Test Point 10

DTC 31

Front Left ABS Valve

Certain faults in the ABS valve area (short circuit to plus or short circuit to ground in a control wire) can also be shown as a valve relay fault by the 9288 System Tester.

A fault in the ABS valve circuits is normally stored as an ABS valve fault in the DTC memory of the control unit. When the DTC memory is read out, it is possible in the above situation for two faults to be displayed (ABS valve and valve relay).





1. Switch off the ignition and pull the plug off the control unit. Check PIN 19 of plug to PIN 17 and to PIN 23 for continuity.

If necessary, interrupt the circuit (plug at hydraulic unit) and localize the discontinuity by reference to the wiring diagram.





2. Pull off the valve relay (7-pole) at the hydraulic unit. Check for a short circuit to plus or to ground in the circuit as described in point 1 by measuring at PIN 19.

If a fault is detected, interrupt the circuit as described in point 1 in order to localize the incorrect short-circuit to plus or to minus.

3. Check resistance between PIN 19 of the plug and terminal 30 at the valve relay.

If nominal value is obtained: proceed with point 4.

If nominal value is not obtained:

- Pull off the 12-pole plug at the hydraulic unit.

- Check internal resistance of the ABS solenoid valve. Measure between PIN 1 and PIN 4 (at the hydraulic unit).

- Nominal value 0.7...1.7 Ohms. If nominal value is incorrect: replace the hydraulic unit.

4. Check whether the valve relay is energized (voltage is present at the solenoid valves). To make this check, connect all plugs and the relay. Push back the protective tube on the transverse lock valve plug (in the wheel housing at the rear left).

Switch the ignition off, then on again.

Battery voltage must be present at the black wire. If no voltage is present: continue with DTC 34 (valve relay). Comply with the testing notes

If voltage is present, try replacing the PSD/ABS control unit (output stage defective).

Testing notes

If a voltage supply plug to the solenoid valves (ABS valves or differential lock) is pulled off while the ignition is switched on, the valve relay will be de-energized. It is not re-energized when the plug is reconnected until the ignition has been switched off and on again.