper wire harness connector to the connector receptacle on the inboard side of the switch housing.
2. Align the slide tabs on the switch housing with the channel formations integral to the clockspring mounting bracket, then slide the switch into the bracket until it is firmly seated.
3. Install and tighten the screw (2) that secures the mounting tab on the front of the left multi- function switch to the mounting bracket on the clockspring. Tighten the screw to 1 N.m (10 in. lbs.).
4. Reconnect the instrument panel wire harness connector to the connector receptacle on the back of the switch housing.
5. Reinstall the upper and lower shrouds onto the steering column. Refer to COLUMN, INSTALLATION.
6. Reconnect the battery negative cable.