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 vehicles 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.