When the Transmission Computer detects a problem, it goes to "limp-in" mode where it stays in second gear. That is designed to let you drive it slowly to the repair shop without needing a tow truck.
As a general rule, if it starts out in first gear like normal, then upshifts to higher gears, then suddenly goes back to second gear, internal slippage of the clutch packs is the most likely cause. That requires the transmission to be rebuilt or replaced.
If you find it starts out in second gear right away, (it will have lower than normal power when leaving a stop sign, and you won't feel any shifts), it is more likely to be caused by a sensor problem. Those are relatively inexpensive repairs. You'll need to find a mechanic with a scanner that can access the Transmission Computer to read the stored diagnostic fault codes. The code(s) will lead to the circuit or system with the problem, not necessarily the defective part.
Wednesday, January 19th, 2011 AT 3:48 PM