Cluster Illumination

WARNING: This page is about a different car, the 2017 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The IC has several Light-Emitting Diode (LED) units that serve as general illumination lighting for the IC. These LED units are illuminated whenever the exterior lighting is turned ON. The illumination intensity of these LED units is adjusted when the panel dimmer thumbwheel on the dimmer module is rotated (down to dim, up to brighten) to one of six available minor detent positions.

The Body Control Module (BCM) monitors a hard wired resistor multiplexed input from the dimmer module on a dimmer input circuit. In response to that input, the BCM sends an electronic dimming level message to the IC over the CAN data bus. The electronic circuitry of the IC then converts a fused 12-volt input it receives into a 12-volt Pulse Width Modulated (PWM) output. The IC uses this PWM output to control the illumination intensity of the general illumination of the IC and provides a hard wired PWM output to other components on the instrument panel and within the vehicle interior to control and synchronize their illumination intensity.

In addition, the thumbwheel on the dimmer module has a Parade Mode position to provide a parade or funeral mode. The BCM monitors the request for this mode from the dimmer module, then transmits an electronic dimming level message to illuminate all electronic display units in the vehicle at full (daytime) intensity for easier visibility when driving in daylight with the exterior lighting turned ON.

The hard wired headlamp switch and panel lamps dimmer inputs to and outputs from the BCM may be diagnosed using conventional diagnostic methods. However, proper testing of the PWM processing of the IC and the electronic dimming level messages sent by the BCM over the CAN data bus requires the use of a diagnostic scan tool. Refer to DIAGNOSIS AND TESTING .