Function

Anti-Lock Brake System with Electronic Differential Lock ABS/EDL Bosch 5.0

Function
The On Board Diagnostic (OBD) function relates to the electrical and electronic parts of the ABS system; i.e. it can only recognize malfunctions (e.g. interruption of a wheel speed sensor) via the electrical connection to the control module.

The 40-pin ABS control module (w/EDL) -J104- forms a compact unit with the hydraulic unit. The unit is located on the left-hand side of the engine compartment. The control module is equipped with DTC memory. The connection for On Board Diagnostic (OBD) is located at left, below the switch for rear window defrost.

When malfunctions occur in monitored sensors or components, a maximum of 3 Diagnostic Trouble Codes (DTCs) can be stored, sometimes with a description of the malfunction type. ABS regulation is then shut off in the control module and the ABS Warning Light -K47 lights up. The traditional brake system remains effective.

Sporadically occurring (periodic) malfunctions are also recognized and stored as DTCs. If this malfunction does not occur again within 50 vehicle starts and driving procedures, it will be erased from DTC memory, except for the malfunction "control module faulty". (malfunction removal counter)

After ignition is switched on and/or engine is started, the ABS Warning Light -K47- lights up for approximately 2 seconds.

A test sequence (self-test) is performed in the control module during this time, with the functions:
^ Supply voltage is tested, minimum 10.0 volts
^ Control module and valve coils are checked
^ A static wheel speed sensor test is performed (without speed signal).
^ If, after reaching approximately 30 km/h, it is determined that the speed signal is not OK, the ABS Warning Light -K47- lights up again.

VAG1551 Scan Tool (ST) or VAS5051 tester
Always initiate On Board Diagnostic (OBD) to start troubleshooting. Electrical malfunctions that affect braking are stored in DTC memory. They can be recognized using the VAG1551 Scan Tool (ST) or the VAS5051 tester.

The indicated diagnostic data leads to a DTC table with notes regarding potential malfunction causes and specific repair procedures.