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

Model 253 with transmission 725.096 

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 bring the vehicle into a controllable driving condition, a torque reduction is introduced by the ME-SFI [ME] control unit (N3/10) at the same time as wheel-specific brake applications. For this, the ME-SFI [ME] control unit receives the request for torque reduction in a CAN message from the Electronic Stability Program control unit over the suspension FlexRay (Flex E), powertrain control unit (N127) and the drive CAN (C1). To prevent any downshifting, the ME-SFI [ME] control unit sends the ESP® intervention status to the fully integrated transmission control, control unit (Y3/8n4) via the drive train CAN.

The Electronic Stability Program warning lamp (A1e41) signals in the instrument cluster (A1) when a wheel speed no longer agrees with the vehicle speed. The signal to actuate the Electronic Stability Program warning lamp and to issue display messages, for example, for status and fault messages for the ESP®, various CAN messages are sent by the Electronic Stability Program control unit over the suspension FlexRay, electronic ignition lock control unit (N73) and the user interface CAN (CAN HMI) to the instrument cluster. The Electronic Stability Program warning lamp thus warns the driver that he/she has approached the physical driving limits with his/her vehicle.