The most important interfaces of the ABS/ASC control unit are those for the choke, digital engine electronics (DME) and for adaptive transmission control (AGS).
The data exchange between DDE, AGS and ABS/ASC does not take place by the usual means of a large number of individual wires, but rather via a serial bus system, the so-called CAN-bus (Controller Area Network). This bus system consists of two data links (CAN_L and CAN_H) and a shield (CAN_S) to protect from external spurious signals.
All users in this bus system have equal rights, i.e. each control unit can both transmit as well as receive. In the event of one user failing, the bus still remains available for the remaining users.
Note
All control units connected to the bus must feature the same bus index. This index is indicated in the diagnosis program on the first page of the control unit identification.
The ABS/ASC control unit reduces or increases the torque at the drive axle by closing or opening the choke accordingly. This intervention is the first but relatively slow measure in reducing the drive torque during ASC control.
The ABS/ASC control unit can implement the following engine interventions by way of the digital engine electronics:
Intervention |
Effect |
|---|---|
Ignition timing set towards "retard" |
Fast yet smooth reduction of drive torque |
Blanking out ignition/injection pulses |
Fast reduction of drive torque |
Increase in idle speed |
Reduction in engine drag torque on vehicles with manual transmission |
Vehicles equipped with an adaptive transmission control (AGS) can receive a signal from the ABS/ASC control unit during an ASC control phase, i.e. mainly on road surfaces with snow and ice, to the effect that imminent gearshifts, resulting in an increase in the torque in the drive axle are suppressed.