ESP Function
ESP includes the functions of EBD, ABS, EDL and ASR. The individual components have the following functions:
EBD
The two brake circuits are split diagonally. One circuit supplies the left-front and right-rear brakes with appropriate hydraulic pressure, the other supplies the right-front and left-rear.
Matched software in the ABS control module -J104-, Electronic Brake Distribution (EBD) carries out the function of the mechanical/hydraulic brake pressure regulator.
The signal sent to the instrument cluster when the ABS fails is pulsed, if the EBD function continues in emergency mode. The instrument cluster distinguishes between no signal, a pulsed signal, and a steady signal. The ABS/EDS indicator lamp and the red symbol for "Brake system malfunction" light accordingly.
1. Terminal 15
2. Signal for controlling the ABS/EDL indicator lamp and the red brake warning symbol
3. Voltage supply for the ABS/EDL indicator lamp
4. Voltage supply for the red brake warning symbol
A. In interval "A" (with "ignition on") a self-test of the ABS/EDL indicator lamp is carried out for two seconds using signal "2" (lamp lights up). During this interval, the instrument cluster suppresses the red brake warning symbol.
B. Signal "2" is not available in interval "B." The ABS/EDL indicator lamp and the red brake warning symbol do not light.
C. In interval "C", the On Board Diagnostic recognized a DTC, which did not deactivate the EBD. Signal "2" is pulsed. Only the ABS/EDL indicator lamp comes on.
D. In interval "D", the On Board Diagnostic recognized a DTC, which did deactivate the EBD. Signal "2" is steady. The ABS/EDL indicator lamp and the red brake warning symbol light.
The red brake warning symbol indicates the EBD is deactivated. The vehicle is only allowed to be driven under restricted conditions, Test Drive.
For additional information about EBD indicator lamp control, see: "Indicator lamp functions, overview".
ABS
ABS prevents the wheel from locking up during hard braking initiated by the driver. ABS regulates the brake system pressure in the individual brake cylinders with respect to the individual wheel speed, brake deceleration and slip, to ensure optimal braking of the wheels on the road surface.
EDL
The Electronic Differential Lock (EDL) is a traction control aid for driving away from a standstill. An electronically-controlled brake application at the wheel that is spinning provides a torque reaction point for the differential. This enables the wheel with better traction to make use of the engine power. EDL is effective in both forward and reverse.
On vehicles with all-wheel-drive, EDL controls all four wheels. This makes it possible to eliminate the driver operated mechanical differential lock.
EDL as part of ESP and is effective at any speed.
ASR
The function of ASR requires an exchange of signals between the ABS control module -J104-, the Engine Control Module (ECM) and the Transmission Control Module (TCM) (only for vehicles with automatic transmission). The control modules communicate with each other.
The data is transferred via CAN-bus.
The ASR traction control system prevents the driven wheels from spinning under acceleration; the system operates by reducing engine torque and is active at all speeds. The EDL and ASR functions are combined in order to assist acceleration.
ESP
The Electronic Stabilization Program (ESP) is a driving dynamics regulation system. It stabilizes the vehicle both in understeer and oversteer situations. ESP regulation includes the functions of EBD, ABS, EDS and ASR. A special function of ESP is that it can brake individual wheels.
Examples
During over-steering, the rear of the vehicle breaks out toward the outside of the curve. The vehicle rotates more on its vertical axis than required to maneuver through the curve. Braking the outside front wheel counters the over-steering effect.
In under-steering, it is the front of the vehicle that does not follow the curve. The front of the vehicle breaks out. The vehicle rotates less on its vertical axis than is required to maneuver through the curve. Braking the inside rear wheel counters the under-steering effect.
The component locations (except for the new components) are the same as the Bosch 5.0 components.
The new components:
The hydraulic pump for traction control -Y166- and the sensor for brake pressure -G201- are located in the engine compartment on the left (in the direction of travel) underneath the ABS hydraulic unit -N65-.
The ABS hydraulic unit -N65- and ABS return flow pump -V39- are supported by the hydraulic pump for traction control -V166-. This ensures brake pressure is quickly increased in the brake cylinders at each wheel, as needed.
Do not remove any bolts from the individual components, such as the ABS hydraulic unit -N65- and the hydraulic pump for traction control -V166-. The hydraulic pump for traction control -V166- and the sensor for brake pressure -G201- comprise one unit and must always be replaced as a set.
The sensor for brake pressure -G201- measures the build up of brake fluid pressure in the brake system.
The steering angle sensor -G85- is housed together with the airbag spiral spring/return spring with slip ring -F138-.
The airbag spiral spring/return spring with slip ring -F138- is slid on to the steering column shaft and secured to the steering wheel switch.
The airbag spiral spring/return spring with slip ring -F138- may be installed with or without lines for steering wheels with additional functions. The illustration shows steering wheels with additional functions.
The removal and installation procedures for the steering angle sensor -G85- are identical to those for the airbag spiral spring/return spring with slip ring -F138-.
Refer to Restraint Systems.
CAUTION:
^ Observe all safety precautions for working on airbag system.
^ Steering wheel and spiral spring must only be removed with the steering wheel in the straight ahead position.
The steering angle sensor -G85- does not have its own DTC memory. It is monitored using the DTC memory of the ABS control -J104- via the CAN-bus.
Steering angle sensor -G85- is supplied with voltage through a line connected to terminal 30. After the ignition is switched off, the sensor still uses the voltage for an hour. During this hour, the current used is a maximum 100 mA. After this hour, current used is less than 0.5 mA; the sensor is no longer active. When the ignition is switched on, the sensor is activated via terminal 15.
The current pulled from terminal 30 after the ignition is switched off is required to be able to detect a turn of the steering wheel after the ignition is off.
If the ignition was off more for than an hour, the sensor always reports a steering angle of 0 degrees. The steering angle is correctly detected only after the steering wheel was turned more than 4.5 degrees.
Yaw sensor -G202- is installed under the driver's seat (in bottom of illustration, below -G200-)
This sensor measures the rotation of the vehicle around its vertical axis (yaw).
Bolt tightening torque: 5 Nm
Sensor for transverse acceleration -G200-
Installed under the drivers' seat (in top of illustration, above -G202-)
Be careful!
The sensor for transverse acceleration is sensitive to strong vibrations.
If the sensor drops on the Ground, full function of the sensor is no longer guaranteed. If this is the case, you cannot reuse the sensor.
Bolt tightening torque: 2 Nm
The parking brake switch
Informs the ABS control module -J104- if the parking brake is set or released. This is important as the parking brake influences ESP control.
The ABS solenoid valve relay -J106- and the ABS return flow pump relay -J105
Are no longer installed in the ABS hydraulic unit -N65- as in the Bosch 5.0 system. They are now installed in the relay carrier under the driver's side storage compartment.
The function of the ESP requires that the ABS control module -J104- (item -2-) transfer data to and from the Engine Control Module (ECU) (item -3-), the Transmission Control Module (TCM) (item -4-) and the steering angle sensor -G85- (item -1-).
The data is transferred via the CAN-bus. For information and test procedure; Refer to CAN-bus,function. The CAN-bus only contains two lines. These are called bus lines. These transfer all required data. Two bus lines are used to be able to detect malfunctions in the lines.
The CAN-bus is connected in the Engine Control Module (ECM) with a resistance of approximately 66 Ohms. All other control modules connected to the CAN system (for example the ABS control module -J104-) are connected with a high ohm resistance (2.6 k Ohms).
The ASR and ESP functions can be switched on and off using the ASR/ESP switch on the center console. If the driver steps on the brake pedal, the status of the ESP switch is ignored. When braking, ESP is always active. When the ignition is switched on, the ASR and ESP functions are activated.
You can check the function of the ASR/ESP switch by selecting the "Read Value Measuring Block" function 08, Display group 002
When switched off, the ASR/ESP indicator light is lit up in the instrument cluster. During normal operation the indicator lamp blinks three times per second.