You might try manually checking the error code on your ECU, you can go to this link and it shows you how to do it.
http://www.nissanforums.com/showthread.php?t=84062
I also had a similar problem with my 92 sentra. Whenever I accelerated (especially at night), the check engine light would come on periodically. Actually, it was like it would randomly come on while driving, maybe even when I hit the brakes, but once I hit the accelerator, it would turn off. Almost like it switched around, and I could always get it to turn off by usually hitting the brakes and then the gas. I replaced my O2 sensor and I havent seen the light since. I would personally check the code first though...