I have a 91 eclipse AT non T, and my tranny is stuck in only one gear, i think 3rd. My question is where is the tcu? Behind radio is one box mounted with 3 screws that i replaced when I got the car to make it run better (the ECU). There is no other box behind there. That box has 3 plugs going into it. Is the TCU built into the ECU? if not where could I find it?