1-2 and 2-3 Shift Solenoids

1-2 Shift Solenoid Circuit:

Transmission 2-3 Shift Solenoid Circuit.:

Purpose:
The 1-2 and 2-3 shift solenoid (also called A and B solenoids) are identical solenoid devices that control the movement of the 1-2 and 2-3 shift valves. The 3-4 shift valve is not directly controlled by a shift solenoid.

The solenoids are normally open exhaust valves that work in four combinations to shift the transmission into different gears.

The PCM controlled shift solenoids eliminate the need for throttle valve and governor pressures to control shift valve operation.

Operation:
The PCM energizes each solenoid by grounding it through an internal quad driver. This sends current through the coil winding and moves the internal plunger out of the exhaust position. When energized the solenoid redirects fluid to move a shift valve.

The manual valve can hydraulically override the shift solenoids. Only in D4 are the shift solenoids totally determining what gear the transmission is in. In the other manual valve positions, the transmission shifts hydraulically, shift solenoid state catches up when throttle position and vehicle speed fall into the correct ranges.

Location:
The 1-2 and 2-3 shift solenoids are attached to the valve body in the transmission.