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

Model 205.3 

with code U02 (Belt extender, electric) 

Model 205.4 

Illustration shows model 205.3 

Courtesy of MERCEDES-BENZ USA

Location 

The rear control unit is located behind the side panel in the trunk on the left.

Tasks 

The rear control unit actuates the following functions:

• Seat belt extender
• Soft top (model 205.4)
• Rear power window (model 205.4)

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 via the following connections:

• Direct lines 
• Interior CAN (CAN B) 

Direct lines 

The signals from the following components are read via direct lines:

• Model 205.3:
  • Left seat belt extender Hall sensor (A10b1)
  • Right belt extender Hall sensor (A11b1)
  • Trunk lid/liftgate lock (A85/5)
• Model 205.4:
  • Soft top control hydraulic unit (A7/5) (pump temperature sensor)
  • Left belt extender Hall sensor
  • Right belt extender Hall sensor
  • Trunk lid/liftgate lock
  • Left trunk partition Hall sensor (B100/2) (with code 4U9 (Semiautomatic remaining luggage compartment partition))
  • Right trunk partition Hall sensor (B100/3) (with code 4U9 (Semiautomatic remaining luggage compartment partition))
  • Trunk partition closed Hall sensor (B100/5)
  • Hall sensor in left rear power window motor (M10/5)
  • Hall sensor in right rear power window motor (M10/6)
  • Draft stop actuator motor (M96/1) (with CODE 288 (Draft stop for convertible))
  • Wind deflector actuator motor (M96/2) (with CODE 288 (Draft stop for convertible))
• Soft top control switch (S84)
  • Draft stop and wind deflector button (S84s4) (with CODE 288 (Draft stop for convertible))
  • Electric window lifting mechanism central operating switch (S84s5)
• Left soft top locked switch (S84/1)
• Right soft top locked switch (S84/2)
• Soft top open limit switch (S84/3)
• Left lower soft top bow locked limit switch (S84/6)
• Right lower soft top bow locked limit switch (S84/7)
• Top soft top bow limit switch (S84/8)
• Left soft top compartment lid open limit switch (S84/26)
• Left soft top compartment lid locked limit switch (S84/27)
• Right soft top compartment lid locked limit switch (S84/28)
• Soft top closed limit switch (S84/31)
• Soft top lock open limit switch (S84/34)
• Soft top lock locked limit switch (S84/35)
• Trunk partition switch (S138/3) (with code 4U9 (Semiautomatic remaining luggage compartment partition))

Interior CAN 

The following signals, among others, are read in via interior CAN:

• Terminal status of terminal 15
• Belt extender request
• PRE-SAFE® adjustment request (model 205.4)
• Open/close rear window request (model 205.4)

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 following components are actuated via direct lines:

• Model 205.3:
  • Left seat belt extender electric motor (A10m1)
  • Right seat belt extender electric motor (A11m1)
• Model 205.4:
  • Soft top control hydraulic unit
  • Soft top control hydraulic unit electric motor (A7/5m1)
  • Solenoid valve 1 (A7/5y1)
  • Solenoid valve 2 (A7/5y2)
• Left belt extender electric motor
• Right belt extender electric motor
• Left rear power window motor
• Right rear power window motor
• Trunk partition motor (M24/11) (with code 4U9 (Semiautomatic remaining luggage compartment partition))
• Front soft top lock motor (M47/1)
• Draft stop actuator motor (with CODE 288 (Draft stop for convertible))
• Wind deflector actuator motor (with CODE 288 (Draft stop for convertible))
• Soft top control switch (LED, circuit 58d)

Sending signals 

The following signals, among others, are sent via interior CAN:

• Seat belt extender status
• Status of rear power windows (model 205.4)
• Soft top status (model 205.4)

	Wiring diagram rear control unit	Model 205.3 up to model year 2019 with code U02 (Belt extender, electric) Model 205.4 up to model year 2019	PE54.21-P-2110-97FBA
		Model 205.3 as of model year 2019 with code U02 (Belt extender, electric) Model 205.4 as of model year 2019	PE54.21-P-2110-97FBB