Auxiliary Transmission Fluid Pump
WARNING: This page is about a different car, the 2012 GMC Yukon, 2012 Chevrolet Tahoe, and 2012 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
The auxiliary oil pump is driven by a 12V AC motor controlled by a dedicated auxiliary fluid pump control module that is mounted in the engine compartment. Control of the auxiliary fluid pump is managed by the hybrid powertrain control module, which communicates directly with the auxiliary fluid pump control module. The purpose of the auxiliary fluid pump is to supply oil to the transmission for lube, cooling and clutch application during Auto-stop when the engine is off and the main transmission pump is not operating. The auxiliary fluid pump is commanded on when propulsion is active, such as when the vehicle is in electric only or stopped at a traffic light.