Hi Steve. Welcome to the forum. Getting stuck in second gear is "limp-in" mode that lets you drive it slowly to the repair shop without needing a tow truck. The Check Engine light should be on too, and the stored diagnostic code will just say there is at least one code stored in the transmission computer. You must cycle the ignition switch off and back on to get it out of limp-in mode, as you've found out.
Defective sensors can cause a default to limp-in, but with high-mileage vehicles it is more common to have clutch plate wear and slippage. That slippage is what sends it into limp-in mode. On older transmissions, when the clutch plates wore, the shifts gradually got sloppy and some slippage occurred. In these computer-controlled transmissions the computer watches how many ccs of fluid it takes to apply each clutch, and it constantly updates the overlap between applying the next gear before releasing the previous one. That's how it maintains the nice crisp shift feel, ... Until the day comes when it can't update any more. That's when the slippage is detected.
An experienced transmission specialist will connect a scanner to access the computer and read the "clutch volume index". That is a set of four numbers corresponding to the volume of fluid it takes to apply each clutch. From those he can tell how worn the clutch plates are. Stored fault codes will indicate other circuits or systems with a problem.
Saturday, November 13th, 2010 AT 2:35 AM