General

The Lamp Module (LM) for the E38 is designed to control and monitor all the outside lights on the vehicle. Various displays and switches are also illuminated by an LM function.

The LM incorporates power transistor output stages with internal protection circuits. This eliminates the need for fuses and relays that are found on earlier lamp control systems.

The LM is located in the passenger side kick panel behind the footwell speaker. This location provides an airflow across the external heatsink to cool the LM.

The LM reduces a number of components that were used in the past. Eliminated are:
- Numerous relays
- Flasher unit
- Crash control unit (relay)
- Cold check relay
- Dimmer

- The LM transmits and receives status information concerning light operation. The LM transmits bulb status to the check control module.
- It also communicates to the IKE when turn signal, highbeam, and fog light indicators need to be activated.
- The LM is informed by ZKE when a crash has occurred or the alarm was tripped for headlight/flasher activation.
- When reverse is selected, the LM is signaled to turn on the back-up lights.

All of this communication takes place over the Bus system.







The LM monitors most of the vehicle's lighting circuits with warm and cold check functions.
- The warm check is performed by electronic diagnosis at the output stages.
- Cold checking is done by switching on the light circuits briefly. In other words, it is a very rapid warm check. This is repeated in timed cycles.

In order to simplify wiring in the E38, the LM operates the brake lights with inputs received from an electronic brake light switch.

For safety purposes, the LM is designed with emergency functions in case of failure. The failure of any one component doesn't disable the entire system.

Important vehicle-specific data is stored in the LM. Replacement of this module is covered in the IKE section of this training.

BULB MONITORING







The extent of bulb checking is governed by LM coding. Certain monitoring functions can be shut down. For instance, if Xenon low beam lights are installed, low beam cold check is turned off.

Faulty turn signal bulbs and circuits are indicted by rapid flashing of the cluster indicator.