Rear Control Unit, Component Description - GF54.21-P-4134FH

Model 238 

Up To Model Year 2021 

Location 

The rear control unit is located on the control unit bracket at the center in luggage compartment.

Tasks 

The rear control unit actuates the following functions:

• Seat belt extender
• Rear window lifter

The tasks are subdivided as follows:

• Reading in of sensors and signals 
• Evaluation of input factors 
• Actuation of components 
• Sending signals 

Reading in of sensors and signals 

The input factors are read in over the following connections:

• Direct lines 
• Left rear-LIN (LIN B9) (With Code 872 (Seat heater in rear)) 
• Right rear-LIN (LIN B10) (With Code 872 (Seat heater in rear)) 
• Interior CAN (CAN B) 

Direct lines 

The rear control unit reads in the signals from the following components over direct lines:

• Left seat belt extender Hall sensor (A10b1)
• Right belt extender Hall sensor (A11b1)
• Hall sensor in left rear power window motor (M10/5)
• Hall sensor in right rear power window motor (M10/6)
• Left rear electric window lifting mechanism switch (S21/3)
• Right rear electric window lifting mechanism switch (S21/3)
• Trunk lid lock switching element (S49)

Left rear LIN (With Code 872 (Seat heater in rear)) 

The rear control unit reads in the signals from the left rear seat heater switch (S51/3) over the left rear LIN.

Right rear LIN (With Code 872 (Seat heater in rear)) 

The rear control unit reads in the signals from the right rear seat heater switch (S51/4) over the right rear LIN.

Interior CAN 

The rear control unit also reads in the following signals via interior CAN:

• Circuit 15 status
• Open/close rear window request
• Crash signal

Evaluation of input factors 

The input factors that have been read in are evaluated by the integrated microprocessor and the relevant components are then actuated.

Actuation of components 

The rear control unit actuates the following components over direct lines:

• Left seat belt extender electric motor (A10m1)
• Right seat belt extender electric motor (A11m1)
• Left rear power window motor
• Right rear power window motor

Sending signals 

The rear control unit also sends signals over the interior CAN:

• Seat belt extender status
• Rear electric window lifting mechanism status

Wiring diagram of rear control unit

PE54.21-P-2110-97DCA