Antilock Brakes / Traction Control Systems: Service and Repair
ABS/Electronic Stabilization Program (ESP) Overview, Bosch
The Bosch ESP 8.1 has the following functions:
• ABS - Antilock braking system
• ASR - Anti-slip regulation
• EBD - Electronic brake pressure distribution
• EDL - Electronic differential lock
• ESP - Electronic stabilization program
• FBS - Fading brake support
• HBA - Hydraulic brake assist
• MSR - Engine drag torque regulation
• Emergency braking signal
• Brake rotor cleaning
• Trailer stabilization
The brake system is distributed diagonally. The vacuum brake servo unit boosts the brakes pneumatically.
• ABS malfunctions do not affect the brake system and the booster. Conventional brake system stays operative even without ABS. A change in braking behavior should be checked. When the ABS warning lamp comes on the rear wheels can lock-up early when braking!
Malfunction sources are reduced by direct connection of components named. The components are replaced instead of repaired.
1 - Right Rear ABS Wheel Speed Sensor (G44)
• Removing and Installing, refer to => [ Right Rear ABS Wheel Speed Sensor (G44) and Left Rear ABS Wheel Speed Sensor (G46) ] Right Rear ABS Wheel Speed Sensor (G44) and Left Rear ABS Wheel Speed Sensor (G46)
• Can be tested in "guided fault finding" with the vehicle diagnostic tester (VAS 5051B) or (VAS 5052).
2 - Left Rear ABS Wheel Speed Sensor (G46)
3 - ESP-Sensor Unit (G419)
• Component location: under the left seat.
• Removing and Installing, refer to => [ ESP Sensor Unit (G419) ] ESP Sensor Unit (G419).
• 9 Nm
• Combined transverse acceleration sensor G200, rotation rate sensor G202 and longitudinal acceleration sensor G251.
• Can be tested in "guided fault finding" with the vehicle diagnostic tester (VAS 5051B) or (VAS 5052).
• Observe installation instructions
• Check the arrow in the direction of travel when installing
4 - Brake Lamp Sensor
• Component location: on brake pedal.
• Removing and Installing, refer to => [ Brake Lamp Sensor ] Service and Repair.
• Can be tested in "guided fault finding" with the vehicle diagnostic tester (VAS 5051B) or (VAS 5052)
Cannot be reused after removal.
5 - Brake Pedal
• With bracket for the brake lamp sensor.
• Removing and Installing, Manual Transmission, refer to => [ Brake Pedal, Manual Transmission ] Brake Pedal, Manual Transmission.
• Removing and Installing, Automatic Transmission, refer to => [ Brake Pedal, Automatic Transmission ] Brake Pedal, Automatic Transmission.
6 - Electromechanical Parking Brake Indicator Lamp
• Located in the tachometer.
• Lights up when the parking brake is engaged and the ignition is switched on.
• Lights up for 20 seconds when the parking brake is engaged and the ignition is switched off.
• Blinks after engaging the parking brake if the brake pressure is not sufficient to prevent the vehicle from rolling.
7 - Brake System Indicator Lamp (K118)
• Located in the tachometer.
• Turns on with the ABS indicator lamp when the ABS system malfunctions.
• Blinks when the brake fluid is too low.
• Blinks when there is a malfunction in the brake system.
• The malfunction is indicated more precisely when the "SET button" in the instrument cluster is pressed.
8 - ABS Indicator Lamp (K47)
• The indicator lamp monitors the ABS and the Electronic Differential Lock (EDL).
• Component location: in the tachometer.
• Lights up for several seconds when ignition is switched on and goes out after an automatic ABS system self-check if there are no malfunctions in the ABS system.
• There is an ABS malfunction if the indicator light:
• Does not light up when ignition is switched on,
• Does not go out after a few seconds,
• Lights up while driving.
• ABS malfunctions have no effect on the brake system. However, a change in braking behavior should be checked.
• The Electronic Differential Lock (EDL) and ABS work together. The ABS indicator light lights up when the EDL malfunctions.
9 - ASR/ESP Indicator Lamp (K155)
• Component location: in the tachometer.
• Blinks when driving if ESP/ASR engages regularly.
• Comes on when ignition is switched on and goes out after a short self-check.
• Comes on if there is an ESP system malfunction.
• Comes on if there is an ABS system malfunction because ESP and ABS work together.
• Comes on when the ASR is switched off.
• Comes on during sensor programming if:
• The battery was disconnected and connected.
• Vehicle was started with jump start.
• The battery is too weak.
• After the sensor programming procedure, the ESP light goes out after driving a short distance.
10 - Left Front ABS Wheel Speed Sensor (G47)
• Removing and Installing, refer to => [ Right Front ABS Wheel Speed Sensor (G45) and Left Front ABS Wheel Speed Sensor (G47) ] Right Front ABS Wheel Speed Sensor (G45) and Left Front ABS Wheel Speed Sensor (G47).
• Can be tested in "guided fault finding" with the vehicle diagnostic tester (VAS 5051B) or (VAS 5052).
11 - ABS Hydraulic Unit with ABS Control Module (J104)
• Removing and Installing, refer to => [ ABS Hydraulic Unit (N55) with ABS Control Module (J104) ] ABS Hydraulic Unit (N55) With ABS Control Module (J104).
12 - Return Ring
• Removing and Installing, refer to => [ Steering Angle Sensor (G85) ] Service and Repair.
13 - Steering Angle Sensor (G85)
• Component location: Installed in coil ring with slip ring on steering column => 69.
• Removing and Installing, refer to => [ Steering Angle Sensor (G85) ] Service and Repair.
• Perform zero adjustment.
Vehicle diagnostic tester (VAS 5051B) or (VAS 5052)
14 - Right Front ABS Wheel Speed Sensor (G45)
15 - ASR/ESP Button (E256)
• Component location: Inside center console.
• Switches the ASR off and on.
16 - Audi Hold Assist Pressure Switch
• Located in the center console.
• Function, refer to => [ Audi Hold Assist ] Audi Hold Assist.
• Removing and Installing, refer to => [ Audi Hold Assist Switch ] Service and Repair.
17 - Parking Brake Pressure Switch (F234)
• Located in the center console.
• Removing and Installing, refer to => [ Parking Brake Switch (F321) ] Parking Brake Switch (F321).
18 - Diagnostic Connection
• Component location: cover in driver footwell.
Diagnostic Connection
