1-2 & 2-3 Shift Solenoid Valves

WARNING: This page is about a different car, the 2002 Buick Regal, 2002 Buick Century, 2001 Buick Regal, and 2001 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

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 to control the positions of the 1-2, 2-3 and 3-4 shift valve trains. The PCM monitors numerous inputs to determine the appropriate solenoid state combination and the transaxle gear for the vehicle operating conditions.

SHIFT SOLENOID OPERATION

Gear Range		Solenoid Position
"D" (Drive)
1st Gear		1-2 ON/2-3 ON
2nd Gear		1-2 OFF/2-3 ON
3rd Gear		1-2 OFF/2-3 OFF
Overdrive		1-2 ON/2-3 OFF
"3" (3rd)
3rd Gear		1-2 OFF/2-3 OFF
2nd Gear		1-2 OFF/2-3 ON
1st Gear		1-2 ON/2-3 ON
"2" (2nd)
2nd Gear		1-2 OFF/2-3 ON
1st Gear		1-2 ON/2-3 ON
"1" (Low)
1st Gear		1-2 ON/2-3 ON
"R" (Reverse)		1-2 ON/2-3 ON
"N" Or "P" (Neutral Or Park)		1-2 ON/2-3 ON

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 ball 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 68°F (20°C) and between 24-31 ohms when measured at 190°F (88°C).

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