Test 23/Fault Code 39
Test point 23Valve relay Open circuit / short to ground / short to positive
Fault code 39
System Tester 9288 can be used to check if the solenoid valve has picked up or dropped out. Select solenoid valve relay in the Actual values menu. The following Tester display then appears: Valve relay tightened (picked up) or released (dropped out). Specified display: Valve relay tightened.
If connectors or the solenoid relay have been disconnected, switch off the ignition before running the checks and then switch the ignition on again as the (solenoid) relay otherwise cannot pick up.
The valve relay may also have dropped out if another system fault is present at the same time (ABS valve fault).
1. Pull off valve relay (R68INO.2). Release the relay holder (press out body-bound rivet No.3) to allow the relay cover to be removed. Check that connectors engage correctly in relay base (may have partially slipped down out of base). Check if voltage (approx. 12 volts) is present at relay base terminal 30 (system voltage). Check 60A fuse and wire from relay base to fuse if required.
2. With the valve relay pulled off, jumper relay terminals 30 and 87. Use System Tester in ,,Actual values" menu to select the valve relay and check if tester displays the "Valve relay tightened" (picked up) message.
Display "Valve relay tightened": Proceed with step 3.
Display "Valve relay not tightened": Proceed with step 5.
3. Check if system voltage is present at terminal 86 of relay base (approx. 12 volt) when ignition is switched on. If required, check wire between control unit connector PIN 2 and relay base terminal 86.
4. Replace valve relay on a trial basis or use the pump return relay (identical component) for this check. Then erase the fault memory and use the "Static test" menu to check if the fault has been remedied. If the fault is still present, pull off control unit connector with the ignition switched off and check the control circuit (wires once with valve relay connected and once without valve relay if required) according to wiring diagram for open circuit, short to ground and short to positive.
5. Pull off connector from hydraulic unit (pull slide upwards). Check wire between connector PIN 15 and valve relay base terminal 87 (valve relay pulled off) for open circuit, short to ground and short to positive.
6. Measure resistance between valve relay base terminal 87 (relay pulled off) and between the following Pins with the control unit connector pulled off (Connector is connected at hydraulic unit): Pins 5, 53, 54 and additionally 3, 4 and 6 on ABD vehicles to terminal 87.
Specification: approx. 9... 12 Ohm in each case.
PIN 25, 26,33 and additionally 34 on ABD vehicles to terminal 87. Specification: approx. 4. .7 Ohm in each case.
If specification is o.k., proceed with 7.
If specification is not o.k., locate fault. The fault may be located between the control unit connector and the wires up to the connector of the hydraulic unit or within the hydraulic unit.
To check the wires, pull off 15-pin connector from hydraulic unit (pull slide upwards). Check all solenoid wires between control unit connector and hydraulic unit connector according to wiring diagram for open circuit and short to positive or short to ground.
To check the hydraulic unit, measure internal resistance of solenoids.
PIN 7, 8,10 and additionally 1, 2 and 9 on ABD vehicles to PIN 15. Specification: approx. 9...10 Ohm in each case. PINS, 6,11 and additionally 13 on ABD vehicles to PIN 15. Specification approx. 4. .5 Ohm in each case.
Specification not o.k.: Replace hydraulic unit.
7. If all test steps are o.k., replace ABS and/or ABS/ABD control unit on a trial basis (final stage faulty).