Transfer Case Control Unit, Basic Function - GF28.19-D-9890A
Model All with transmission 725.0
as of model year 2021
with code A4M (4MATIC)
Overview
This document contains information on:
- General
- Function requirements
- Function
General
The transfer case control unit monitors and actuates the transfer case.
Function requirements
- Ignition ON
- Drive range N engaged
Function
The engine torque is distributed by the electronically regulated multiplate clutch integrated into the transfer case between the front and rear axles.
The transfer case control unit detects wheel slip and opens or closes the multiplate clutch in accordance with the driving situation.
The transfer case control unit calculates an optimum torque distribution depending on the driving situation. The multiplate clutch is actuated by the transfer case control unit via the transfer case switchover magnet and the transfer case actuator motor.
If the multiplate clutch is open during normal driving operation, only the rear axle drives the vehicle. If the clutch is closed, the front axle comes into play. This ensures high traction and smooth handling characteristics.
The status of the ESP® (Electronic Stability Program) and ASR (anti-slip control) systems is displayed via the ESP®/ASR OFF warning lamp.