I have a 1999 Toyota Sienna XLE. The transmission failed at 57,000 miles and was replaced under warranty. Now at 126,000 miles the check engine light has come on. The dealer says this is a PO770 error code and I need to replace the transmission for $3600. I am not having any problems at all with the transmission but I understand that the vehicle will not pass inspection as long as the check engine light remains on. Do I have to spend $3600 to replace a part that is working fine or is there some way to fix the problem at least until the transmission actually fails mechanically?