Anti-Lock Brake System Repair Information

• Before carrying out repair work on the Anti-lock Brake System (AB) (, determine the cause of the malfunction using "Guided Fault Finding".

"Guided Fault Finding" is performed using the vehicle diagnosis, testing and information system VAS 5051.

• Before working on the ABS, disconnect the battery ground (GND) cable. If the vehicle has a coded radio, obtain the code before disconnecting the battery.
• When working with brake fluid, observe relevant safety precautions and notes, refer to BRAKE SYSTEM BLEEDING .
• After finishing any work that required opening the brake system, bleed the brake system using the brake charger/bleeder unit VAS 5234 or V.A.G 1869. Refer to BRAKE SYSTEM BLEEDING .
• During the final road test, carry out at least one ABS controlled braking operation (appropriate pulsations must be felt at brake pedal).
• Absolute cleanliness is required when working on the ABS. 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 or seal opened components, if repairs are not carried out immediately. (Use the plugs 1 H0 698 311 A)
• Only use lint free cloths.
• 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 the vehicle while the system is open.
• Make sure that brake fluid does not enter harness connectors.
• When painting, electronic control modules 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 (approximately 2 hours).