ESP Brake Moment Control Circuit Functions

Terminology
- ESP Electronic Stability Program
- ETC Electronic Transmission Control
- BAS Brake Assist System
- MIL Malfunction Indicator Lamp
- ABS Anti-lock Brake System
- ASR Acceleration Slip Regulation
- MSR Engine Braking Regulation
- CAN Controller Area Network
- DTR Distronic Function
- ME-SFI Engine Control Module
- EA Electronic Accelerator
- EBR Engine Braking Regulation
- SPS Speed-sensitive Power Steering

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

The voltage supply, terminal 30 of the ESP, SPS and BAS control module (N47-5) via the left fuse and relay box (K4016); terminal 87 via the right fuse and relay box (F1/1).

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

- 4 wheel speed sensors
- Steering angle sensor via CAN data bus
- Lateral acceleration sensor
- ESP yaw rate sensor
- ESP brake pressure sensor
- Stop lamp switch
- Parking brake switch via CAN data bus
- Engine control module via CAN data bus
- ETC control module via CAN data bus
- ESP OFF switch
- BAS release switch
- BAS diaphragm travel sensor

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

- BAS solenoid valve
- Solenoid valves in the hydraulic unit
- High-pressure/return pump (via relay)
- Engine control module (ME-SFI) via CAN data bus
- ETC control module via CAN data bus
- ESP malfunction indicator lamp via CAN data bus
- ABS MIL via CAN data bus
- Malfunction display lamp via CAN data bus
- Stop lamp via rear SAM

Based on the input signals the ESP, SPS and BAS control module (N47-5) decides which of the following 8 operating modes have to be switched

- Normal mode
- ABS control mode
- ASR control mode
- MSR control mode (refer to drive moment control circuit)
- ESP control mode
- ESP off made
- BAS mode
- DTR control module,

Normal Mode
In this case no driving condition exists which requires a control mode. All solenoid valves in the ESP hydraulic unit (A7/3) are in the initial position, i.e. de-energized. The system is ready for braking.
This operating mode exists even if there is a fault in the ESP, BAS or ABS. Drive moment control is not activated.

ABS Control Mode
The ESP, SPS and BAS control module (N47-5) recognizes from the wheel speed signals that the criteria f or an ABS control exist 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 separately (4-channel control).

ASR Control Mode
As soon as a drive wheel tends to spin, the ESP, SPS and BAS control module (N47-5) actuates the high-pressure/return pump (A73m1), the rear axle switchover solenoid valve, the rear axle charging solenoid valve and the solenoid valves for the rear axle. The solenoid valves for the left or right of the rear axle are actuated separately.

ESP Control Mode
In the ESP, SPS and BAS control module (N47-5)the signals of the wheel speeds, steering angle, vehicle yaw rate, lateral acceleration and brake pressure of the front axle circuit are recorded and processed by a vehicle status controller. Once the input signals are evaluated, the BAS solenoid valve (A7/7y1), inlet solenoid valves, switchover valves, high-pressure return pump (A7/3m1) and the solenoid valves required are actuated to regulate the brake pressure in the individual wheel brakes.

ESP Off Mode (ESP OFF)
The ESP drive moment control is switched off when the ESP OFF switch (S76/6) is operated and also the ESP stability function is cancelled when accelerating and free rolling. The ESP stability function continues to be retained when braking. The EBR control is switched off.
In this switch position, a brake intervention takes place via the brake moment control circuit up to 40 km/h when one drive wheel is spinning.
If other intervention conditions exist the brake intervention is maintained up to a maximum of 60 km/h. The brake moment is continually reduced however.

BAS Mode
The ESP, SPS and BAS control module (N47-5) recognizes that emergency braking is taking place from the rate at which the brake pedal is operated and introduces BAS mode, (refer to BAS f unction).

Distronic Control Mode
The signals for an ART control are send to the ESP control module from the Distronic (DTR) control module. There the requests are prioritized and passed on to the engine control module and, if necessary, a brake intervention is carried out by actuating the BAS solenoid valve.
The transmission display and warning function of DTR is passed on directly to the appropriate recipients.