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.