Preliminary Information

Important Notes

If warning displays light up and/or faults are shown in the DTC memory of the PSD/ABS, they may also have been triggered by the following problems:

- Control unit supply voltage less than 9.5 volt (undervoltage).

- Control unit plug disconnected.

- Contact resistance caused by poor ground connections, leading to differences in potential or inadequate shielding of speed sensors. The poor ground connection may not only occur at the affected components, but also at other important grounding points.

- Important: The warning "PSD off" may appear in the display fields of the instrument cluster, even though no fault is stored in the DTC memory. Check the lock hydraulics (lock operation) in this case, Check Lock Hydraulics

Troubleshooting Aids

When measuring with the multimeter at the control-unit plug, make up 1 or 2 auxiliary leads in your own workshop, each with 2 flat pin plugs No.17.457.2, to avoid damaging the plug contacts in the control-unit plug during the test.

Combined Plug Connections - Distinguishing Between Wires

In the brake pad wear, speed sensor and HF sending unit wiring there are several combined plug connections of similar pattern. In this area, the wires can be distinguished as follows:

- Shielded wires for the speed sensors and HF sending units.

- 2 wires with a protective tube for brake pad wear.

- One pin and one socket exist on the HF sending unit plug connections. The speed sensor plug connections possess 2 pins as well as 2 sockets on the opposite side.





- Two combination connectors are located one above the other in the spare tire area. The wires are identified there with L = rear left and R = rear right.

Replacing The Hydraulic Unit

After installing/bleeding the ABS hydraulic unit, carry out a complete ABS test with the ABS 2-LED tester.

Test-Drive After Eliminating The Fault.

Clear the DTC memory after eliminating the fault. Perform a test drive and then read out the DTC memory again.

If necessary (e.g. in the case of a fault in the speed sensors), also clear the DTC memory of the RDK control unit.