Return-pump fault

The return pump is activated via the engine relay.

With this fault, the DSC indicator lamp, the ABS indicator lamp and the general brake warning light (red) are on.

All traction control functions are disabled and only the conventional brake remains available.

Possible cause(s) of fault:

• The voltage supply for the engine relay is interrupted (fuse, connector, cable)
  
• The ground connection is interrupted
  
• The engine relay is defective
  
• The return pump is defective
  

Storage condition(s):

• The return pump is activated briefly on moving off and monitored for faults.
  

Troubleshooting procedure:

• Check of the power supply of the engine relay (pin 2, terminal 30)
  
• Check of the ground connection (pin 1)
  
• Remove the control unit for traction control and supply current directly to the return pump via the two spring wiping contacts.
  Important!Use terminals suitable for high starting current (approx. 50 A)
  If the return pump starts up, the engine relay is defective and the control unit for traction control must be replaced.
  If the return pump does not start up, the return pump is defective and the hydraulic control unit must be replaced.
  

Note

• The engine relay is integrated in the control unit for traction control.
  
• Renewing the control unit, see Service functions