Corrective Actions

If a malfunction or problem has been detected or reported, perform guided troubleshooting:
- First switch on the ignition, and note whether the indicator lamps light up. Refer to "Overview of indicator lamp functions, see the The tables for the relevant system facilitates an initial diagnosis.
- Fulfill test requirements.
- Connect the VAG1551 Scan Tool (ST) and select the address word 03 "Brake Electronics".
- Check the control module version, Refer to Parts Supplier and press the (arrow) button.
- Check DTC memory. If a DTC is stored: Note the DTC and erase DTC memory.
- End data transfer using the "End Output" function.
- Repair the malfunction with the help of the DTC table. Select again the address word 03 "Brake Electronics". Check and erase DTC memory.
- End data transfer using the "End Output" function. Disconnect VAG 1551 Scan Tool (ST).
- Make sure all harness connectors are connected and engaged. Perform a road test. The indicator lamps must not light up during the drive. If the indicator lamps light up during the road test, repeat the troubleshooting procedure.

Note: If the control module connector is disconnected during the drive, an unfounded DTC may be stored in the memory of another control module. The brake system will only be partially functional. Because brake pressure at the rear wheels is no longer regulated vie Electronic Brake Distribution (EBD), the rear wheels tend to brake excessively. This causes the rear of the vehicle to break loose. Driving the vehicle presents the risk of accident.

- Always switch off ignition before carrying out installation or repair work.
- Only replace a malfunctioning component if you are certain that all electrical wires to this component are functioning properly. The lines must work properly and be capable of carrying all signals without any problems. Check the lines for the following:
- Corrosion or loose connections in the connectors or Ground straps. If there are bent, broken, or corroded contacts on the connectors, replace the contacts using VAS1978 wiring harness repair kit.
- Open circuit in wiring
- Short circuits to B+ or Ground (GND)
- Welding work performed with electrical welding equipment can affect the ABS/ESP system.

Test requirements
- Vehicle equipped with approved wheel and tire sizes, which must be the same on all four wheels. All tire inflation pressures checked according to specification.
- The mechanical/hydraulic components of the brake system are OK. Hydraulic connections and lines are sealed properly (visual check at hydraulic unit, brake calipers, wheel cylinders, tandem master brake cylinder).
- Wheel bearings and wheel bearing play OK
- Wheel speed sensors installed correctly
- Supply voltage OK (at least 10.0 volts).
- Harness connector is properly connected at ABS control module -J104-, locking mechanism is engaged.
- The OBD sequence can only be started with the vehicle stationary and the ignition switched on (or with the engine running). It is not possible to initiate On Board Diagnostic (OBD) once wheel speed has reached 2.75 km/h.
- While testing the ESP system, make sure that the vehicle's electrical system is not subjected to electromagnetic interference; keep the vehicle away from equipment with a high current draw such as electric welding units.

WARNING: The diagnostic will not terminate at a speed of v = 20 km/h. Risk of accident!