Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Light Check Module (LCM): Notes
Upon the initial introduction of the E38 in 1995, the lighting system was controlled by the Lamp Module (LM). The LM worked in conjunction with the Check Control Module (CCM) to control and monitor exterior lights.
From 9/95 production, the LM and CCM were combined to form the Light Check Module (LCM). The new LCM provides a cost savings by combining the two functions into one processor.
It is installed in the right kick panel where the LM of the 95 E38 was installed. Both versions of instrument clusters use the LCM for processing Check Control data and controlling the exterior lighting functions of the vehicle. The LCM communicates with other modules over the "I" and "K" busses.
Functions of the LCM include:
- Monitoring of all check control inputs
- Formation and output of check control messages or signals
- Control of all vehicle external lighting
- Monitoring of all external lighting for operation
- Instrument panel illumination dimming (KL 58 g) signal
- Control of instrument cluster indicator lights - for high beam, turn signal and fog light indicators.
For proper operation of the check control and lamp control functions, the LCM must be coded with the Central Coding Key (ZCS) if replacement is required.
The LM/LCM reduces a number of components that were used in the past.
The LM/LCM replaces:
- Numerous relays
- Flasher unit
- Crash control unit (relay)
- Cold check relay
- Dimmer
The LCM transmits and receives status information concerning light operation. It also communicates to the IKE when turn signal, high beam, and fog light indicators need to be activated.
The LCM is informed by ZKE when a crash has occurred or the alarm was tripped for headlight / flasher activation.
When reverse is selected, the LCM is signaled to turn on the back-up lights. All of this communication takes place over the Bus system.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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