ASR V Brake Moment Control Circuit

General
The appropriate functions in the ASR/ETS hydraulic unit (A7/3) and the functions of the drive moment control circuit are controlled by the electrical /electronic components.

The voltage is supplied to the ETS/SPS control module (N47-2) on models 129 and 140 via the base module (N16/1), on model 202 without control module box via the overvoltage protection relay module (K1), on model 202 with control module box via the fuse and relay module (K40/5) and on models 170 and 210 via the relay module (K40).

The ASR control module (N47-1) receives input signals from the following components:

^ 4 speed sensors
^ Parking brake switch
^ Stop lamp switch
^ Ignition and injection system via CAN data bus
^ ASR OFF switch

The input signals are processed into output signals in the ASR control module for the following components:

^ Solenoid valves (via relay or direct)
^ Self-priming high-pressure pump/return pump (via relay)
^ Ignition and injection system (throttle valve control value and advance angle requirement or fuel shut-off on gasoline engine or fuel quantity control on diesel engine) via CAN data bus.
^ ASR warning lamp
^ ABS indicator lamp
^ ASR indicator lamp
(Actuation - direct, serial or via CAN data bus)

The ASR control module (N47-1) decides which of the 5 operating modes must be switched based on the input signals:
^ Normal mode
^ ABS control mode
^ ASR control mode
^ MSR control mode
^ ASR Off mode

Normal Mode
No speed differences exist in this case (which require a control mode). All solenoid valves in the ASR/ETS hydraulic unit (A7/3) are switched to the normal position i.e. de-energized. The system is ready for braking. This operating mode is also used If a fault exists in the ASR or ABS.

Drive moment control is not activated.

ABS Control Mode
From the speed signals, the ASR control module (N47-1) recognizes that the criteria for an ABS control exist. The appropriate solenoid valves are actuated by the ABS switching circuits in the ASR control module (N47-1).
The left or right front axle solenoid valves in the ASR/ETS hydraulic unit (A7/3) are actuated separately.
The solenoid valves for the left or right rear axle are actuated together for the ABS control process.

ASR Control Mode
The speed signals are continuously processed in the ASR micro computers in the ASR control module (N47-1). As soon as a drive wheel tends to spin, the ASR control module (N47-1) actuates the high-pressure pump/return pump (A7/3m1), the switchover solenoid valve (A7/3y5), the intake solenoid valve (A7/3y15) and the solenoid valves for the rear axle. The solenoid valves for the left or right rear axle are actuated separately. The ASR control mode is interrupted via the stop lamp switch when the brake pedal is operated.

ASR Off Mode (ASR OFF)
In this switch position a brake intervention occurs for one spinning drive wheel in the start up range up to 40 km1h. if engaging conditions continue to exist, brake intervention is retained up to max. 80 km/h. However the brake torque is progressively reduced. Brake intervention on both sides is not used.