Important: The shift solenoid resistance should measure 20-40 ohms minimum when measured at 20°C (68°F). The shift solenoid current flow should not exceed 0.75 amps. The shift solenoid should energize at a voltage of 7.5 volts or more (measured across the terminals). The shift solenoid should de-energize when the voltage is one volt or less.

The 1-2 and 2-3 shift solenoids (also called A and B solenoids) are identical 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 normally are open exhaust valves that work in four combinations to shift the transmission into different gears.

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

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

The pressure control solenoid takes the place of the throttle valve that was used on the past model transmissions.

Important: The manual valve hydraulically can override the shift solenoids. Only in D4 are the shift solenoid states totally determining what gear the transmission is in. In the other manual valve positions, the transmission shifts hydraulically and the shift solenoid states "catch up" when the throttle position and the vehicle speed fall into the correct ranges. Diagnostic trouble codes 081 and 082 indicate shift solenoid circuit voltage faults.