Normal Operation

The instrument panel dimmer switch is a rocker style switch with 2 inputs to the Body Control Module (BCM) to increase or decrease the backlighting illumination. When the instrument panel dimmer switch is pressed up or down, a ground signal is routed to the BCM.

Based on the ground signal input from the instrument panel dimmer switch, the BCM sends a message over the network to the modules with backlighting output indicating the backlighting intensity level, and provides voltage to the hard-wired dimmable illumination sources.

• DTC B134E:23 (Switch Illumination Adjustment Control: Signal Stuck low) - a continuous and on-demand DTC that sets when the BCM detects the instrument panel dimmer switch is stuck or held low for more than 2 minutes or the increase or decrease control circuits are shorted to ground. If the instrument panel dimmer switch is stuck low the BCM defaults the backlighting illumination to full backlighting intensity.

This pinpoint test is intended to diagnose the following: 

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