Well, any cheapo OBDII scanner would work to give you an error code that you could look up details and troubleshooting for easily online. I don't know if it would be more useful to you, but it certainly might be and it's also just darn cool: get a OBDII to bluetooth adapter? You can connect it to your phone or pc and just use a program from there to interact with it (Android, at least, has one called Torque that shows you pretty much every sensor and code that the car can output). I just got one, haven't gotten it in the mail yet but I've been looking up all kinds of stuff. Just look up OBDII to bluetooth and you'll find a bunch for like $5 or $10.
Beyond this, I suppose you could buy one of Toyota, or Nissan's dealership mechanic computers to also change some programmable settings in the car, but those things are naturally thousands of dollars...wouldn't recommend it.
