Circuit/System Description

The automatic transmission auxiliary fluid accumulator is used to provide transmission fluid line pressure to the transmission during an autostart event. The accumulator is externally mounted to the transmission case assembly. The engine control module (ECM) controls the automatic transmission auxiliary fluid accumulator solenoid valve by providing a ground path to the solenoid valve control circuit.

When the engine is shut off during an autostop event, there is no transmission line pressure. During an autostart event, the ECM commands the automatic transmission auxiliary fluid accumulator solenoid valve on, allowing transmission fluid to discharge from the accumulator, supplying line pressure to the transmission. The accumulator will start to recharge when the transmission fluid pump increases line pressure higher than accumulator pressure. Transmission fluid will flow through the solenoid valve until the ECM turns the solenoid off and also flow through a check valve.

The TCM monitors clutch slip during an autostart event. The DTC will set if the TCM detects that the accumulator system is not capable of supplying adequate pressure during autostart.