Anti-Lock Brake System (Abs) Repair Instructions

The Anti-lock Brake System (ABS) is divided diagonally (two circuits). The vacuum brake servo unit boosts the brakes pneumatically.

Vehicles with Anti-lock Brake System (ABS) Mark 60 or Anti-lock Brake System (ABS) Mark 70 do not have a mechanical brake pressure regulator. A specially coordinated software program inside the ABS Control Module -J104- determines brake pressure allocation at the rear axle.

Anti-lock Brake System (ABS) malfunctions do not affect the brake system and the booster. Conventional brake system stays operative even without Anti-lock Brake System (ABS). A change in braking behavior should be checked. After the Anti-lock Brake System (ABS) Warning Lamp -K47- turns on, the rear wheels may lock prematurely when braking!

Fig 1: Configuration

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

1. ABS Hydraulic Unit -N55- with ABS Control Module -J104-
2. Brake booster with tandem brake master cylinder

The Anti-lock Brake System (ABS) Control Module -J104- -1- and ABS Hydraulic Unit -N55- -2- are a single unit. Separation can only be performed when removed from vehicle. The hydraulic pump -3- must not be separated from the ABS Hydraulic Unit -N55-.

Fig 2: Identifying Control Module, Hydraulic Unit And Hydraulic Pump

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

Separation cannot be performed on vehicles with hydraulic brake booster or hill assist.

• First determine the cause of the damage and then get the coding from the Anti-lock Brake System (ABS) Control Module -J104- using the Vehicle Diagnostic Tester before performing any service work on the anti-lock braking system.

• Turn off the ignition and disconnect the battery ground cable.
• Before welding with an electric welding tool, pay attention to the notes found here. Refer to appropriate service information .
• When working with brake fluid, observe relevant safety precautions and notes.
• After finishing any work that required opening the brake system, bleed the brake system using the Brake Charger/Bleeder Unit VAS5234.
• During final road test, carry out at least one Anti-lock Brake System (ABS)-controlled braking operation (appropriate pulsations must be felt at brake pedal).
• It is necessary to maintain a high level of cleanliness when working on the Anti-lock Brake System (ABS) system.
• Do not use any products containing 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 the removed parts on a clean surface and cover them.
• Use the valve body transportation protection after disconnecting the Anti-lock Brake System (ABS) Control Module -J104- and the ABS Hydraulic Unit -N55-.
• Carefully cover over opened components or seal, if repairs are not performed immediately (use Sealing Plugs 1H0 698 311 A).
• Only use lint-free cloths.
• Only unpack replacement parts immediately prior to installation.
• Only use parts in their original packaging.
• When the system is open do not work with compressed air or do not move the vehicle.
• The Anti-lock Brake System (ABS) Control Module -J104- may be briefly exposed to a maximum temperature of 95°C when painting.
• The Anti-lock Brake System (ABS) Control Module -J104- may be exposed to a maximum temperature of 85°C for approximately 2 hours.
• Make sure that brake fluid does not enter harness connectors.

For the Anti-lock Brake System (ABS)-Mark 60 EC in this vehicle, the Transverse Acceleration Sensor -G200-, the Rotation Rate Sensor -G202- and the Longitudinal Acceleration Sensor -G251- (depending on the vehicle equipment level) are installed in the Anti-lock Brake System (ABS) Control Module -J104-.

It is not possible to replace them individually.

-- Anti-lock Brake System (ABS) Control Module -J104-, removing and installing. Refer to ABS Control Module -J104- AND ABS Hydraulic Unit -N55- WITH 4-CYLINDER GASOLINE ENGINE AND ABS MARK 60 EC ABS/EDL/ASR/ESP .

Vehicles without Electro-Mechanical Power Steering

The Steering Angle Sensor -G85- is installed on the steering column. Refer to Steering Angle Sensor -G85- ON STEERING COLUMN .

Steering Angle Sensor -G85-, removing and installing at the steering column. Refer to REMOVAL AND INSTALLATION .

Vehicles with Electro-Mechanical Power Steering

The Steering Angle Sensor -G85- is located in the steering gear. Refer to REMOVAL AND INSTALLATION .

The Steering Angle Sensor -G85- cannot be replaced separately.

Use the Vehicle Diagnostic Tester for fault diagnostics.

Steering Angle Sensor -G85-, removing and installing. Refer to REMOVAL AND INSTALLATION .