Brake Moment Control Circuit

NOTE: For model name/model number cross reference refer to Model Designation Table. Application and ID






The appropriate functions of the Electronic Traction Support (ETS) hydraulic unit (A7/3) are controlled by the electrical/electronic components.

On models 129 and 140 the voltage is supplied to the ETS control module (N47-2) via the base module (N16/1) and 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 ETS control module receives input signals from the following components for the ETS and Antilock Brake System (ABS) function:

^ 4 speed sensors
^ Stop lamp switch

In the ETS 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 on the Bosch version or cycling on the Teves version)
^ ETS warning lamp
^ ABS Malfunction Indicator Lamp (MIL)
^ ETS or Brake Assist System/Electronic Traction Support (BAS/ETS) malfunction indicator lamp

Based on the input signals, the ETS control module decides which of the 3 operating modes must be used:

^ Normal mode
^ ABS control mode
^ ETS control mode

Normal Mode
In this case there are no wheel speed differences (which require a control mode). All solenoid valves in the ETS hydraulic unit (A7/3) are in the initial position, i.e. switched to de-energized position. The system is ready for braking.
This operating mode is also used when ETS and ABS are switched to fault.

ABS Control Mode
From the speed signals occurring, the ETS control module (N47-2) recognizes that the criteria for ABS control exist. The appropriate solenoid valves are triggered by the ABS circuits in the ETS control module (N47-2). The left and right front axle solenoid valves in the ASR/ETS hydraulic unit (A7/3) are actuated separately (individual control). The left and right solenoid valves for the rear axle are actuated together for the ABS control process.

ETS Control Mode (Models Without AWD)
The speed signals are continuously processed in the ETS control module (N47-2).
As soon as one drive wheel tends towards spinning, the ETS control module (N47-2) actuates the self-priming high pressure/return pump (A7/3m1), the switchover solenoid valve (A7/3y5), the appropriate solenoid valves for the rear axle and, on the Bosch version, the inlet solenoid valve (A7/3y15). The left and right solenoid valves for the rear axle are triggered separately.
The ETS control mode is interrupted by operating the brake pedal.

ETS control mode (E Class Models With AWD)
The speed signals are continuously processed in the ETS control module (N47-2).
As soon as one drive wheel tends towards spinning, the ETS control module (N47-2) actuates the self-priming high pressure/ return pump (A7/3m1), the appropriate switchover solenoid valve (A713y18 or A7/3y19), the inlet solenoid valve (A73y15 or A7/3y19) of the front or rear axle circuit and the appropriate solenoid valves for the wheel brakes.
The ETS control mode is interrupted by operating the brake pedal.