Body Control Module: Description and Operation

Body Electrical Control Module (BeCM)
The Body electrical Control Module is an advanced microprocessor that controls most of the interior and exterior electrical functions. It also links most of the major components and systems allowing them to interact with each other for maximum reliability and performance.

The BeCM allows the driver maximum vehicle control by maintaining optimum system efficiency. It always informs the driver via the "Message Center", located in the instrument cluster, of any changes, problems or malfunctions encountered. The BeCM also controls the anti-trap safety overrides of the sunroof and windows.

Service diagnostics will utilize both TestBook and the BeCM. The BeCM logs faults and fault codes that will be retrieved using TestBook.

BeCM Wiring Harness Connections:

The introduction and use of the BeCM has eliminated the need to install a considerable number of smaller control units, timers and independent relays, and provides the following significant benefits:
- Reduced wiring harness complexity.
- Reduction in the number of control units, timers and relays.
- Increase in reliability.
- Reduction in overall weight.

A further reduction in the total number of connections and the harness complexity has been achieved by the BeCM communication.

The BeCM uses a form of electronic communication, where a microprocessor control unit, in this case the BeCM, is used to control and operate a variety of components and remote control units, in this case the outstations.

The BeCM is connected to each outstation via a serial link. Each serial link includes the following:
- A Power feed - battery supply.
- A Ground - vehicle ground.
- A Clock wire - reference.
- A Signal wire - carries instruction.
- A Direction wire - identifies direction of instruction.

This communication is used on the Range Rover 4.0/4.6 to communicate between the BeCM and the following outstations:
- Center console switch pack.
- Left and right front doors.
- Left and right memory seats.

NOTE: The instrument pack and message center are not outstations but do have serial link connections.

The BeCM controls the following:
- Exterior lighting (including bulb failure).
- Interior lighting.
- Front and rear wash/wipe systems.
- Security system (including central door locking).
- Power Window lifts and sunroof (including one-touch and anti-trap).
- Memory functions for seats, mirrors and panel illumination.
- Electric mirror operation.
- Message generation to instrument pack.
- Instrument pack audible warnings.
- On-board fault logging.
- BeCM fuses for external lights (not brake lights).

The BeCM provides power to:
- Automatic transmission TCU (Ignition Switch II).
- Transfer box ECU (Ignition Switch II).
- Cruise control ECU (Ignition Switch II), Air suspension ECU (Ignition Switch II). *
- Hevac/radio (Auxiliary Position). **
- Seats (Auxiliary Position and time function).
- SRS DCU (Ignition Switch II).

* Air suspension also requires battery feed for self leveling after six (6) hours.
**Radio also receives battery feed.

The BeCM receives and redistributes the following inputs:
- Road speed (received from ABS ECU).
- Alternator charging signal (received from alternator).
- Door open (received from switches within door locks).
- Handbrake.
- Fuel level.

BeCM - Inputs/Outputs: