Shift Solenoid Valves: 1-2 and 2-3

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Shift Solenoid Valves

Courtesy of GENERAL MOTORS CORP.

The shift solenoid valves are two identical, electronic exhaust valves that control upshifts and downshifts in all forward gear ranges. These valves are normally open. 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 TCM monitors numerous inputs to determine the appropriate solenoid state combination and transmission gear for the vehicle operating conditions.

Gear	Solenoid 1-2	Solenoid 2-3
PARK, REVERSE, NEUTRAL*	ON	OFF
FIRST	ON	OFF
SECOND	OFF	OFF
THIRD	OFF	ON
FOURTH	ON	ON

IMPORTANT: The solenoid states are normally ON (1-2) and OFF (2-3) in the P, R, and N gears. However, these may change based on the vehicle speed and the throttle position.

The TCM energizes the shift solenoid valves by providing a ground to the solenoid's electrical circuit. This sends 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. It then provides an increase in fluid pressure at the end of the shift valves. This fluid pressure initiates an upshift by moving the shift valves. Refer to the oil flow diagrams for a complete description of the hydraulic control of the shift valves for each gear range.

The resistance on the shift solenoid valves should measure between 19-24 ohms when measured at 20°C (68°F) and between 24-31 ohms when measured at 88°C (190°F).

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.