Anti-Lock Brake System: Description

The Mercedes-Benz Anti-Lock Brake System (ABS) operates from the interaction of a hydraulic unit with 3 fast-switching solenoid valves, 3 speed sensors, an electronic control unit with overvoltage protection and a wire harness with relays.

A Yellow warning lamp with ABS symbol, on instrument panel, lights as the ignition is switched on. The ABS warning lamp will go out once the engine is running. The ABS system is programmed to activate above 7.5 MPH.

When vehicle speed is above 3 MPH, Built-In Test Equipment (BITE) will begin check of ABS. If any fault is found, the warning lamp will again light. When warning lamp lights, ABS is switched off and vehicle will brake without ABS control. The conventional brake system remains operational.

If battery is below 10.5 volts, when ignition is turned on and test speed exceeded, ABS will remain off until alternator increases voltage to above 10.5 volts. Warning light will then go out.

Following repair, during which no direct components of ABS were involved, a simple light test will check system. Check lamp goes out above 7 MPH.

NOTE: The entire ABS system must be checked if repair includes any ABS component or if units are replaced following an accident. Use Bosch Tester Model ETT016.00 (Part No. 0084 101 600) together with brake test bench (chassis dynamometer).