Test 24/Fault Code 40
Test point 24Return pump Open circuit / short to ground / short to positive
Fault code 40
Feedback (Return pump monitor) to control unit is missing.
Using System Tester 9288, the Drive links menu can be used to check operation of the return pump.
Select Drive links menu and select the pump relay on this menu (Specification: Return pump operative).
1. Pull off return pump relay (R65INO.1). To allow the relay cover to be removed, detach the relay holder (press out body-bound rivet No.3). Check connectors for correct engagement in relay base (connector may have partially slipped down out of base). Check if system voltage is present at terminal 30 of relay base (approx. 12 volts). Check fuse and wiring if required.
2. Jumper terminals 30 and 87 on relay base. Return pump should run now. If the return pump does not run: Check attachment of ground cable at return pump (on return pump and battery ground) (Contact resistance due to poor screw-on connection). Check wiring of make circuit from relay base to hydraulic unit according to wiring diagram. Replace hydraulic unit if required. Prior to this, check if return pump is actually faulty (Use a separate wire to apply system voltage to PIN 3).
3. Fit return pump relay to relay base. To make sure that the connectors are not damaged in the relay base and that they are not pushed down, push the relay carefully into place (do not tilt relay). Check again with System Tester (as described above) to make sure the return pump is running. If pump does not run: Replace relay on a trial basis and repeat procedure.
4. Pull off control unit connector. This requires the control unit to be removed. Check control circuit according to wiring diagram.
5. Check wiring for pump motor monitor on control unit connector) (Control unit connector PIN 19).