Antilock Brake System (ABS)

Antilock Brake System (ABS)


The anti-lock brake system is generally maintenance-free.

Testing, assembly, and repair work may only be performed by qualified personnel.

By not observing the points described in the repair manual, the system can be damaged and vehicle safety could be compromised.

• Before performing repair work on the anti-lock brake system, determine the cause of the malfunction using On-Board Diagnostics (OBD).

• When installing a new hydraulic control unit, use the vehicle diagnostic tester (VAS 5051B) or (VAS 5052) to check the coding.

• Switch ignition off before installation work. If the radio in the vehicle is coded, find out the radio code before disconnecting the battery ground cable.

• When working with brake fluid, observe relevant safety precautions and notes, refer to => [ Brake Fluid ] Description and Operation.

• Bleed the brake system with the brake charger/bleeder unit (VAS 5234) for all work that requires opening the hydraulic system. High and low pressure testing should also be performed on the brake system, refer to => [ High and Low Pressure Testing ] High and Low Pressure Testing.

• During the final road test, ensure that a ABS-controlled brake test is performed at least once (pulsation must be felt at the brake pedal). refer to the vehicle diagnostic tester (VAS 5051B) or (VAS 5052).

• Absolute cleanliness is required when working on the anti-lock 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 or seal open components, if repairs are not carried out immediately. Use the plug from repair set 1H0 698 311 A.

• Only use lint-free cloths.

• Only unpack replacement parts immediately prior to installation.

• Only use Original Parts still in their original packaging.

• Do not work with compressed air and do not move vehicle while the system is open.

• Make sure brake fluid cannot get into the connector.