4Matic Electronic Traction System, Function - GF42.35-P-1000AVN

Model 257 (except 257.361) with transmission 725.0 up to model year 2021 

Function requirements for electronic traction system 4MATIC, general 

• Drive train operational/engine running
• Electronic Stability Program (ESP®) not deactivated

Electronic traction system 4MATIC, general 

The electronic traction system is a system which operates automatically for improving the starting off and acceleration ability under different road surface conditions. It replaces the automatic locking differential. The system operates through an intervention by the Brake system at the drive wheels. The electronic traction system prevents one-sided spinning of the drive wheels when starting off and accelerating as well as the drive wheels spinning briefly on both sides when cornering within specified vehicle speed ranges.

Function sequence for electronic traction system 4MATIC 

If the Electronic Stability Program control unit (N30/4) recognizes one or several spinning wheels through the wheel speed signals, the required Brake pressure is built up automatically on the spinning wheel by the traction system hydraulic unit (A7/3) in order to Brake the spinning wheels. Simultaneously, the resulting locking differential effect transfers the drive torque to the wheels that are not spinning. To keep the vehicle in a controllable driving condition, the wheel specific interventions are accompanied by a torque reduction through the CDI control unit (N3/9) (with diesel engine) or the ME control unit (N3/10) (with gasoline engine), which receives the signal torque reduction from the Electronic Stability Program control unit over the suspension FlexRay (Flex E), drivetrain control unit (N127) and the drive train CAN (CAN C1). To prevent any downshifting, the CDI control unit or the ME-SFI [ME] control unit sends the ESP® intervention status to the control unit for the electrical controller unit fully integrated transmission control (Y3/8n4) over the drive train CAN.

The ESP® warning lamp in the instrument cluster (A1) indicates when a wheel speed no longer matches the vehicle speed. To do this, the Electronic Stability Program control unit sends the signal for actuating the warning display for the Electronic Stability Program over the suspension FlexRay, the electronic ignition lock control unit (N73) and the user interface CAN (CAN HMI) to the instrument cluster. The warning lamp ESP® warns the driver that he is approaching the physical driving limits with his vehicle.