Brake System - ABS Audi A6 C5

General information on the anti-lock brake system

ABS system, general information

The new Audi A6 is equipped with the Bosch 5.3 ABS/EDL system as standard equipment.

A traction control system (ASR) may also be installed as optional equipment on vehicles with front wheel drive.

The ABS hydraulic system is divided diagonally (two circuits). The vacuum brake servo unit boosts the brakes pneumatically.

Hydraulic unit -a- and control module - b- are combined as a single unit. This is referred to as the hydraulic control unit.

The direct connection between these components reduces possible sources of malfunctions. The hydraulic control unit is not serviceable and must be replaced if malfunctioning.

Do not remove bolts connecting individual components of the hydraulic control unit.

Scheme 431

Notes for repair work on the ABS

Note. Before carrying out repairs to the ABS, determine the cause of the malfunction using On Board Diagnostic (OBD). Always check control module coding when installing a new hydraulic control unit. See ON BOARD DIAGNOSTIC (OBD) . Always switch ignition off before carrying out installation or repair work. If the vehicle is equipped with a coded radio, obtain the security code before disconnecting the ground strap from the battery. See BATTERY DISCONNECT PRECAUTIONS . When working with brake fluid, observe relevant safety precautions and notes. After finishing any work that requires opening the brake hydraulic system, bleed the brake system (for example, using VAS 5234). During final road test, at least one ABS-controlled braking operation must be performed (appropriate pulsations must be felt at brake pedal). Absolute cleanliness is required when working on the antilock brake system. Do not use any products which contain mineral oil, such as oils, greases etc. Thoroughly clean all unions and the adjacent areas before loosening. Do not use aggressive cleaning agents such as brake cleaner, fuel, thinners or similar chemicals. Place parts that have been removed on a clean surface and cover. Carefully cover over opened components or seals, if repairs are not carried out immediately (use sealing plugs from repair kit 1 H0 698 311 A). Use lint-free cloths only! Only unpack replacement parts immediately prior to installation. Only use parts in their original packaging. Do not work with compressed air and do not move vehicle while the system is open. Make sure that brake fluid does not enter harness connectors. When painting vehicle, electronic control unit can be exposed to a maximum temperature of 95°C (203°F) only briefly, and to a maximum of 85°C (185°F) for longer periods (approx. 2 hours). Before carrying out welding work with an electric welder observe all relevant notes and safety precautions

Before beginning

Check brake system (master cylinder, brake hoses, brake lines and brake calipers) for function and proper sealing (must be free of leaks).

Scheme 432

1. Remove bleeder screw at one front brake caliper. Connect VAG1310 or VAG1310a brake pressure gauge and bleed.
2. Insert brake pedal depressor between brake pedal and driver's seat. Apply pressure to brake pedal until gauge indicates positive pressure of 50 bar (725 psi). Pressure must not drop by more than 4 bar (58 psi) during test period of 45 seconds. If drop in pressure exceeds specification: replace hydraulic control unit.

Low-pressure test

1. Move brake pedal depressor back until pressure gauge indicates pressure of 6 bar (87 ft lb). Pressure must not drop by more than 1 bar (14.5 psi) during test period of 3 minutes.

If drop in pressure exceeds specification: replace hydraulic control unit.

ABS/ESP Bosch 5.3 assembly overview

Note. The following list refers to items in (Scheme 433).

1. Electronic stabilization program hydraulic pump for traction control -V156- only with ESP Removing and installing, see «HYDRAULIC PUMP FOR ELECTRONIC STABILIZATION PROGRAM (ESP), REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
2. Sender 1 for brake booster -G201- in ESP pump (only with ESP)
3. ABS return flow pump relay -J105- for Bosch 5.3
4. ABS solenoid valve relay -J106- for Bosch 5.3
5. ABS hydraulic unit -N55- with ABS control module (w/EDL) -J104- The ABS hydraulic pump -V64-, the ABS hydraulic unit -N55- and the ABS Control Module (w/EDL) -J104- (for Bosch 5.3 only) form the hydraulic control unit.
6. Brake fluid level warning switch -F34
7. Rotor for right front speed sensor Checking, see «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__rotor-checking)
8. Right front ABS wheel speed sensor -G45- Removing and installing, see «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
9. ABS control module (w/EDL) -J104- (with ESP) Installation location: passenger footwell
10. Anti-Slip control switch - E132- Installation location: on the center console
11. Steering angle sensor - G85- (for vehicles with) ESP Installation location: Installed on the steering column Removing and installing, see «STEERING ANGLE SENSOR -G85-, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
12. Parking brake warning light switch -F9- Installation location: on the parking brake lever assembly
13. Rotor for right rear speed sensor Checking: See «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD), or «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD).
14. Right rear ABS wheel speed sensor -G44- Removing and installing: See «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD), or «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD).
15. Left rear ABS wheel speed sensor -G46- Removing and installing: See «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD), or «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD).
16. Rotor for left-rear speed sensor Checking: See «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD), or «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD).
17. Sensor for transverse acceleration -G200- New design in a housing together with -G202- 2.1 ltr quattro vehicles, MY 98 removing and installing, see «SENSOR FOR TRANSVERSE ACCELERATION -G200- AND SENDER FOR ROTATION RATE -G202- FOR BOSCH 5.3 SYSTEM IN 2.1 LTR. QUATTRO, MY 98, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) Removing and installing, see «SENSOR FOR TRANSVERSE ACCELERATION -G200- AND SENDER FOR ROTATION RATE -G202- FOR BOSCH 5.3, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__sensor-for-transverse-acceleration-g200-and)
18. Sender for rotation rate - G202- 2.1 ltr quattro vehicles, MY 98 removing and installing, see «SENSOR FOR TRANSVERSE ACCELERATION -G200- AND SENDER FOR ROTATION RATE -G202- FOR BOSCH 5.3 SYSTEM IN 2.1 LTR. QUATTRO, MY 98, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) Removing and installing, see «SENSOR FOR TRANSVERSE ACCELERATION -G200- AND SENDER FOR ROTATION RATE -G202- FOR BOSCH 5.3, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__sensor-for-transverse-acceleration-g200-and)
19. ABS return flow pump relay -J105- for Bosch 5.3 only Installation location: on fuse box
20. ABS solenoid valve relay -J106- for Bosch 5.3
21. Warning light for brake system -K118- Installation location: in the instrument cluster in the driver information system
22. ABS warning light -K47- Installation location: in instrument cluster
23. Parking brake indicator light -K14- Installation location: in instrument cluster
24. Traction control indicator light -K86- Installation location: in instrument cluster
25. Brake light switch -F- Removing and installing the brake light switch: See «ABS/ESP SYSTEM COMPONENTS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) .
26. Rotor for left front speed sensor Checking, see «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__rotor-checking) .
27. Left front ABS wheel speed sensor -G47- Removing and installing, see «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)

Scheme 433

New components

The electronic stabilization program hydraulic pump for traction control -V156- and the sender 1 for brake booster -G201- are on the left side of the engine compartment beneath the ABS hydraulic unit -N55-.

The ABS hydraulic unit -N55- with ABS return flow pump -V39- are assisted by the Hydraulic pump for traction control -V156-. This enables the system to rapidly build up the required brake fluid pressure in the wheel brake cylinders.

Scheme 434

Do not loosen the bolts securing the individual components of the ABS hydraulic unit -N55- and the Hydraulic pump for traction control -V156-. The Hydraulic pump for traction control -V156- and the Sender 1 for brake booster -G201- form a single unit and must always be replaced together if necessary.

The Sender 1 for brake booster -G201- measures the fluid pressure generated in the brake system.

ABS hydraulic control unit, assembly overview

Tightening torque for all brake lines on the Audi A6 is 15 Nm.

Note. The following list refers to items in (Scheme 435).

1. Brake master cylinder and brake servo
2. Brake line Brake master cylinder/primary piston circuit to hydraulic unit
3. Brake line Brake master cylinder/secondary piston circuit to hydraulic unit
4. Brake line Hydraulic unit to left-front brake caliper
5. Brake line Hydraulic unit to right-front brake caliper
6. Suction dampers Design to improve pressure build-up during operation of EDL To be discontinued gradually (will be incorporated in the hydraulic control unit)
7. Brake line Hydraulic control unit to left-rear brake caliper
8. Brake line Hydraulic control unit to right-rear brake caliper
9. Hex nut, 10 Nm
10. Hex bolt, 10 Nm
11. Bracket

Scheme 435

Special tools and equipment

1. VAG 1331 Torque wrench
2. VAG 1410 Torque wrench
3. VAG 1869/2 Brake pedal depressor
4. VAG 1551 Scan Tool (ST)

Scheme 436

Sealing plugs, repair kit Part No. 1H0 698 311A

Installation location

The hydraulic control unit is installed on the left side of the engine compartment.

Scheme 437

Removing

Scheme 438

1. For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary. See Caution under «GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__general-information-on-the-anti-lock-brake) before beginning repairs on the electrical system.
2. Disconnect battery.
3. Disengage connector from control module (arrow -1-) and disconnect (arrow -2-).
4. Connect bleeder bottle to bleeder screw on left-front brake caliper and open the bleeder screw.
5. Insert brake pedal depressor between brake pedal and driver's seat. Depress the brake pedal by at least 60 mm. NOTE: Do not remove brake pedal depressor until all brake lines have been reconnected to the hydraulic control unit.
6. Close left-front bleeder screw. NOTE: Cover engine compartment to make sure that brake fluid does not flow into it.
7. Disconnect brake line connections at hydraulic control unit.
8. Seal brake lines and threaded holes with plugs from repair kit Part No. 1H0 698 311 A.
9. Remove hex nuts on hydraulic control unit bracket.
10. Remove hydraulic control unit.

When installing pay particular attention to the following on points

Note. Only remove sealing plugs on new hydraulic control unit when the corresponding brake line is about to be installed. If the sealing plugs are removed too early, brake fluid can escape. If this occurs, the unit may not be sufficiently filled or adequately bled.

1. Bleeding brake system: See «BLEEDING BRAKE SYSTEM»(/audi/a6/c5-1997-2001/remont/mechanical-hydraulic/#brake-system) .
2. Enter radio code. See Caution under «GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__general-information-on-the-anti-lock-brake) for connecting Telematics battery.

Anti-lock Brake System (ABS) Bosch 5.3 with Electronic Stabilization Program (ESP)

Bleeding brake system for vehicles with ESP: See BLEEDING BRAKE SYSTEM .

Electronic stabilzation program (ESP) hydraulic unit, servicing

Tightening torque for all brake lines on the Audi A6 is 15 Nm.

Note. The following list refers to items in (Scheme 439).

1. Electronic stabilzation program (ESP), hydraulic unit If necessary, replace hydraulic unit as a unit Brake line connections, see «BRAKE LINE CONNECTIONS: HYDRAULIC CONTROL UNIT WITH ESP HYDRAULIC PUMP»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__brake-line-connections-hydraulic-control-unit)
2. Hex nut, 12 Nm
3. Bolt and washer assembly, 9 Nm (3x)
4. Spacer (2x)
5. Hydraulic pump for traction control -V156- With brake pressure switch
6. Buffer Space at hydraulic pump, 2 Nm
7. Chassis
8. Hex nut, 9 Nm
9. Bracket

Brake line connections: Hydraulic control unit with ESP hydraulic pump

Note. The following list refers to items in (Scheme 440).

1. Brake line, left-front
2. Brake line, right-front
3. Brake line to charging pump of brake master cylinder/primary piston circuit
4. Bracket
5. Line union, 30 Nm
6. Hose clamp
7. Hose
8. Hose clamp
9. Suction line
10. Brake line to charging pump
11. Brake line to brake master cylinder/secondary piston circuit
12. Protective sheathing
13. Ring connection Only in vehicles with the new version

Scheme 439

Note. Different versions of hydraulic pumps for Hydraulic pump for traction control -V156- are possible. Lines no.3 and no.10 are connected to one another via a T - piece.

Scheme 440

1. VAG 1331 Torque wrench
2. VAG 1410 Torque wrench
3. VAG 1869/2 Brake pedal depressor
4. VAG 1551 or VAG 1552

Sealing plugs, repair kit, Part No. 1H0 698 311A

Installation location

The hydraulic pump for ESP is located at left in engine compartment below hydraulic control unit.

Scheme 441

See Caution under GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM before beginning repairs on the electrical system.

Scheme 442

Scheme 443

Scheme 444

Scheme 445

1. For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary.
2. Switch off ignition and disconnect battery.
3. Raise vehicle.
4. Remove left-front wheel.
5. Remove left-front wheel housing liner.
6. Detach connectors (see arrows).
7. Remove cover for hydraulic fluid reservoir.
8. Unclip attachment strip for cable at bracket.
9. Remove mounting bolts -arrows- and swing coolant expansion reservoir to side. Tightening torque 6 Nm
10. Release bolts -1- for hydraulic fluid reservoir and swing to side. Tightening torque 10 Nm Use rubber grommet to align properly when installing.

Note. Cover engine compartment to make sure that brake fluid does not flow into it.

1. Disengage intake hose -1- from hose clamp and remove. (Scheme 447)
2. Remove brake lines -3- and -4-. (Scheme 447)
3. Seal brake lines and threaded holes using plugs from repair kit Part No. 1H0 698 311 A.
4. Unclip brake lines from holder.
5. Remove hex nut -2-. (Scheme 447)
6. Remove hex bolt from securing bracket. See «ELECTRONIC STABILZATION PROGRAM (ESP) HYDRAULIC UNIT, SERVICING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__electronic-stabilzation-program-esp-hydraulic-unit), item -3-.
7. Working from the engine compartment, lift the holder with the hydraulic unit and the hydraulic pump about 30 mm and take them out.

Scheme 446

Installing

Pay special attention to the following on installation

1. Only remove sealing plugs on new hydraulic control unit when the corresponding brake line is about to be installed. Otherwise, brake fluid will escape observe paint and corrosion protection measures.
2. Bleeding brake system on vehicles with ESP, see «BLEEDING BRAKE SYSTEM»(/audi/a6/c5-1997-2001/remont/mechanical-hydraulic/#brake-system)

See Caution under GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM before beginning repairs on the electrical system.

Brake light switch (rectangular housing), removing and installing

Brake light switch with spring clip mount.

1. Brake pedal impact surface
2. Spring clip
3. Pedal bracket
4. Brake light switch -F

Scheme 447

1. Dimension: max. 1.2 mm to min. 0.5 mm

Note. To ensure a secure fit, the switch may only be installed once.

1. Press spring clip -2- into pedal bracket opposite direction of travel. (Scheme 448)
2. Guide switch -4- into installed spring clip -2- and press/thread it in until stop.

Note. Do not pre-tension brake pedal!

1. Check dimension -a- using feeler gauge and twist brake light switch to dimension -a- if necessary. (Scheme 448)

Brake light switch (round housing), removing and installing

Note. To ensure a secure fit, the switch may only be installed once.

1. Remove driver's storage compartment. See «DRIVER'S STORAGE COMPARTMENT, REMOVING»(/audi/a6/c5-1997-2001/remont/mirrors/#interior-equipment__drivers-storage-compartment-removing) .
2. Unplug electrical connector.
3. Turn brake light switch 45° counter-clockwise to remove.

Scheme 448

Installation is carried out in the reverse sequence; note the following points

1. Pull out plunger of brake light switch as far as it will go -arrow-. (Scheme 449)
2. Insert switch into its mounting so that retaining tabs -1- and -2- engage in corresponding slots and secure by turning 45° clockwise. (Scheme 449)

Note. Do not press brake pedal while installing switch. The plunger in the switch is adjusted automatically when switch is inserted.

1. Check function of brake lights with brake pedal pressed and with pedal released.

Scheme 449

Scheme 450

Scheme 451

Scheme 452

Scheme 453

Scheme 454

1. Remove the driver's side airbag unit. See appropriate Air Bag article in RESTRAINTS.
2. Remove airbag unit and steering wheel. See appropriate Air Bag article in RESTRAINTS.
3. Wheels set to straight-ahead position. Driver airbag unit and steering wheel removed.
4. Pull steering column out and tilt downward as far as it will go.
5. Remove bolt -1- (2x), tightening torque 2.8 Nm.
6. Remove grip -2-.
7. Remove two Phillips-head screws -arrows-. (Scheme 451)
8. Tightening torque 0.6 Nm.
9. Remove upper trim panel from steering column switch -1-. When installing, insert upper shell into hooks of lower shell, swivel downward and screw in place.
10. Remove screws -2- (2x). Tightening torque 0.6 Nm
11. Remove hex socket head bolt -1-.
12. Tightening torque 0.6 Nm.
13. Remove lower trim from steering column switch -3-. The steering angle sensor -G85- is installed in housing -1- together with coil spring.
14. Remove connectors -1- and -2-.
15. Carefully lift hooks -arrows- and disconnect steering angle sensor.

Scheme 455

1. Mount steering angle sensor until tabs engage.
2. Remove transport protection.
3. A yellow dot must be visible in hole -arrow 1-.
4. The markings -arrows- must align. Make sure that center position is adhered to. The remaining installation steps are carried out in the reverse sequence
5. Install airbag unit and steering wheel See appropriate Air Bag article in RESTRAINTS.
6. Carry out basic setting of steering angle sensor -G85-. See «BASIC SETTING (SCAN TOOL FUNCTION 04)»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-on-board-diagnostic-obd-abs-esp__basic-setting-scan-tool-function-04) .

ABS control module (w/EDL) -J104- (with ESP), removing and installing

1. For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary. See Caution under «GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__general-information-on-the-anti-lock-brake) before beginning repairs on the electrical system.
2. Disconnect battery. See «BATTERY DISCONNECT PRECAUTIONS»(ref-164737-S10357055422004091500000) .

Note. ABS Control Module (w/EDL) -J104- is located under floor covering in front passenger's footwell.

Scheme 456

1. Remove bottom A-pillar trim. See «LOWER A-PILLAR TRIM, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/exteriorinterior-trim/#interior-trim__lower-a-pillar-trim-removing-and-installing) .
2. Remove floor covering.
3. Loosen screws securing ABS Control Module (w/EDL) -J104-.
4. Unplug connector from ABS Control Module (w/EDL) -J104-.
5. Install new control module in reverse sequence. Tightening torque of screws 9 Nm.
6. Enter radio code.

For non-codable control modules

Sender for rotation rate -G202- is located under floor covering in left front footwell.

It measures vehicle's rotation about vertical axis (yaw rate).

1. To remove floor covering, first push left front seat all the way back.
2. Remove bottom A-pillar trim, sill moulding and footrest. See «INTERIOR TRIM»(/audi/a6/c5-1997-2001/remont/exteriorinterior-trim/#interior-trim) .
3. Remove floor covering. Tightening torque for screw: 5 Nm

Scheme 457

Scheme 458

1. To remove floor covering, first remove driver's seat. See «FRONT SEATS»(/audi/a6/c5-1997-2001/remont/seats/#seats-frames__front-seats) .
2. Remove bottom A-pillar trim, sill moulding and footrest See «INTERIOR TRIM»(/audi/a6/c5-1997-2001/remont/exteriorinterior-trim/#interior-trim) .
3. Remove floor covering.

Tightening torque for screws: 5 Nm

Sensor for transverse acceleration -G200- and Sender for rotation rate -G202- for Bosch 5.3, removing and installing

Note. Sender for rotation rate -G202- may also be installed in a joint housing with Sensor for transverse acceleration -G200-.

Scheme 459

1. For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary.
2. Removing rear seat See «REAR SEATS»(/audi/a6/c5-1997-2001/remont/seats/#seats-frames) .
3. Item 2 sender is for rotation rate.

Sender for rotation rate -G202- is located underneath the driver's seat.

It measures the vehicle's rotation about the vertical axis (yaw rate).

Tightening torque of screws 5 Nm.

Sensor for transverse acceleration -G200

1. Item 3 Control module for ultra-sound sensors -J347

To remove sensor for transverse acceleration -G200-, first remove control module for ultra-sound sensors -J347-; see -arrows-.

Tightening torque of screws 2 Nm.

Scheme 460

Sensor for transverse acceleration -G200- following removal of control module for ultra-sound sensors -J347-.

Tightening torque of screws 2 Nm.

Scheme 461

The remaining installation steps are carried out in reverse sequence

1. Installing rear seat See «REAR SEATS»(/audi/a6/c5-1997-2001/remont/seats/#seats-frames) .
2. Enter radio code.

Sensor for transverse acceleration -G200- and sender for rotation rate -G202- for Bosch 5.7, removing and installing

Note. Sender for rotation rate -G202- is installed in a joint housing with Sensor for transverse acceleration -G200-.

1. For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary.
2. Removing rear seat See «REAR SEATS»(/audi/a6/c5-1997-2001/remont/seats/#seats-frames) .

The sender for rotation rate -G202- and the sensor for transverse acceleration are located under the rear seat bench.

It measures the vehicle's rotation about the vertical axis (yaw rate).

Scheme 462

1. Disconnect connector for ESP sensor

Tightening torque of screws 5 Nm.

The remaining installation steps are carried out in the reverse sequence

1. Installing rear seat See «REAR SEATS»(/audi/a6/c5-1997-2001/remont/seats/#seats-frames) .
2. Enter radio code.

Parking brake switch

Informs ABS control module (w/EDL) -J104- whether or not the parking brake is applied. This information is required because the parking brake influences the ESP control function.

The ABS solenoid valve relay -J106- and ABS return flow pump relay -J105- are no longer integrated in the ABS hydraulic unit -N55-, as in the Bosch type 5.0 system. They are now located in the relay carrier below the driver's-side storage compartment.

ABS/ESP Bosch 5.7, assembly overview

Note. The following list refers to items in (Scheme 464).

1. Bracket for hydraulic control unit Removing and installing, see «HYDRAULIC CONTROL UNIT, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
2. Vacuum pump for brake servo Only on gasonline engines in conjunction with an automatic transmission
3. ABS control module (w/EDL) - J104- The ABS hydraulic unit -N55- and the ABS control module (w/EDL) -J104- are J104- are combined to form the hydraulic control unit. Removing and installing, see «HYDRAULIC CONTROL UNIT, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
4. ABS hydraulic unit -N55- with ABS control module (w/EDL) -J104- The ABS hydraulic unit -N55- and the ABS control module (w/EDL) -J104- are combined to form the hydraulic control unit. Removing and installing, see «HYDRAULIC CONTROL UNIT, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
5. Sender 1 for brake booster -G201- Bolted onto hydraulic control unit Tightening torque 20 Nm
6. ABS hydraulic unit -N55- with ABS control module (w/EDL) -J104
7. Rotor for right-front speed sensor Checking, see «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__rotor-checking)
8. Right front ABS wheel speed sensor -G45- Removing and installing, see «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
9. Brake fluid level warning switch -F34
10. Instrument cluster
11. Anti-slip control switch - E132- Installation location: on the center console
12. Steering angle sensor - G85- for ESP Installation location: in the coil connector with slip ring on steering column Performing zero position compensation => VAS 5051 vehicle diagnostic, testing and information system
13. Parking brake warning light switch -F9- Installation location: on the parking brake lever assembly
14. Rotor for right-rear speed sensor Checking: See «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD), or «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD).
15. Right rear ABS wheel speed sensor -G44- Removing and installing: See «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD vehicles), or «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD vehicles).
16. Sensor for transverse acceleration -G200- and sender for rotation rate - G202- Installation location: underneath the radio Removing and installing, see «SENSOR FOR TRANSVERSE ACCELERATION -G200- AND SENDER FOR ROTATION RATE -G202- FOR BOSCH 5.7, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__sensor-for-transverse-acceleration-g200-and)
17. Left rear ABS wheel speed sensor -G46- Removing and installing: See «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD), or «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD).
18. Rotor for rear left speed sensor Checking: See «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (FWD), or «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) (AWD).
19. Traction control indicator light -K86- Installation location: in instrument cluster For further information refer to the owner's manual.
20. ABS warning light -K47- Installation location: in instrument cluster For further information refer to the owner's manual.
21. Warning light for brake system -K118- Installation location: in instrument cluster in driver information system For further information refer to owner's manual.
22. Brake light switch -F- Removing and installing brake light switch, see «ABS/ESP SYSTEM COMPONENTS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) Adjusting, see «ABS/ESP SYSTEM COMPONENTS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
23. Rotor for front left speed sensor Checking, «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__rotor-checking)
24. Left front ABS wheel speed sensor -G47- Removing and installing, see «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)

Scheme 463

Anti-lock brake system (ABS) Bosch 5.7

A traction control system (ASR) may also be installed as an optional extra on front wheel drive vehicles.

The ABS is split diagonally. The brake servo assistance is provided pneumatically by the vacuum brake servo unit.

Hydraulic unit -a- and control unit -b- form a single unit. It is therefore termed the hydraulic control unit.

The direct connection between these components reduces possible sources of malfunctions. There is no provision for repairing the hydraulic control unit - it must be replaced if faulty.

The bolts that connect the individual components of the hydraulic unit must not be slackened.

Scheme 464

Hydraulic unit and brake lines

The tightening torque for all brake lines on the Audi A6 is 15 Nm.

Note. The following list refers to items in (Scheme 466).

1. Brake master cylinder and brake servo
2. Brake line Brake master cylinder/primary piston circuit to hydraulic unit Tightening torque for connections at brake master cylinder and hydraulic unit: 16 Nm
3. Brake line Brake master cylinder/secondary piston circuit to hydraulic unit Tightening torque for connections at brake master cylinder and hydraulic unit: 16 Nm
4. Brake line Hydraulic unit to left-front brake caliper
5. Brake line Hydraulic unit to right-front brake caliper Tightening torque: 12 Nm
6. Brake line Hydraulic unit to right-rear brake caliper Tightening torque: 12 Nm
7. Brake line Hydraulic unit to left-rear brake caliper Tightening torque: 12 Nm
8. Sender 1 for brake booster -G201- Bolted onto hydraulic control unit
9. ABS hydraulic unit -N55- with ABS control module (w/EDL) -J104- Removing and installing, see «HYDRAULIC CONTROL UNIT, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
10. Locking clip
11. Buffer (4x)
12. Vacuum pump Not applicable
13. Buffer (1x)
14. Hex bolt, 10 Nm (3x)
15. Bracket

Scheme 465

Plug repair set, Part no. 1H0 698 311A

Brake pedal depressor; e.g. from V.A.G 1813

Installation location

The hydraulic control unit is installed on left side of engine compartment.

Scheme 466

1. For vehicles equipped with coded anti-theft radio, note radio code, obtain if necessary. See Caution under «GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__general-information-on-the-anti-lock-brake) before beginning repairs on the electrical system.
2. Disconnect battery. See «BATTERY DISCONNECT PRECAUTIONS»(ref-164737-S10357055422004091500000) .
3. Unlatch connector from control module in direction of -arrow- and unplug.
4. Insert brake pedal depressor between brake pedal and driver's seat. Depress the brake pedal by at least 60 mm.

Note. The brake pedal depressor must remain in position until all the brake lines have been reconnected to the hydraulic unit. Protect the engine compartment against escaping brake fluid.

Scheme 467

Scheme 468

1. Unscrew brake line connections on hydraulic unit.
2. Remove bolt -1- and pull it out in the direction of the arrow, and swing the coolant expansion tank to side. Tightening torque 6 Nm
3. Seal brake lines and threaded holes with plugs from repair kit Part No. 1H0 698 311 A.

Note. Protect the plenum chamber and the engine compartment against any escaping brake fluid.

Scheme 469

Scheme 470

1. Unscrew and remove lines -1-,-2- and -3-. (Scheme 470)
2. Detach brake lines -1- and -2- and seal with the dummy plug from repair kit Part No. 1H0 698 311 A.
3. Detach connectors -1-.
4. Unclip brake lines -2- from bracket.
5. Release the locking clip from below -1- and pull it out in the direction of the arrow.
6. Remove hydraulic control unit.

When installing, pay particular attention to the following points

Note. Only remove sealing plugs on new hydraulic control unit when the corresponding brake line is about to be installed. Brake fluid can escape, if the sealing plugs are removed too early, it can no longer be guaranteed that the unit is sufficiently filled or adequately bled.

1. Bleeding brake system, see «BLEEDING BRAKE SYSTEM»(/audi/a6/c5-1997-2001/remont/mechanical-hydraulic/#brake-system)
2. Enter radio code.

See Caution for connecting Telematics battery under GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM .

1. Connect battery ground strap. See «BATTERY DISCONNECT PRECAUTIONS»(ref-164737-S10357055422004091500000) .

ABS front axle components, removing and installing

Note. The following list refers to items in (Scheme 472).

1. Hex bolt Always replace Different versions, see part catalog Vehicle must not be raised when tightening this bolt. Tightening torque: See «AXLE SHAFTS - FRONT & REAR»(/audi/a6/c5-1997-2001/remont/axle-shafts/#axle-shafts-front-rear) .
2. Clamping sleeve Always replace Left and right sides are identical Before installing, grease the hole in the wheel bearing housing with lubricating paste G 000 650 Push into wheel bearing housing up to stop
3. Sealing collar
4. ABS wheel speed sensor Install drive axle before installing speed sensor. Push into clamping sleeve up to stop. Replacing, see «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
5. Drive axle with rotor Inspect rotor for signs of dirt and damage. See «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__rotor-checking) . Replace outer CV joint if the rotor is damaged. See «AXLE SHAFTS - FRONT & REAR»(/audi/a6/c5-1997-2001/remont/axle-shafts/#axle-shafts-front-rear) . Outer CV joint is supplied as replacement part with rotor.

Scheme 471

1. Loosen wheel bolts.
2. Raise vehicle.
3. Remove wheel.
4. Remove grommet -1- from the wheel housing. (Scheme 473)
5. Disconnect ABS wheel speed sensor harness connector -2-.
6. Disconnect ABS wheel speed sensor wiring from retainers (arrows).
7. Remove ABS speed sensor from wheel bearing housing.

Scheme 472

When installing pay particular attention to the following points

1. Replace clamping sleeve. See «ABS FRONT AXLE COMPONENTS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__abs-front-axle-components-removing-and) , item - 2 -.
2. Before installing speed sensor, install sealing collar.
3. Connect ABS wheel speed sensor wiring and fasten grommets into retainers.
4. Turn wheels completely to left and right stop positions and check ABS wheel speed sensor wiring clearance.

Rotor, checking

1. Remove wheel bolts.
2. Raise vehicle.
3. Remove wheel.
4. Remove ABS wheel speed sensor out of wheel bearing housing.
5. Inspect rotor for signs of damage or dirt.

Note. If rotor is damaged or dirty remove drive axle. If damage, replace outer CV joint together with rotor. See AXLE SHAFTS - FRONT & REAR . The outer CV joint is supplied with the rotor as a replacement.

ABS rear axle components, removing and installing (front wheel drive vehicles)

Note. The following list refers to items in (Scheme 474).

1. ABS wheel speed sensor Must be replaced when replacing new wheel bearing/hub unit. Removing and installing, see «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) Installation position, see «INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) Always replace O-ring and lubricate with brake cylinder paste G 000 650
2. Clip
3. Axle beam
4. Cover plate
5. ABS wheel speed sensor rotor Checking, see «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) Removing and installing, see «ABS WHEEL SPEED SENSOR ROTOR (FWD, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) If damaged or faulty replace together with wheel bearing/hub unit
6. Wheel bearing/hub unit Servicing See «SUSPENSION - FRONT»(/audi/a6/c5-1997-2001/remont/suspension-front/#suspension-front) . Replace wheel bearing/hub unit, and also replace ABS wheel speed sensor.
7. Hex socket-head bolt, 60 Nm
8. Brake disc

Scheme 473

1. 80-200 pry lever

Scheme 474

Scheme 475

1. Lift rear seat bench out of locking mechanism.
2. Disconnect ABS wheel speed sensor harness connector and push out grommet (arrow).
3. Raise vehicle.
4. Disconnect ABS wheel speed sensor wiring from retainers (arrows).
5. Remove retainer for ABS wheel speed sensor.
6. Pry ABS wheel speed sensor from wheel bearing/hub unit using 80-200 pry lever.

Scheme 476

Scheme 477

1. Before inserting ABS wheel speed sensor, lubricate circumference of seal with brake cylinder paste.
2. Insert ABS wheel speed sensor -1- until stop. (Scheme 478)
3. Locating tab -A- faces front on left and rear on right.
4. Push ABS wheel speed sensor into wheel bearing housing by hand.
5. Insert retainer for ABS wheel speed sensor.

Note. When routing the ABS wheel speed sensor wiring note the following

Scheme 478

Scheme 479

1. Route ABS wheel speed sensor wiring -1- next to brake line -2- on both sides as shown.
2. On the left side, maintain a clearance of about 2 cm between the heat shield on the exhaust system and ABS wheel speed sensor wiring.
3. On right-hand side, ABS wheel speed sensor wire -1- must be routed between fuel lines -2-.

1. 80-200 pry lever

Scheme 480

1. Raise vehicle.
2. Pry ABS wheel speed sensor from wheel bearing/hub unit using 80-200 pry lever.
3. Inspect ABS wheel speed sensor rotor for dirt and damage through mounting hole of wheel speed sensor. If ABS wheel speed sensor rotor is damaged or dirty, replace rotor together with wheel bearing/hub unit together.
4. Install ABS wheel speed sensor.

Note installation position. See INSTALLING .

1. 80-200 pry lever

Scheme 481

Scheme 482

1. Remove wheel bolts.
2. Raise vehicle.
3. Remove wheel.
4. Remove bolts -A- and use wire to support brake caliper housing to body. (Scheme 482)
5. Remove retainer for ABS wheel speed sensor.
6. Pry ABS wheel speed sensor from wheel bearing/hub unit using 80-200 pry lever.
7. Remove socket-head bolts from wheel bearing/hub unit and remove wheel bearing/hub unit with backing plate.

If ABS wheel speed sensor rotor is damaged or dirty, replace rotor together with wheel bearing/hub unit.

1. Install new wheel bearing/hub unit and backing plate to axle beam and tighten to 60 Nm.
2. Insert brake disc.
3. Mount brake caliper to axle beam and tighten to 95 Nm.
4. Install ABS wheel speed sensor.
5. Note installation position. See «INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) .
6. Insert retrainer for ABS wheel speed sensor.

ABS rear axle components, removing and installing (all wheel drive vehicles)

Note. The following list refers to items in (Scheme 484).

1. Hex bolt Always replace Vehicle must not be raised when tightening this bolt. Tightening torque: See «AXLE SHAFTS - FRONT & REAR»(/audi/a6/c5-1997-2001/remont/axle-shafts/#axle-shafts-front-rear) .
2. Clamping sleeve Always replace Left and right side are identical Before installing coat hole in the wheel bearing housing with brake cylinder paste G 000 650 Push into wheel bearing housing up to stop
3. ABS wheel speed sensor Push into clamping sleeve up to stop Replacing, see «ABS WHEEL SPEED SENSOR, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs)
4. Drive axle with ABS wheel speed sensor rotor (all wheel drive) Check rotor for dirt and damage. See «ROTOR, CHECKING»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs) . Replace outer CV joint if the rotor is damaged. Outer CV joint is supplied with ABS wheel speed sensor rotor as replacement part.

Scheme 483

1. Switch off ignition.
2. Lift rear bench seat out of locking mechanism.
3. Disconnect ABS wheel speed sensor harness connectors and push out grommet (arrow).
4. Raise vehicle.
5. Pull ABS wheel speed sensor out of wheel bearing housing.
6. Disconnect ABS wheel speed sensor wiring from retainers.
7. Remove ABS wheel speed sensor wiring downward together with grommet.

Scheme 484

1. Replace clamping sleeve. See «ABS REAR AXLE COMPONENTS, REMOVING AND INSTALLING (ALL WHEEL DRIVE VEHICLES)»(/audi/a6/c5-1997-2001/remont/anti-locktraction-control/#brake-system-abs__abs-rear-axle-components-removing-and) item - 2 -.
2. Connect ABS wheel speed sensor wiring and snap grommets in retainers.

1. Loosen wheel bolts.
2. Raise vehicle.
3. Remove wheel.
4. Remove ABS wheel speed sensor out of wheel bearing housing.
5. Check rotor for damage or dirt.

Note. If ABS wheel speed sensor rotor is damage or dirty, remove axle arm or drive axle. If damaged, replace outer CV joint together with ABS wheel speed sensor rotor. Axle arm and outer CV joint are supplied with ABS wheel speed sensor rotor as a replacement part.

See also:
• EMERGENCY BATTERY, SWITCHING OFF/ON
• ON BOARD DIAGNOSTIC (OBD)
• BLEEDING BRAKE SYSTEM
• DRIVER'S STORAGE COMPARTMENT, REMOVING
• BASIC SETTING (SCAN TOOL FUNCTION 04)
• LOWER A-PILLAR TRIM, REMOVING AND INSTALLING
• INTERIOR TRIM
• FRONT SEATS
• REAR SEATS
• AXLE SHAFTS - FRONT & REAR
• SUSPENSION - FRONT
• HYDRAULIC PUMP FOR ELECTRONIC STABILIZATION PROGRAM (ESP), REMOVING AND INSTALLING
• ROTOR, CHECKING
• SENSOR FOR TRANSVERSE ACCELERATION -G200- AND SENDER FOR ROTATION RATE -G202- FOR BOSCH 5.3, REMOVING AND INSTALLING
• GENERAL INFORMATION ON THE ANTI-LOCK BRAKE SYSTEM
• BRAKE LINE CONNECTIONS: HYDRAULIC CONTROL UNIT WITH ESP HYDRAULIC PUMP
• ELECTRONIC STABILZATION PROGRAM (ESP) HYDRAULIC UNIT, SERVICING
• ABS FRONT AXLE COMPONENTS, REMOVING AND INSTALLING
• ABS REAR AXLE COMPONENTS, REMOVING AND INSTALLING (ALL WHEEL DRIVE VEHICLES)