Shift Solenoid: Description and Operation

The shift solenoid valves are two identical, normally open, electronic exhaust valves that control upshifts and downshifts in all forward gear ranges. These shift solenoid valves work together in a combination of On and Off sequences in order to control the positions of the 1-2, 2-3, and 3-4 shift valve trains. The PCM monitors numerous inputs in order to determine the appropriate solenoid state combination and the transmission gear for the vehicle operating conditions.

The PCM energizes the shift solenoids by providing a ground to the solenoid's electrical circuit. This sends a current through the coil winding of the solenoid, thereby creating a magnetic field. The magnetic field repels the plunger inside the solenoid. This seats the solenoid metering all against the fluid inlet port. This action prevents the exhaust of fluid through the solenoid and provides an increase in fluid pressure at the end of the shift valves. This fluid pressure initiates an upshift by moving the shift valves.

Shift solenoid resistance should measure between 19-24 ohms when measured at 20°C (68°F) and between 24-31 ohms when measured at 33°C (190°F).

The shift solenoid valves should energize when the volt is greater than 7.5 volts. The shift solenoid valve should de-energize when the voltage is less than one volt.