B350 1 Ton Van V6-239 3.9L (1990)
Torque Converter Clutch Solenoid: Description and Operation
Transmission Electrical Connections (3 Speed, With Lock-up)
On vehicles equipped with an A-999 transmission (Non-California only), the engine controller controls the locking up of the torque converter through the
lock-up solenoid. The engine controller controls this solenoid by applying and removing the ground from its circuit.