Rear ending shouldn't affect it but you will never know until the cause is found.
The fault codes will be in the Transmission Computer (EATX). The Check Engine light is for the Engine Computer (PCM). Many aftermarket scanners won't access the Transmission Computer. To reset the computer from limp-in, all you have to do is turn the ignition switch off and restart the engine.
Disconnecting the battery will cause two problems. First, that will erase all of the diagnostic fault codes that are currently in memory. Those are the single biggest clues to the cause of the problem. When they are erased all of that valuable information is lost. Now you'll have to drive the car again until the problem acts up and hope all of the pertinent codes set again.
The second problem is the computer knows how much fluid it takes to apply each of the four clutch packs. That changes as the clutch plates wear. Unlike older transmissions that gradually developed sloppy shifts over a period of more than 100,000 miles, your computer compensates for that wear. It continually updates the timing of how it engages one gear before it releases the previous one. That results in a nice crisp shift that covers up any clutch wear until the day comes when it can't update anymore. That's when the slippage occurs. When the computer detects that slippage, it sends it to limp-in.
All of that updated shift schedule information remains in the Transmission Computer's memory. When the battery is disconnected, as when replacing it, that information is lost. The next time you drive the car, it starts out with the values programmed in at the factory. Typically it takes about a dozen shift cycles from first gear to overdrive, and a good two to five miles to relearn the characteristics of any clutch pack wear. Until that happens, it could shift real sloppy or it could shift real hard like a race car. Now you have two problems. The computer is requesting clutch engagement at the wrong times coupled with whatever is causing it to go to limp-in. The combination can result in the wrong fault codes being set.
The solution now is to have the fault codes erased with a scanner that can access the transmission computer. That should be done after the car is driven long enough to update the shift schedules. Erasing those codes won't affect the rest of the updated memory. Next, drive the car again until it goes to limp-in. Then you can have the codes read again and they should be accurate.
Sunday, February 6th, 2011 AT 3:59 AM