ESP braking moment control circuit, function

CAN data bus

ESP control module
(N47-5)

ME-SFI or IFI control module (N3/10, N3/7)

ETC [EGS] control module (N15/3)

Left front rpm sensor (L6/1)

Right front rpm sensor (L6/2)

Left rear rpm sensor (L6/3)

Right rear rpm sensor (L6/4)

Stop lamp switch (S9/1)

Parking brake indicator switch (S12)

ESP OFF switch (S76/5)

Lateral acceleration sensor (B24/2)

Rotational speed sensor (N64) or combined

Yaw rate and lateral acceleration sensor (B24/15)

ESP brake pressure sensor (B34)

Steering angle sensor (N49)

Voltage supply of circuit 30, 31, 87

Stop lamp suppression relay (K55)

ESP hydraulic unit
(A7/3)

High pressure and return pump (A7/3m1)

Solenoid valves

(A7/3y6 to A7/3y23)

High pressure/
return flow pump relay (K20/1)

Instrument cluster (A1)

ESP warning lamp (A1e41)

ABS malfunction indicator lamp (A1e17)

BAS/ESP malfunction indicator lamp (A1e47)

Diagnostic data link connector X11/4

BAS brake booster
(A7/7)

BAS solenoid valve (A7/7y1)

BAS release switch (A7/7s1)

BAS diaphragm travel sensor (A7/7b1)

The functions of the braking moment control circuit are controlled using the components of the electric/electronic system.

The voltage for the ESP control module (N47-5) is supplied by the fuse and relay module (K40/2).

The ESP control module (N47-5) receives input signals from the following components:

 4 wheel speed sensors

 Steering angle sensor

 Lateral acceleration sensor

 Yaw rate sensor

 ESP brake pressure sensor

 Stop lamp switch

 Parking brake switch

 ME-SFI control module over CAN data line

 ETC control module over CAN data line

 ESP OFF switch

 BAS release switch

 BAS diaphragm travel sensor

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The input signals are processed in the ESP control module to form output signals for the following components:

 BAS solenoid valve

 Solenoid valves in the hydraulic unit

 High-pressure/return pump (via relays)

 Stop lamp suppression relay

 ME [SFI] or IFI control module via CAN data line

 ETC control module over CAN data line

 ESP warning lamp over CAN data line

 ABS indicator lamp over CAN data line

 BAS/ESP indicator lamp over CAN data line

The ESP control module (N47-5) uses the input signals to decide which of the 7 modes

 Normal mode

 ABS control mode

 ASR control mode

 EBR control mode

 ESP control mode

 ESP OFF mode

 BAS mode

must be activated.

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Normal mode

This is the case when the driving state requires no control mode. All solenoid valves in the ESP hydraulic unit (A7/3) are in the basic position, i.e. switched to the de-energized position. The system is ready for braking.

This mode also exists when there is a malfunction in the ESP, BAS or ABS system. Drive torque control is not activated.

ABS control mode

The ESP control module (N47-5) uses the wheel speed signals to detect that ABS control is required and the appropriate solenoid valves are actuated in the hydraulic unit.

The solenoid valves for the front and rear axle in the ESP hydraulic unit (A7/3) are actuated individually (4-channel control).

ASR control mode

As soon as a wheel begins to spin, the ESP control module (N47-5) actuates the high pressure and return pump (A7/3m1), the rear axle switchover solenoid valve, the rear axle charging solenoid valve and the solenoid valves for the rear axle. The solenoids for the left and right-hand side of the rear axle are actuated separately.

ESP control mode

A status controller in the ESP control module (N47-5) receives and processes the signals for the wheel speeds, the steer angle, the yaw rate of the vehicle, the lateral acceleration and the brake pressure in the front axle circuit. After evaluating the input signals, the BAS solenoid valve (A7/7y1), inlet solenoid valves, switchover valves, high pressure and return pump (A7/3m1), and the appropriate solenoid valves are actuated in order to regulate the brake pressure in the individual wheel brakes.

ESP OFF mode

If the driver presses the ESP OFF switch (S76/6) the ASR acceleration slip regulation is deactivated and the ESP stability function is also switched off when the vehicle accelerates and when rolling. The ESP stability function remains operational during braking. EBR control is deactivated.

In this switch position one brake is applied via the braking moment control circuit up to a speed of 40 km/h if one wheel spins. If activation conditions continue to exist, brake intervention continues up to max. 60 km/h. The braking torque is, however, reduced continuously.

BAS mode

The ESP control module (N47-5) uses the speed at which the driver presses the brake pedal to detect that emergency braking is required and initiates the BAS mode (refer to BAS Function).