Electronic Brake Control Module: Service and Repair

ABS Control Module and Hydraulic Unit

Special tools, testers and auxiliary items required

• Torque wrench (V.A.G 1331)

• Torque wrench (V.A.G 1410)

• Brake pedal actuator (V.A.G 1869/2)

Removing

Component location:

The ABS control module (J104) is bolted to the hydraulic unit and is located at left in engine compartment.

CAUTION!
Do not bend brake lines near the hydraulic unit!

- Note radio code (for vehicles equipped with coded anti-theft radio).

- Disconnect battery.

- Disconnect intake air duct - 1 - and connector - 2 - from Mass Air Flow (MAF) sensor (G70).





- Remove bolts - 3 -, - 4 - and - 5 -.

- Remove complete air filter.

- If present, remove protective housing for relay from cable channel.

- Draw as much brake fluid as possible from brake fluid reservoir using a bleeder bottle.

- Disengage connector - arrow 1 - and disconnect - arrow 2 - from control module.





- Insert brake pedal actuator (V.A.G 1869/2 ).

- Attach bleeder bottle bleeder hose to left front and right rear brake caliper bleeder screw and open bleeder screws.

- Operate brake pedal using brake pedal actuator at least 60 mm.

- Close left front and right rear bleeder screws.

- Do not remove brake pedal actuator (V.A.G 1869/2 ).

- Place a sufficient number of lint-free cloths under control module and hydraulic unit.

CAUTION!
Make sure that the brake fluid does not come in contact with the terminals.

- Remove brake lines from ABS hydraulic unit (N55 ) - 1 - to master brake cylinder and tie up.





- Remove remaining brake lines from ABS hydraulic unit (N55).

- Seal brake lines and threaded bores using plugs from repair set (1H0 698 311 A).

- Remove bolts - arrows - from bracket for control module/hydraulic unit.

- Remove ABS hydraulic unit (N55) together with ABS control module (J104).

Control Module, Removing from Hydraulic Unit

- Place hydraulic unit with control module on a clean and flat surface on the floor.

- Remove inner Torx bolts E 5 - arrows - from ABS control module (J104) and remove ABS hydraulic unit (N55).





CAUTION!
The hydraulic pump must not be separated from the hydraulic unit.

- Carefully disconnect hydraulic unit with hydraulic pump upward at interface - 1 - from control module.

When removing control module, be sure that the valve domes of the hydraulic unit do not jam or get bent in the magnetic coils of the control module.





Cover control module magnetic coils with a lint free cloth.

Use transport protection for valve domes after disconnecting from control module and hydraulic unit.

The dome, supplied for the control module as a replacement part, can only be clipped once and not be removed.

Installing

• Do not remove sealing plugs at new hydraulic unit until 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.

• When attaching control module and hydraulic unit, be sure that the valve domes of the hydraulic unit do not jam or get bent in the magnetic coils of the control module.

- Bolt control module to hydraulic unit using new bolts. Note tightening specification: max. 4 Nm.

- Bolt ABS unit to bracket.

Do not tighten bolts completely. It will be easier to attach the various brake lines to the hydraulic unit.

- Tighten hydraulic unit after tightening brake lines.

- Rest of installation is in reverse order of removal.

- Remove brake pedal actuator (V.A.G 1869/2 ).

- Bleed brake system => [ Brake System Bleeding General Information ] Brake System Bleeding General Information.

- Code radio.

- Code control module.