Troubleshooting and Testing Requirements

WARNING:
^ ABS is a safety system; ABS diagnosis and repair requires specialized training and knowledge of the system.
^ Always check Diagnostic Trouble Code (DTC) memory before beginning any work on the ABS system.
^ Do not drive the vehicle while the harness connector is disconnected from the ABS control module.
^ Do not drive with the VAG 1710 ABS tester connected
^ Always switch the ignition off when disconnecting or connecting ABS harness connectors.
^ Fasteners on the ABS hydraulic unit must not be loosened (except for the cover screw, for access to the relays for the return pump and solenoid valves).
^ Follow all the usual safety precautions when working with brake fluid.
^ ABS malfunctions are indicated by the ABS warning light, certain malfunctions are recognized only when vehicle speed exceeds 12 km/h (7 mph)
- Always road test.

General Troubleshooting
This section describes troubleshooting with ABS tester VAG1710 and VAG1710/1 adapter or equivalents.
- Using the VAG1710 ABS tester, the system can be tested in 6 test steps without the need of a brake dynamometer.
- The coding switch in the VAG1710/1 adapter cable adjusts the ABS tester to model-specific wiring.
- The ABS control module is equipped with DTC memory; check DTC memory as the first step in any ABS troubleshooting.
- Test step "5" requires the help of a second technician.
- Before replacing components, make sure that the electrical connections are OK.
- Do not repair faulty ABS components. Replace components only, if necessary.


Electrical Troubleshooting
- Troubleshooting according to this program is basically complete and should be followed in the sequence described here.
- If one malfunction is found and repaired, repeat the complete troubleshooting procedure again.
- When repairing malfunctions, only malfunctioning components are identified. Removal and installation procedures are described in the corresponding Repair Groups.
- Locate faulty wiring according to the applicable wiring diagrams, and repair as necessary.
- For component locations refer to applicable wiring diagrams.

Required Vehicle-specific Technical Information Sources
Wiring diagrams

Special Tool Requirements
- VAG 1551 scan tool or equivalent
- VAG1710 ABS tester with VAG1710/1 adapter cable or equivalent
- Digital multimeter (Fluke 83 or equivalent)
- VAG1598 test box and VAG1598/03 adapter or equivalent
- VW1594 connector test kit or equivalent

Test Requirements
- Specified tire size
Same size and tread pattern on all four wheels
Tires inflated to correct pressures
- Battery positive voltage (B+) over 10.5 volts
- Generator (GEN) warning light -K2- goes out after engine starts
- Generator drive belt condition and tension OK
- Conventional brake system functioning properly, including brake light switch, brake lights, brakes pads, etc.
- No leaks from hydraulic connections or lines (visually inspect ABS hydraulic unit, brake calipers, etc.; fluid level OK)
- Ground connection for ABS return flow pump OK (make sure connection is secure; check for corrosion)
- Wheel bearings and wheel bearing play OK