Mercedes Benz S 550 4MATIC Technical Problem #LI46-30_P-054912 Date: 121029
Steering - Electrohydraulic Power Steering Pump Leak
Oil leak at power supply connector of electrohydraulic power steering pump (EHPS), sometimes with reduced power assistance
Topic number LI46.30-P-054912
Version 1
Design group 46.30 Power steering pump
Date 10-29-2012
Validity MODEL 221 as of ident number #A 286000 up to ident number #A 495000 except vehicles with code 489 (Active Body Control)
MODEL 216 as of ident number #A 023500 up to ident number #A 030800 except vehicles with code 489 (Active Body Control)
Reason for change
Complaint:
In individual cases oil may be seen at the power supply connector of the electrohydraulic power steering pump (EH-PS) A91/1 (see attachment 001)
and at the wiring harness for the power supply (see attachment 002), sometimes in combination with noises when steering and/or with reduced power
assistance.
The capillary effect may have cause the oil to penetrate as far as the front prefuse box F32/3 (see attachment 002) or to ground connection W2 (see
attachment 002).
There is no fault code stored in the control unit of the electrohydraulic power steering pump.
Attachments
Cause:
Internal leakage of electrohydraulic power steering pump (EHPS).
Remedy:
1. Replace electrohydraulic power steering pump.
2. Replace power supply wiring harness, routing and fastening the new wiring harness parallel to the existing wiring harness. Cut off the power
2010 Mercedes Benz S 550 4MATIC (221.186) V8-5.5L (273.968) Page 8
supply connector and the ground connection of the old wiring harness at a suitable point and tie them back so that the line does not touch
anywhere.
3. The front prefuse box F32/3 must also be replaced if oil is seen to have penetrated this far (see attachment 002).
Symptoms
Parts
WIS-References
2010 Mercedes Benz S 550 4MATIC (221.186) V8-5.5L (273.968) Page 9
2010 Mercedes Benz S 550 4MATIC (221.186) V8-5.5L (273.968) Page 10
Attachment
Steering - Electrohydraulic Power Steering Pump Leak
Oil leak at power supply connector of electrohydraulic power steering pump (EHPS), sometimes with reduced power assistance
Topic number LI46.30-P-054912
Version 1
Design group 46.30 Power steering pump
Date 10-29-2012
Validity MODEL 221 as of ident number #A 286000 up to ident number #A 495000 except vehicles with code 489 (Active Body Control)
MODEL 216 as of ident number #A 023500 up to ident number #A 030800 except vehicles with code 489 (Active Body Control)
Reason for change
Complaint:
In individual cases oil may be seen at the power supply connector of the electrohydraulic power steering pump (EH-PS) A91/1 (see attachment 001)
and at the wiring harness for the power supply (see attachment 002), sometimes in combination with noises when steering and/or with reduced power
assistance.
The capillary effect may have cause the oil to penetrate as far as the front prefuse box F32/3 (see attachment 002) or to ground connection W2 (see
attachment 002).
There is no fault code stored in the control unit of the electrohydraulic power steering pump.
Attachments
Cause:
Internal leakage of electrohydraulic power steering pump (EHPS).
Remedy:
1. Replace electrohydraulic power steering pump.
2. Replace power supply wiring harness, routing and fastening the new wiring harness parallel to the existing wiring harness. Cut off the power
2010 Mercedes Benz S 550 4MATIC (221.186) V8-5.5L (273.968) Page 8
supply connector and the ground connection of the old wiring harness at a suitable point and tie them back so that the line does not touch
anywhere.
3. The front prefuse box F32/3 must also be replaced if oil is seen to have penetrated this far (see attachment 002).
Symptoms
Parts
WIS-References
2010 Mercedes Benz S 550 4MATIC (221.186) V8-5.5L (273.968) Page 9
2010 Mercedes Benz S 550 4MATIC (221.186) V8-5.5L (273.968) Page 10
Attachment
