Normal Operation

The Steering Column Control Module (SCCM) sends voltage signals to the instrument panel dimmer switch (one for dim up, one for dim down, one for courtesy lamp request). When the parking lamps are on, the dimmable backlighting intensity can be changed by pressing the instrument panel dimmer switch to the first detent up or first detent down. When the instrument panel dimmer switch is placed in the first detent up or down, the corresponding input signal is routed back to the SCCM to an internal ground indicating a request to turn the dimmable lighting up or down. The SCCM retains the last brightness setting between uses.

Based on the input received from the instrument panel dimmer switch, the SCCM sends a message over the network to the Body Control Module (BCM). The BCM sends a network message to the backlit modules indicating the backlighting intensity level and a voltage to the non-networked dimmable illumination sources.

When the instrument panel dimmer switch is pressed to the second detent, the dome lamp request input circuit is routed to ground in addition to the dimmer up or dimmer down input circuit. The SCCM needs a dimmer up/down input circuit and the dome lamp request input circuit to turn the courtesy lamps on or off from the instrument panel dimmer switch.

If the SCCM detects a concern with the dim up, dim down or the dome lamp request input circuit, the backlighting defaults to full nighttime brightness.

The instrument panel dimmer switch is a momentary contact switch.

• DTC B1124:09 (Lamp Fade Control: Component Failure) - a continuous and on-demand DTC that sets when the SCCM detects a short to ground from the dim up, dim down or dome lamp request input circuits.

This pinpoint test is intended to diagnose the following: 

• Wiring, terminals or connectors
• Instrument panel dimmer switch
• SCCM