Nissan Repair: check engine light, nissan sentra gxe, nissan sentra

Question
Hello,
  I have a 1996 Nissan sentra GXE that has had a history of having the check engine light come on since 2001. The last 4 times the light was on was due to a faulty oxygen sensor. Last month I noticed the light started to come on again after having it serviced just 9 months ago for that problem. I disconnected the battery in hopes of having the light go out, and having the computer loose the stored code so the light wont come back on. Unless its a major problem in the emissions it has always worked for me. Well all was fine until last week when I had to get an emissions check done on my nissan, the car failed the test. It appears the check engine light would not come on at all; even before starting the vehicle, causing me to fail my emissions and not being able to renew my plates. I checked the bulb and fuse, and they were both fine. I tried to examine the fuse block for loose or disconnected wiring but could not find any. After attaching the fuse block back to the car I turned the engine over only to find that now the light is on, and stays on. I imagine that I have a short but there is one more thing I can't figure out. The engine light still does not come on when attempting to start the car. It only comes on now once the car is running. My question is what would cause a short in the wiring at the fuse block and why doesnt the light come on at all when attempting to start the engine when it's evident the light does work now?
                           Thanks, Mike

Answer
Mike,

The light circuit works and the computer is at fault.  I would disconnect the battery and then disconnect the computer and wait about ten minutes to reconnect it.  Then reconnect the battery.  If this does not work then get a computer from a wrecking yard and replace it.  Email me back if you have problems.