replacing TCM...2 times in one day...WHY? HELP PLEASE!

Ok...now what...replaced the TCM and everything worked great. Transmission shifted beautifully, cruise control worked again, speedometer and odometer without any problems....for about 10 minutes....then back to limp mode. Took it to have another scan run and got p0700...again. At first it was p0500, p0715, p0700. Also, already replaced input and output sensors on the transmission. Now scan is just showing p0700. We figured we got a bad used TCM so we traded it for another. Same thing. What could it be? The trans. shop said they checked all the wires and that everything looked fine. PLEASE HELP!!! What happens if the TCM you replace is not the EXACT same code as the one the vehicles VIN calls for? Is there a special way this tcm needs to be installed to reset the fault codes? Having a hard time trusting mechanice. AAMCO trans. specialist tried to tell me input and output sensors were "deep inside the transmission and that it would have to be taken apart to replace them" ..not true...very easy to replace. Do any of you know anyone I can call or any other sites I can look at for help?
Thanks a bunch!

ok..just unhooked TCM and disconnected battery for 10 min. and then replugged the TCM. Also did that ignition off on three times that I saw on another post. Code I got was a 12. Now I need to find out what that is. No change at all on anything. Also noticed no reverse lights. When the TCM did work (for 5 miles) the doors also locked when the van was put into reverse. Not doing that now. Check engine light not back on yet but still in limp mode. Maybe I didn't drive it long enough again for the check engine light to come back on. Dealer says TCM numbers must match exactly. They checked my VIN and my van calls for TCM that ends in AB or AC. Salvage yard and some mechanics I've spoken to say that the exact match doesn't matter and that the dealer doesn't know what they're talking about. TCM's we put in twice today end in AA, not AB or AC as dealer specified. How do I know who to believe? If the numbers didn't matter then why did they make ones with different numbers? Dealer said three different ones for 1997 3.3, I guess that's what the AA, AB, and AC are.
Any suggestions?

ok..just unhooked TCM and disconnected battery for 10 min. and then replugged the TCM. Also did that ignition off on three times that I saw on another post. Code I got was a 12. Now I need to find out what that is. No change at all on anything. Also noticed no reverse lights. When the TCM did work (for 5 miles) the doors also locked when the van was put into reverse. Not doing that now. Check engine light not back on yet but still in limp mode. Maybe I didn't drive it long enough again for the check engine light to come back on. Dealer says TCM numbers must match exactly. They checked my VIN and my van calls for TCM that ends in AB or AC. Salvage yard and some mechanics I've spoken to say that the exact match doesn't matter and that the dealer doesn't know what they're talking about. TCM's we put in twice today end in AA, not AB or AC as dealer specified. How do I know who to believe? If the numbers didn't matter then why did they make ones with different numbers? Dealer said three different ones for 1997 3.3, I guess that's what the AA, AB, and AC are.
Any suggestions?

I would try to find a TCM with the AB or AC at the end of numbers and see if that works, also I seem to remember that after replacing a TCM the TCM needs to be flashed by the dealer ( I could be wrong about that but check with dealer).

Code 12 means that the battery has been disconnected in the last 50 cycles, nothing to worry about.

ok...now the a/c is not working. Quit this morning. Is this just a fluke? Going to pick up a module with AB on the end today. Praying it works!!!

Code 12 is battery disconnected during last 50 starts.