Transmission Fluid Pump - Auxiliary
The transmission fluid pump - auxiliary is a hydraulic pump driven by an electric motor. The transmission fluid pump - auxiliary attaches to the transmission case assembly. The transmission fluid pump relay - auxiliary receives voltage through the battery positive voltage circuit. The hybrid powertrain control module controls the auxiliary pump by providing the ground path on the transmission pump relay - auxiliary coil control circuit. When the control circuit is grounded, battery positive voltage is directed to the transmission fluid pump - auxiliary. Under certain conditions, the hybrid vehicle's engine will shut off and the transmission fluid pump - auxiliary will start running to keep the transmission hydraulic circuits pressurized and ready for the engine restart. This engine off condition is a fuel economy feature.