Normal Operation

The Smart Junction Box (SJB) sends voltage signals to the instrument panel dimmer switch to monitor a request to turn up the dimmable lighting, turn down the dimmable lighting and to turn the courtesy lamps on or off. When the instrument panel dimmer switch is placed in the first detent up or down, the corresponding input signal is routed to ground indicating a request to turn the dimmable lighting up or down. 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.

When the parking lamps or headlamps are ON, the Smart Junction Box (SJB) monitors the input from the instrument panel dimmer switch to increase or decrease the dimmable lighting intensity.

If the dim up/dim down or the dome lamp request input circuit is shorted to ground for longer than 17 seconds, the SJB defaults the backlighting to full nighttime brightness.

• 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 dimmer up, dimmer down or dome lamp on/off request input circuit.

This pinpoint test is intended to diagnose the following: 

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