Brake moment control circuit ASR V, function

Direct or CAN data bus

CAN data bus

ASR control module (N47-1)

AST/ETS hydraulic unit (A7/3)

High-pressure/return pump (A7/3m1)

Solenoid valves (A7/3y5 to A7/3y15)

ABS malfunction indicator lamp (A1e17)

ASR MIL or BAS/ASR malfunction indicator lamp (A1e22 or A1e48)

ASR warning lamp (A1e21)

Injection and ignition system control module (LH, HFM, ME, EVE, ERE)

EA control module (N4/1), ETC control module (N15/3) (if applicable)

Overvoltage protection relay module (K1) or base module (N16/1) or relay module (K40 or K40/4)

Left front wheel speed sensor (L6/1)

Right front wheel speed sensor (L6/2)

Left rear wheel speed sensor (L6/3)

Right rear wheel speed sensor (L6/4)

Parking brake switch (S12)

Ground terminal 31

High-pressure/return pump relay (A7/3k2, N65k4, K20/1 or K40/2k4)

Solenoid valve relay (A7/3k1, N65k3) or direct control of N47-1

Data link connector X11/4

Stop lamp switch (4-pin) (S9/1)

ASR OFF switch (S76/5)

The appropriate functions of the ABS hydraulic unit (A7/3) and the functions of the drive torque control circuit are controlled by the electrical/electronic components.

On models 129 and 140, the voltage is supplied to the ASR control module (N47/2) via the base module (N16/1), on model 202 without control module box via the overvoltage protection relay (K1), on model 202 with control module box via the front passenger/side fuse and relay module (K40/4) and on models 170 and 210 via the relay unit (K40 or K40/4).

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 and transmission control, if applicable, via CAN data line

 ASR OFF switch

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In the ASR control module, the input signals are processed into output signals for the following components:

 Solenoid valves (via relay or directly)
 Self-priming high-pressure/return pump (via relay)

 Ignition and injection system (throttle valve control valve and firing angle request or fuel cutoff for petrol engines; fuel quantity control for diesel engines) via CAN data line

 ASR warning lamp

 ABS malfunction indicator lamp
 ASR malfunction indicator lamp (controlled directly, via serial or CAN data line).

Based on the input signals, the ASR control module (N47-1) decides which 5 operating modes must be used:

 Normal mode
 ABS control mode
 ASR control mode
 MSR control mode
 ASR OFF mode.

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Normal mode

In this case there are no wheel speed differences (which requires a control mode). All solenoid valves in the ASR hydraulic unit (A7/3) are in the initial position, i.e. switched to the de-energized position. The system is ready for braking.

This operating mode is also used when ASR or ABS are switched to fault.

The drive torque control is not activated.

ABS control mode

From the speed signals occurring, the ASR control module (N47-2) recognizes that the criteria for ABS control exist.

The appropriate solenoid valves are triggered by the ABS circuits in the ASR control module (N47-2).

The left and right front axle solenoid valves in the ASR hydraulic unit (A7/3) are actuated separately.

The left and right solenoid valves for the rear axle are actuated together for the ABS control process.

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ASR control mode

The speed signals are continuously processed in the ASR micro-computers in the ASR control module (N47-1).

As soon as one drive wheel tends towards spinning, the ASR control module (N47-1) actuates the high-pressure/return pump (A7/3m1), the switchover solenoid valve (A7/3y5), the inlet solenoid valve (A7/3y15) and the solenoid valves for the rear axle.

The left and right solenoid valves for the rear axle are triggered separately.

The ASR control mode is interrupted via the stop lamp switch by operating the brake pedal.

ASR off mode (ASR OFF)

In this switch position, the brakes are applied up to speeds of 40 km/h if one drive wheel is spinning. If other criteria for ABS control exist, the brakes may be applied up to a maximum speed of 80 km/h. However, the braking torque is continuously reduced. The brakes are not applied on both sides.

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