ESP braking moment control circuit, function

SBC CAN

CAN B

CAN C

ESP, SPS [PML] and BAS control unit (N47-5)

SBC control unit (A7/3n1)

Engine control unit

ETC [EGS] control unit (N15/3/)

Parking brake switch (S12)

Datalink connector (X11/4)

Instrument cluster (A1)

ESP and ABS warning lamp (A1e41)

ABS indicator lamp (A1e17)

Multifunction displays (A1p13, A1p15)

Lower control panel control unit (N72/)

Control unit

Left SAM (N10/6)

EIS [EZS] control unit (N73)

Steering column tube module

(N80)

Steering angle sensor

(N49)

Sensor for rotational speed and lateral acceleration (B24/15)

Circuit 31, ground

Voltage at circuit 87

ESP OFF switch (N72s14)

Voltage is supplied to terminal 87 of the ESP, SPS [PML] and BAS control unit (N47-5) via the passenger-side fuse and relay module (K40/4).

The ESP, SPS [PML] and BAS control unit (N47-5) receives input signals from the following components:

 4 wheel speed sensors (via SBC control unit)

 Steering angle sensor via the CAN data line

 Lateral acceleration sensor

 Yaw rate sensor

 SBC control unit via CAN data line

 ABC control unit via CAN data line

 DTR control unit via CAN data line

 Vehicle power supply control unit via CAN data line

 Engine control unit via CAN data line

 ETC [EGS] control unit via CAN data line

 ESP Off switch via CAN data line

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The input signals are processed into output signals for the following components in the ESP, SPS [PML] and BAS control unit (N47-5):

 SBC control unit via CAN data line

 Engine control unit via CAN data line

 ETC [EGS] control unit via CAN data line

 ESP and ABS warning lamp via CAN data line

 ABS indicator lamp via CAN data line

 Multifunction display via CAN data line

Based on the input signals the ESP, SPS [PML] and BAS control unit (N47-5) decides which of the 8 operating modes

 Normal mode

 ABS control mode

 ASR control mode

 MSR-closed-loop operation (see drive torque control circuit)

 ESP control mode

 ESP OFF mode

 BAS mode

 DTR closed-loop operation

have to be engaged.

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Normal operation

No closed-loop operation is required in this case.

This operating mode exists even if a fault exists in the ESP, BAS or ABS. Drive torque control is not activated.

ABS control mode

From the wheel speed signals the ESP, SPS [PML] and BAS control unit (N47-5), detects that the criteria for an ABS control exist and the appropriate solenoid valves in the hydraulic unit are actuated via the SBC control unit.

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

ASR control mode

As soon as a drive wheel tends to spin, the ESP, SPS [PML] and BAS control unit (N47-5) actuates the appropriate rear axle solenoid valves via the SBC control unit.

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ESP control mode

In the ESP, SPS [PML] and BAS control unit (N47-5) the signals of the wheel speeds, the steering angle, the rotational speed of the vehicle, the lateral acceleration as well as the brake pressures of the individual wheels are recorded and processed by a drive status regulator. After evaluating the input signals the required solenoid valves are actuated via the SBC control unit in order to regulate the brake pressure in the individual wheel brakes.

ESP Off mode (ESP OFF)

When the ESP OFF switch is operated (N72s14) the ESP drive moment control and the ESP stability function is canceled when accelerating and in the case of rolling freely. Only the ESP stability function is retained when braking.

With the switch in this position, braking force is applied to one spinning drive wheel via the braking moment control circuit at vehicle speeds of up to 40 km/h. If cut-in conditions continue to be present, the intervention in the brake system is retained up to a maximum of 60 km/h. However the braking torque is continuously reduced.

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BAS mode

From the speed of the brake pedal the ESP, PML and BAS control unit (N47-5), detects that an emergency case braking exists and introduces the BAS mode, (see BAS function).

Distronic closed-loop operation

The signals for a DTR control are sent from the Distronic (DTR) control unit to the ESP, SPS [PML] and BAS control unit (N47-5) There the requests are prioritized and passed on to the engine control unit and an intervention in the brake system introduced if necessary.

The transmission display and warning function of the DTR is passed on directly to the corresponding receivers.