Parking Brake Control Module: Description and Operation

GF42.20-P-5005RD Electric Parking Brake Control Unit, Component Description
MODEL 172.4





N128 Electric parking brake control unit

A Control unit carrier

Location
The electric parking brake control unit is located at the right on the control unit carrier in the trunk.

Task
The electric parking brake control unit has the following tasks:
^ Reading in of sensors and signals
^ Evaluation of input factors
^ Actuating components

Reading in of sensors and signals
The input factors are read in via the following connections:
^ Direct line
^ Chassis CAN (CAN E)

Direct line
The signals from the following component are read in over direct lines:
- Status of electric parking brake switch (S76/15)

Chassis CAN
The following information is read in over the chassis CAN:
- Status of circuit 15R ON, from electronic ignition lock control unit (N73)
- Status of driver seat belt buckle restraint system switch (S68/3), from rear SAM control unit with fuse and relay module (N10/2)
- Status of trunk lid rotary tumbler switch (M14/7s1), from front SAM control unit with fuse and relay module (N10/1), which receives the status from the rear SAM control unit with fuse and relay module over the interior CAN (CAN B)
- Roadway inclination, from Electronic Stability Program control unit (N30/4), which receives the signal over the vehicle dynamics CAN (CAN H) from the yaw rate sensor for lateral and longitudinal acceleration (with code (233) DISTRONIC PLUS), or directly determined by the Electronic Stability Program control unit (without code (233) DISTRONIC PLUS)
- Wheel speeds and enable signal from Electronic Stability Program control unit
- Selector lever position from electronic selector lever module control unit (N15/5), status of circuit 61 ON and the accelerator pedal position, from the CDI control unit (N3/9) (with engine 651.9) or ME-SFI [ME] control unit (N3/10) (with engine 271.8 or 276.9)

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.

Component actuation
The actuation of the components takes place via the following connections:
^ Direct line
^ Chassis CAN

Direct line
The electric parking brake control unit actuates the left electric parking brake actuator motor (M76/1) and the right electric parking brake actuator motor (M76/2) via a direct line.

Chassis CAN
The following components are actuated via the chassis CAN:
- Instrument cluster (A1) (output of messages and warnings)
- Electronic Stability Program control unit (initiates emergency brake application)