Nissan Repair: Locating TCM, nissan silvia, diagnostics test

Question
An automatic transmission mechanic has had my car (93 Nissan Silvia) for a week attempting to fix an issue that was causing my silvia to rev to about 5K before changing gears. At the end of day one he explained that a solenoid had to be replaced. Such was done. By day 3 he explained that he needed to obtain a wiring map because some message wasn't being relayed correctly. I managed to obtain this however now after day 5 I've been told that he needs a TCM diagram before I can have my car back. Truthfully I am a girl and I have no idea what he is talking about but I have exhausted all avenues trying to get my car fixed just so I can have it back. Is there any chance you could inform me where the transmission computer is located. I've been told to try under the seats and inside the kick panels but this unfortunately has not been correct. The mechanic has also looked inside the drivers door. I just really want me car back before he pulls it to bits. Surely a week to replace a solenoid is stretching reality? Please say you know where the item can be found on the car. Thank you in advance for any help you can give.

Answer
Peta,

Get them to give you your car back and go to Cottman Transmissions.  They will run a diagnostics test on the transmission and replace the solenoid or governor.  There is a remote chance that you will need a new TCM as it is the computer that shifts the transmission.  But, that is a long shot.  The computer for the transmission is really close to the transmission as it connects to the solenoids inside.  So, it is not in a door or under the seat.  Since yours is so old the main ECM runs the show and the small board that runs the transmission should not be the problem.  Since yours is a Silvia (240SX here in the US) it might be a good idea to get the dealer to do the diagnostics if you do not have a Cottman Transmission shop.  But, in either case get someone that has a Consult Scan tool that can talk to your car.