Normal Operation

The Smart Junction Box (SJB) sends voltage signals to the instrument panel dimmer switch (one for dim up and one for dim down). 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 switch is pressed to the first detent (either up or down), the corresponding voltage signal is routed back to the SJB to an internal ground indicating a request to increase or decrease the backlighting intensity. The SJB retains the last brightness setting between uses.

The instrument panel dimmer switch is a momentary contact switch.

• DTC B1685 (Lamp Dome Input Circuit Failure) - an on-demand DTC that sets when the SJB detects a short to ground from the dimmer up or dimmer down input circuit.
• DTC B1688 (Dome Lamp Input Circuit Short To Ground) - an on-demand DTC that sets when the SJB detects a short to ground from the dome lamp request input circuit.
• DTC B213A (Digital Dimmer Switch Input Circuit Failure) - a continuous and on-demand DTC that sets when the SJB detects multiple inputs active from the dimmer switch input circuits (dim up, dim down and/or dome lamp request).

This pinpoint test is intended to diagnose the following: 

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