Ok, well two weeks ago I replaced my entire exhaust from the headers back. I also ended up replacing the front O2 sensor, because I was getting a code for that after the install. Now for some reason, I randomly get an SES light, but when i use a scan tool on it, no codes come up. I press the clear button on my scan tool, and the light goes away. Anyone else ever have this happen?

 

Your scan tool can't pull all the codes that the Nissan Consult unit can. Try pulling the codes manually and see what you get.