Automatic Transmission Fluid Pumps

Mechanical Automatic Transmission Fluid Pump 

The mechanical ATF  pump is an integral part of the transmission. The ATF  pump is used to supply hydraulic pressure for the operation of the control valves and clutches. The ATF  pump is also used to pass the ATF  through the transmission cooler and to lubricate the gears and shafts.

The mechanical ATF  pump is a double stroke, vane type pump and is located below the transmission input shaft. The pump is driven by a chain drive from a sprocket located on the input shaft.

Electric Automatic Transmission Fluid Pump 

A low voltage 12V electric ATF  pump is located in the transmission, at the rear of the Mechatronic valve block.

The electric ATF  pump is connected to the transmission hydraulic circuit and is controlled by the TCM  . The pump has 2 electrical connections with the TCM  :

• A Pulse Width Modulated (PWM) connection for electric motor operation.
• A diagnostic feedback and a ground.

The electric ATF  pump provides pressure and flow to the transmission and the engine disconnect clutch when the vehicle is stationary. The electric ATF  pump also provides pressure and flow and when driving in EV  mode and the CIMG  speed is slow.

The electric ATF  pump can have two failure states:

• The integral software in the electric ATF  pump can report back a permanent failure to the TCM  .
• The TCM  can detect the loss of 'pump status' signal.

In both cases the TCM  will send a request to run the CIMG  to the PCM  on the FlexRay bus. The request to run the CIMG  which will rotate the transmission input shaft and operate the mechanical ATF  pump.