The Sentra ECU's that are housed in the black box are not just ECUs, but
PCM's (powertrain control module). In other words, they are both an engine and transmission
control module in one.
Later models they reverted back to the two seperate control modules.
Anywho, there are varying symptoms of this, from trouble codes stuck, oxygen sensor heater
problems, idling problems, misfires, no injector signals, no AC clutch activation, and no start to
name a few.
So to make a long story short, b15chik is right. Unfortunately, most cases the problems that arise are
misleading and usually the tech only has the option of trying a known good PCM to see if the problems