Fault Indication / Troubleshooting

Fault indication / Troubleshooting

Important notes

If warning displays and faults are shown in the PDAS/ABS or other fault memories, they may have been triggered off by the following interference:

- Interference to electronic components or the car's electrical system caused by the ignition current or sparks at gaps in the ignition circuit (incorrectly assembled or loose spark plug caps or damaged ignition leads).

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


Troubleshooting aids

When measuring with the multimeter at the control-unit plug, make up 1 or 2 temporary 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.


Exchanging assemblies

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

Locking valve block: After installing/bleeding, carry out a check on the front-rear and lateral differential locks to ensure that the connections have not been accidentally interchanged.


Combined plug connections - distinguishing between wires




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

Screened wires (1) for the speed sensors. 2 wires with a protective tube (2) for brake pad wear.


Trial drive after eliminating fault

Erase the contents of the fault memory after the fault has been eliminated. Try the car out, then read out the fault memory again.