Dimmable Backlighting

The dimmable switches and components are illuminated when the parking lamps are on. The instrument panel dimmer switch, which is integral to the headlamp switch, controls all dimmable interior illuminated components.

On vehicles equipped with autolamps, if the exterior lamps are activated during the daytime, the message center illumination remains at full intensity and does not dim from the instrument panel dimmer switch during this condition. If the vehicle travels under a bridge or through a tunnel, the low level of ambient light causes the illumination level of the message center to change to the level set by the instrument panel dimmer switch. The message center illumination changes back to full intensity when the intense ambient light is restored.

If the IPC does not receive the input signals of dimming level or ambient light level for up to 5 seconds, the last valid received state of these signals is assumed. If the IPC receives invalid or no signals for more than 5 seconds, it assumes full night illumination level.

Based on the ambient light level and illumination dimmer position messages received from the BCM, the IPC calculates the correct dimming level. The IPC then sends the illumination dimming level message to the BCM, HVAC, DDM, PDM and to the Image Processing Module - B (IPM-B) on the Medium Speed Controller Area Network (MS-CAN) and also to the APIM, FCIM and FCDIM  on the Infotaiment Controller Area Network (I-CAN).

The IPC sends the illumination dimming level message over the network. The receiving modules use the illumination dimming level message to determine the backlighting intensity of integral illumination sources. The BCM sends a pulse-width modulated voltage to hardwired dimmable components on 3 circuits based on the illumination dimming level message from the IPC. If a module does not receive the illumination dimming level message or the data received is deemed invalid, the module sets a DTC in continuous memory and defaults to full night time intensity.

Field-Effect Transistor (FET) Protection 

Field-Effect Transistor (FET) protection is used to protect the BCM output drivers from damage in the event that an excessive current draw is detected on a BCM output. Each illumination circuit connected to the BCM is separately protected. Refer to the System Diagram  to view the different groups of BCM hardwired illumination outputs. For a full description of Field-Effect Transistor (FET) protection,

Refer to: MODULE CONTROLLED FUNCTIONS - SYSTEM OPERATION AND COMPONENT DESCRIPTION .