The "sensor" light is a maintenance reminder used on 80's Nissan vehicles. It comes on every 30000 miles and is reset by pressing a button in on a module usually located behind either the left or right kickpanel.

 

I don't understand why it would have came on, though; if it comes on every 30k then why would it come on at 158k?

 

They don't always go off exactly at 30,000 mile intervals. Nissan actually says in the service manual to reset the lamp using the button on the "hold relay" until you get to 90,000 miles and then reset it so the lamp does not come on again by disconnecting the warning lamp electrical connector. At least that's the way it is for the B11 Sentras, which have the "hold relay" behind the passenger side kickpanel. If you give me your year and model, I can provide you with more specific info for your vehicle.

 

89 sentra sport, i think? it came stock with side skirts and a wing; i haven't seen one like it at all, so idk.
But lately, it still comes on, but only when im in second gear going up a hill; i think its like an O2 sensor or something, if they have them. I need to scan the ECU codes to get more specific, though.

 

www.troublecodes.net/Nissan

 

My EGR valve, I think it was called, is dirty or just not working and it's saying on because my speedo doesnt work which is getting fixed tomorrow!