GM Service Manual Online
For 1990-2009 cars only

Third and Fourth Gears Only

Checks

Causes

2-3 Shift Solenoid Valve(305)

    â€¢ Stuck ON
    â€¢ Solenoid is plugged
    â€¢ Electrical malfunction

1-2 and 2-3 Shift Valves

Both are stuck in an upshifted position