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Body Control Module (BCM)

BCM or BCMii - “Body Control Module”

Differences between versions for FL and pre-FL can be appreciated even externally. FL version have electrical connection on the top, while pre-FL version have the connector at the side.

Pre-FL BCM FL Mondeo BCM

The BCM can be seen as the central brain of the vehicle. Virtually, there is no single module in the vehicle that operates without the BCM or that is not controlled by it. For example: vehicle lighting, central locking, alarm system, tire pressure monitoring, power supply for other modules, and many more.

The BCM contains a copy of the Central-Car-Configuration, abbreviated as “CCC”. Depending on the trim level and/or installed options, the BCM has different internal connections, which makes retrofitting of certain features impossible, or at least much more complicated. A good example of this is the missing connectors for the installation of the TPMS antennas that determine the position of the sensors.

The BCM also serves as the gateway where different interfaces connect, like OBD, HS- and MS-CAN.

The BCM module is located below the glovebox:

Folded FL BCM Folded pre-FL BCM in a RHD vehicle
Current consumption Operating mode
0.006 A Deep sleep mode, triggered by BCM
0.240 A Normal operating mode in idle, with the ignition on

There is no communication whatsoever over the CAN- or LIN- buses while in deep sleep mode. As soon as a message is detected on the CAN bus (whether HS-CAN or MS-CAN), the BCM will wake up automatically.

Follows a list of sensors, actuators and modules directly connected to, and controlled by, the BCM:

  1. Inner cabin lighting
  2. Fuel tank flap lock
  3. Tailgate lock
  4. LED daylight running lights (FL)
  5. Turn signals (front, rear, right, left)
  6. Reverse gear switch
  7. Door ajar switch, that detects whether a vehicle's door is open or closed

First, the two plastic sockets holding the lower trim must be removed, allowing the removal of the trim piece. Then, turn the yellow lock 180 degrees counterclockwise and fold the module downwards to open.

The module itself is mounted on a hinge system at its rear side. It allows itself to be open to the point to which the relays and fuses become accessible.

The BCM can be tested without the need to be connected to the vehicle. For this, it is necessary to provide a power supply as follows:

  • +12V to connector C5, pin 1 and connector C5, pin 2 (main power supply), as well as to connector C1, pin 63.
  • GND to connector C1 , pin 54 and connector C2, pin 65.

As soon as power is applied, a “click” from the battey saver relay will be audible. This relay is in charge of providing power to the inner cabin electronics. At the same time, the BCM will start sending messages over the CAN bus. Access to these buses is possible using the following pins:

  • FL:
    • HS-CAN: CAN_HIGH line accessible at connector C3, pin 6, CAN_LOW line at connector C3, pin 7.
    • MS-CAN: CAN_HIGH line accessible at connector C1 pin 30, CAN_LOW line at connector C1, pin 31.
  • pre-FL:
    • HS-CAN:
    • MS-CAN:

With the help of a CAN bus adapter (e.g. a Varianten) a connection with the CAN bus can be established and the transmitted messages can be read.

For example, the reverse gear switch signal can be emulated very nicely. In order to do this, look for the fourth byte (D3) of the message with ID 433 in a CAN bus analyzer (e.g. CANHacker). The second bit in this byte (bitmask 0b00000010) corresponds to the R signal. When not active (input to the BCM not connected and thus driven high (+12V) by the internal pull-up) the bit will have value of 0 (the decimal value of the complete byte will be 0). If the pin 29 of connector C1 (FL) is connected to ground, the bit will take a value of 1 (the decimal value of the complete byte will them be 2). At the same time, a voltage of 12V can be measured at pins 73 and 74 of connector C2. These are the outputs that control the backup lights.

  • en/artikel/bcm/start.txt
  • Last modified: Fri. 01.02.2019 16:37
  • by jphid