Principles of Operation

Instrument Cluster and Panel Illumination

Principles of Operation

Dimmable Backlighting

When the parking lamps are on, the Body Control Module (BCM) monitors the input from the instrument panel dimmer switch. The BCM sends voltage to the dimmable components based on input received from the instrument panel dimmer switch.

If a fault is detected by the BCM on the dimmable illumination output circuit, the BCM sets a DTC and disables the circuit function until the fault is cleared and an ignition cycle takes place.

The BCM also sends a message over the network to the Front Control/Display Interface Module (FCDIM) and the Instrument Panel Cluster (IPC) to control the backlighting intensity level.

If the receiving module does not receive the backlighting status message from the BCM, or if the data received is deemed invalid for more than 5 seconds, the receiving module sets a missing message related DTC in continuous memory and defaults the backlighting to full nighttime intensity.

Non-Dimmable Backlighting

When the ignition relay (located in the Central Junction Box (CJB)) is energized, switched voltage is supplied to the window control switches.

Field-Effect Transistor (FET) Protection

Field-Effect Transistor (FET) is a type of transistor that when used with module software, monitors and controls current flow on module outputs. The FET protection strategy prevents module damage in the event of excessive current flow.

The BCM utilizes an FET protective circuit strategy for many of its outputs, for example a backlighting illumination output circuit. Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down when a fault event is detected. A short circuit DTC sets when the fault occurs.

The FET protection continues to shut off the circuit so long as the fault exists. When the fault is corrected and the ignition state is cycled off and then back on, the module resets the FET protection and allows the circuit to function.

The FET protected circuit for the dimmable backlighting system is the dimmable backlighting illumination circuit.