Normal Operation

The Smart Junction Box (SJB) 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 SJB to an internal ground indicating a request to turn the dimmable lighting up or down. The SJB retains the last brightness setting between uses.

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 SJB 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 SJB 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 B213A (Digital Dimmer Switch Input Circuit Failure) - a continuous and on-demand DTC that sets when the SJB 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
• SJB