ESP Brake Moment Control Circuit Function
Program Flow Chart
MODEL 163 with CODE (472a) Electronic Stability Program (ESP)
The corresponding functions of the brake moment control circuit are controlled by the electrical/electronic components, with one or several wheels braked selectively by controlling the pressure of the brake fluid in the corresponding wheel brake cylinder.
The voltage is supplied to the ESP control module (N47-5) Via the fuse and relay module (F1).
The ESP control module (N47-5) controls all the functions of the brake moment control circuit and requires the signals of the following components for this:
4 wheel speed sensors (1-6/1, 1-6/2, 1-6/3 and 1-6/4)
Steering angle sensor (N49)
Lateral acceleration sensor (1343)
ESP yaw rate sensor (1345)
ESP brake pressure sensor 1 (1334/1)
ESP brake pressure sensor 2 (1334/2)
Stop lamp switch (S9/1)
Parking brake indicator switch (S1 2)
Engine control module (ME-SFI, N3/110) via CAN data bus
ETC control module (N15/3) via CAN data bus
ESP OFF switch (S76/6)
BAS release switch (A7/7s1)
BAS diaphragm travel sensor (A7/7bl)
In the ESP control module (N47-5) the input signals are processed into output signals for the following components:
BAS solenoid valve (A7/7y1)
Solenoid valves (A7/3y6 to A7/3yI3 and A7/3y24 to A7/3y27) in the hydraulic unit (A7/3)
High pressure and return pump relay (FIIk25) to actuate the high pressure and return pump (A7/3m1)
ESP stop lamp suppression relay (F1k6)
Engine control module (ME-SFI, N3/110) via CAN data bus ETC control module (N15/3) via CAN data bus
Warning and malfunction indicator lamps in the instrument cluster (A1) via CAN data bus:
ABS MIL (A1e17)
ETS MIL (A1e35)
ESP warning lamp (A1e41)
BAS/ESP malfunction indicator lamp (A1e47)
Based on the input signals, the ESP control module (N47-5) decides which of the following 7 operating modes will be switched on:
Normal mode
ABS control mode
ETS/ASR control mode
EBR control mode (refer to drive moment control circuit)
ESP control mode
BAS mode
Electronic brake force distribution
ESP OFF mode
Normal mode
In normal mode no driving condition exists which requires a control mode. AR the solenoid valves in the traction systems hydraulic unit (A7/3) are in the initial position, i.e. switched de-energized. The system is ready for braking. Drive moment control is not activated. This operating mode exists even if there is a fault in the BAS, ABS or ESP.
ABS control mode
The ESP control module (N47-5) recognizes from the wheel speed signals that the criteria for 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 traction systems hydraulic unit (A7/3) are actuated separately (4 channel control).
ETS/ASR control mode
As soon as a drive wheel has a tendency to spin, the ESP control module (N47-5) actuates the high pressure and return pump (A7/3m1), and the corresponding solenoid valves for the traction systems hydraulic unit (A7/3). The solenoid valves for the front and rear axle in the traction systems hydraulic unit (A7/3) are actuated separately.
ESP control mode
In the ESP control module (N47-5) the wheel speeds, steering angle, turn rate and lateral acceleration of the vehicle as well as the brake pressure on the thrust rod side and float circuit side are recorded and processed by the integrated driving condition controller. Once the input signals are evaluated, the BAS solenoid valve (A7/7y1), high pressure and return pump (A7/3m1) and corresponding solenoid valves of the traction systems hydraulic unit (A7/3) are actuated to regulate the brake pressure in the individual wheel brakes.
BAS mode
The ESP control module (N47-5) recognizes that emergency braking is taking place from the rate at which the brake pedal is operated and initiates BAS mode (refer to BAS function).
Electronic brake force distribution
Using the wheel speeds, sensitive slip monitoring of the rear wheels is carried out each time the vehicle is braked. Exceeding the permissible rear axle slip values is prevented by actuating the appropriate solenoid valves in the hydraulic unit.
ESP off mode (ESP OFF)
The drive moment control and engine braking regulation(EBR) is switched off when the ESP OFF switch (S7616) is operated. In addition the ESP stability function is canceled when accelerating and freewheeling. The ESP stability function is retained when the driver applies the brakes.
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