Hydraulic Pump

The Hydraulic Pump, installed in the Hydraulic unit, generates the pressure required to operate the clutch and perform gear changes.

The pump is a piston pump driven by an electric motor, actuated by the SMG control unit via a relay so that oil pressure is always between 45 and 80 bar. Power consumption of the electric motor is 20 amps.

When the fluid pressure in the hydraulic unit drops below 45 bar, the SMG II control unit activates the relay and supplies the electric motor with B+. At a hydraulic pressure of 80 bar, the SMG II control unit deactivates the relay.

To ensure there is sufficient pressure when the engine is started, the hydraulic pump is activated below an accumulator pressure of 45 bar when the door is opened or the vehicle is unlocked with the key or the remote.

In the event of a hydraulic system failure the gearbox warning lamp is turned on in the IKE and if hydraulic pressure fails to build, no further gearshifts are allowed. This allows the reserve pressure in the accumulator to be used to place the gearbox in the Neutral position when the vehicle comes to a stop.