I started my car at 8pm on mon and the service light engine came on. I have no mods, no nothing. At morning it was fine, but then at night i don't know what happened it just turned on(it doesn't blink)

 

The dealer tells me that there's a problem on some maximas with the ecu registering a catalytic converter malfuction when in fact it's perfectly fine. I'd say go take it to the dealer. I had the same problem and they replaced the cat converter since it was before they figured out the ecu problem. Regardless, it should be covered under warranty.

good luck