Expert: Roland Finston - 1/17/2012

Question
Transmission works in reverse and first gear. I you get up to 40 mph in 1st turn the key off and back on, It appears to go in to neutral and after slowing down drops back in to 1st.  Recently changed fluid and filter. This cured earlier problems. Then this started. Replaced solenoid pack, input and output speed sensors with no change. There is no noise coming from the Transmission and it has never slipped. Where is the TCM located and do you think this might fix the problem?
Thank you,  Robert Smith

Answer
Hi Robert,
I doubt it is the TCM. The best thing to do is get a fault code readout from the TCM memory using the diagnotic data link connector plug under the dash on the left side (or perhaps behind a small door on that same left side). It is blue in color and has 6 contact pins. You will be seeking a 2-digit number. Be sure to access the plug in the cabin, not in the engine compartment(that black plug is for the engine computer, not the transmission's.
The TCM in '94 I am not certain as to location but the '93 and '95 shows it on the back panel (firewall) just to the right of center. But the fault code number is what we will need to know.
The vehicle is of the OBD-I vintage and so needs that type of reader which many shops will have. Free code readout are available at some nationwide parts stores, like Autozone, but I am not certain if they have the OBD-I type. Let me know what trouble codes you get and we'll go from there.  Check to see if fuse 15 in the box in the engine compartment is good. It would be a 15 amp fuse if it is like the '95 model.
Roland