Principles of Operation

Instrument Cluster and Panel Illumination

Principles of Operation

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

Dimmable Backlighting

When the parking lamps are on, the SJB provides a Pulse-Width Modulation (PWM) voltage to the dimmable instrument panel switches and components. The instrument panel dimmer switch allows the brightness level of the dimmable backlights and displays to be adjusted.

The SJB communicates with the Instrument Cluster (IC) and the Audio Control Module (ACM) through the Controller Area Network (CAN). The IC and ACM then increase or decrease the intensity of the backlighting according to the instrument panel dimmer switch position.

The dimmable components consist of the:

- IC
- ACM
- Instrument panel dimmer switch
- Message center switch
- Hazard flasher switch
- HVAC module
- Transmission Range (TR) indicator
- Convertible top switch (part of the overhead console) (if equipped)
- Steering wheel switch
- Headlamp switch

Non-Dimmable Backlighting

When the key is in the ACC or RUN positions, the SJB energizes the accessory delay relay, providing switched voltage to the non-dimmable components and switches. The non-dimmable components consist of the:

- Window control switches
- Door lock control switches

Fault Management

The SJB defaults the dimmable backlighting to full intensity if the instrument panel dimmer switch or circuitry fails.

The IC and ACM default to full nighttime brightness if they receive a missing or invalid backlighting message from the SJB.