you can find trouble codes for a 91-94 sentra here:
http://www.se-r.net/engine/ecu_codes.html
i don't know if they are the same or not, but i suspect that they would be. i'm pretty sure 5 short and 5 long is normal, but after that i don't know the codes. maybe george (p10det) would know. he knows a lot about a lot, especially our engines.