2001 Maxima 20th Aniv ed

No way to know without reading the codes (Autozone does it for free except in CA)

There are literally hundred of reasons that light can come on. You could need anything from a reset of the light to a new engine. Take it somewhere (AutoZone will do it for free) and get the problem code read out, then somebody might be able to help.

MIne started that after 50,000 miles of regular gas. I changed back to premium, the light went out and it has never come back on.

Believe it or not.

Coincidence

The use of lower octane fuel will cause pre-ignition, and the knock sensor will detect that. The computer will retard the ignition to the point that knock will be reduced.

My 97 Maxima requires not less than 93 octane fuel.

I'll bet that your car requires high octane fuel.

With high octane you get less pre-ignition, less knocking, no knock sensor signals being sent to the computer, less ignition retarding, and no engine condition light.

With higher octane fuel the computer may have advanced the ignition appropriately due to no pre-ignition, and that should give you more power and mileage. The higher octane fuel itself provides no added power or mileage, and it is not of higher quality. It merely burns slower to limit pre-ignition in high compression engines.

Ralph Hertle