Electronic Brake Control Module: Service and Repair
ABS Hydraulic Unit with ABS Control Module
Special tools, testers and auxiliary items required
• Brake pedal actuator (V.A.G 1869/2)
• Vehicle diagnosis, testing and information system (VAS 5051B) or (VAS 5052)
• The ABS Hydraulic Unit (N55) and ABS Control Module (J104) are located in the front of the luggage compartment.
• The ABS hydraulic unit and ABS control module form a unit.
CAUTION!
The ABS control module and ABS hydraulic unit must not be separated.
Removing
- Read the control module version and make a note of it.
- Disconnect the battery, noting the radio code.
- Insert the (V.A.G 1869/2) between the brake pedal and driver seat by pressing the brake pedal down at least 60 mm.
- Connect the hose from a bleeder bottle to one of the bleeder screws on the left front caliper.
- Connect the hose from a bleeder bottle to one of the bleeder screws on the left rear caliper.
- Open the bleeder screws on the left front and rear brake calipers to reduce the pressure in the ABS hydraulic unit.
- Close the left front and left rear bleeder screws.
• Do not remove (V.A.G 1869/2).
- Remove the luggage compartment liner in the front area of the luggage compartment.
- Release and disconnect the connector on the control module - 1 -.
• Make sure that no brake fluid enters control module connector housing. This could lead to corrosion of the contacts and thereby cause the system to fail.
• A contaminated connector housing must be carefully cleaned with compressed air.
- To protect against escaping brake fluid, place a lint-free rag in the area under the control module and hydraulic unit.
- Mark the brake lines for installation later.
CAUTION!
Do not bend or kink the brake lines.
- Remove the brake lines from the ABS hydraulic unit and brake master cylinder.
- Remove the remaining brake lines - arrows - from the ABS hydraulic unit.
- Open brake line bracket - 1 -.
- Seal brake lines and threaded holes with plugs from repair kit.
- Loosen the two hex nuts - 1 - on the buffers.
- Carefully remove the ABS hydraulic unit together with the ABS control module upward from the console rubber buffers.
CAUTION!
Excessive shaking (e.g. dropping, impact) may destroy the control module. Control module must then no longer be used.
- Set the hydraulic unit with the control module down on a clean, level surface.
• Seal the threaded holes and brake lines with plugs after removing the ABS control module and ABS hydraulic unit.
CAUTION!
The hydraulic pump must not be separated from the hydraulic unit.
Installing
Installation is the reverse of removal, with special attention to the following:
• For customer service, the hydraulic unit is filled with brake fluid.
• Remove the sealing plugs on the new hydraulic unit when the corresponding brake line is going to be installed.
• If the sealing plugs are removed from the hydraulic unit before installing the corresponding brake line, the brake fluid will drain. If that is the case, sufficient brake system bleeding can no longer be ensured.
- Connect the brake lines according to the markings.
1 To right front brake caliper
2 To left rear brake caliper
3 To right rear brake caliper
4 To left front brake caliper
5 To primary piston circuit
6 To secondary piston circuit
CAUTION!
If the brake line connectors are replaced, an ABS/ESP system malfunction will register.
• By performing the output check diagnosis, it can be determined if the line connections were interchanged.
- Tighten all the brake lines on the hydraulic unit.
- Connect the connector on the control module.
- Remove (V.A.G 1869/2).
- Bleed brake system. Refer to => [ Brake System, Bleeding ] Brake System, Bleeding.
- Install the luggage compartment liner in the front of the luggage compartment.
- After securing the brake lines on the hydraulic unit, perform output diagnostic test mode.
• By performing the output check diagnosis, it can be determined if the line connections were interchanged.
If ABS hydraulic unit was replaced, it must be coded.
Use the (VAS 5051B) or (VAS 5052) for this.
- On display, select:
• Chassis
• Brake System
• 01- On Board Diagnostic (OBD) capable systems
• 03 - Brake electronics
- Select the following functions on the display:
• ABS/ASR/ESP control module
• ABS/ASR/ESP control module, functions
• J104 Coding control module
The following sensors should also be calibrated after replacing control module:
• Steering angle sensor
• Transverse acceleration sensor
• Longitudinal acceleration sensor
• Brake pressure sensor 1
Use the (VAS 5051B) or (VAS 5052) for this:
- On display, select:
• Chassis
• Brake System
• 01- On Board Diagnostic (OBD) capable systems
• 03 - Brake electronics
- Select the following functions on the display:
• ABS/ASR/ESP control module
• ABS/ASR/ESP control module, functions
- Then perform the ESP driving and system test.