The shift solenoid is located inside the oil valve connected to the valve body. The shift solenoid controls gear engagement and gear shift. The engine control module or the transmission control module in the vehicle's engine controls the shift solenoid electronically.
The solenoid valve opens when electrical signals are sent to appropriate shift solenoid. The opening allows transmission fluid to flow to the bands and clutch of the selected gear. The pressurized fluid enables the bands and clutches to engage the gear. Common symptoms of a faulty shift solenoid include delayed shifts, no downshifts or uncontrollable downshifts, and erratic shifts.