Ford Explorer: Instrument Panel and Interior Switches Illumination / Description and Operation - Instrument Panel and Interior Switches Illumination - System Operation and Component Description

System Operation

System Diagram - Networked Illumination

Network Message Chart

  Module Network Input Messages - ACM, APIM, DDM, FCIM, RHVAC, GWM, IPC and PDM.

Networked Illumination Operation

The dimmable switches and components are illuminated when the parking lamps are on. The system-wide illumination dimming level is determined by the BCM using the ambient light level input from the light sensor and the requested illumination dimming level input from the dimmer switch. The BCM sends the illumination dimming level message to the GWM on the HS-CAN1.

The GWM distributes the message to the following components:

MS-CAN

• FCIM
• RHVAC
• DDM
• PDM

HS-CAN3

• IPC
• APIM
• ACM

The receiving modules use the illumination dimming level message to determine the backlighting intensity of internal and external non-networked illumination sources. If a module does not receive the illumination dimming level message or the data received is deemed invalid, the module sets a continuous memory DTC and defaults to full nighttime intensity.

If the IPC does not receive the dimming level or ambient light level network messages from the BCM for up to 5 seconds, the IPC illumination remains at the last level based on the last message received. If the IPC receives invalid or no signals for more than 5 seconds, the IPC defaults to full nighttime illumination level.

On vehicles equipped with autolamps, if the exterior lamps are activated during the daytime, the message center illumination remains at full intensity and it cannot be dimmed using the illumination dimmer switch. 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 illumination panel dimmer switch. The message center illumination changes back to full intensity when the intense ambient light is restored.

The hazard switch is integral to the FCIM and cannot be serviced separately.

System Diagram - Non-Networked Illumination

Non-Networked Illumination Operation

The BCM provides voltage to the rear seat control switches and the liftgate release switch with the key ON. The illumination for these switches are non-dimmable.

For the rest of the non-networked illumination, the BCM uses the ambient light level input from the light sensor and the requested illumination dimming level input from the dimmer switch to calculate the correct dimming level. The BCM provides a pulse-width modulated voltage to the non-networked illumination sources.

Field-Effect Transistor (FET) Protection

Field-Effect Transistor (FET) protection is used to protect the BCM output drivers from damage in the event 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 in this section to view the different groups of BCM non-networked illumination outputs. For a full description of Field-Effect Transistor (FET) protection,
Refer to: Module Controlled Functions - System Operation and Component Description (419-10 Multifunction Electronic Modules, Description and Operation).

Component Description

Dimmer Switch

The illumination dimmer switch is a momentary contact switch that is integral to the headlamp switch. The headlamp switch communicates with the BCM over a LIN circuit. When the illumination dimmer switch is pressed up or down, the requested illumination level is sent to the BCM.