ESP brake moment control circuit, function

CAN data bus

ESP control module (N47-5)

ME control module (N3/10, N3/11, N3/12)

ETC control module (N15/3)

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)

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

Parking brake switch (S12)

ESP OFF switch (S76/5)

Yaw rate sensor (N64)

ESP brake pressure sensor (B34)

Lateral acceleration sensor (B24/2)

Steering angle sensor (N49)

Voltage supply, terminal 87 (N16/1, K40)

Voltage, terminal 30

ESP hydraulic unit (A7/3)

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

Solenoid valves (A7/3y5 to A7/3y19)

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

ESP charging pump (M15)

Instrument cluster (A1)

EPC MIL (A1e43)

ESP warning lamp (A1e41)

ABS MIL (A1e17)

ESP or BAS/ESP MIL (A1e42, A1e47)

Data link connector (X11/4)

The corresponding functions of the brake moment control circuit are controlled by the electrical/electronic control components.

The voltage is supplied to the ESP control module (N47/5) on models 129 and 140 via the base module (N16/1), and on model 210 via the relay unit (K40).

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

 4 wheel speed sensors

 Steering angle sensor

 Lateral acceleration sensor

 Yaw sensor

 ESP brake pressure sensor

 Stop lamp switch

 Parking brake switch

 ME control module via CAN data line

 EGS control module via CAN data line

 ESP OFF switch

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

 Charging pump

 Solenoid valves

 High-pressure pump/return pump (via relay)

 ME control module via CAN data line

 EGS control module via CAN data line

 ESP warning lamp (serial or via CAN data bus)

 ABS indicator lamp (serial or via CAN data bus)

 ESP indicator lamp (serial or via CAN data bus)

The ESP control module (N47-5) decides which of the 6 operating modes are to be switched based on the input signals

 Normal mode

 ABS control mode

 ASR control mode

 MSR control mode

 ESP control mode

 ESP off mode

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Normal mode

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

This operating mode exists even if there is a fault in the ESP or ABS. Drive moment control is not activated.

ABS control mode

From the wheel speed signals, the ESP control module (N47-5) recognizes that the criteria for an ABS control exist and the appropriate solenoid valves in the hydraulic unit are actuated.

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 drive wheel tends to spin, the ESP control module (N47-5) actuates the charging pump (M15), the high-pressure pump/return pump (A7/3m1), the rear axle switchover solenoid valve, the rear axle pressurizing solenoid valve and the solenoid valves for the rear axle. The solenoid valves for the left or right rear axle are actuated separately.

ASR control mode is interrupted via the stop lamp switch when the brake pedal is operated.

ESP control mode

The signals of wheel speeds, steering angle, yaw of the vehicle, lateral acceleration as well as the brake pressure of the front axle circuit are recorded and processed by a vehicle condition controller in the ESP control module (N47-5). After evaluating the input signals, the charging pump (M15), pressurizing solenoid valves, switchover valves, high-pressure pump/return pump (A7/3m1) as well as the required solenoid valves are actuated in order to control the brake pressure in the individual wheel brakes.

ESP off mode (ESP OFF)

When the ESP OFF switch (S76/6) is operated the ASR drive moment control is switched off and the ESP stability function is therefore cancelled. The EBR control remains active but is switched to a less sensitive mode.

In this switch position a brake intervention occurs for one spinning drive wheel via the brake moment control circuit. If engaging conditions continue to exist, brake intervention is retained up to max. 60 km/h. However the brake torque is progressively reduced.