WHAT CAN IT MEAN WHEN THE CHECK ENGINE SIGN IS ON A QX4 W/122k MILES?

It could mean many things. From emissions system faults, oil pressure, far too many to list. Have your OBD codes read at an auto parts store and do not pay them to do it. Write them down and come back here. Are you having any trouble with the car?

Start by checking that your gas cap is on properly, that is one of the most common things that will light up the CEL, and check your oil ......Then go to: https://owners.infinitiusa.com/iowners/.../manualsandguides/.../2000.pdf for a free owners manual if you don't have one

my 2001 infinity qx4 have the check engine light on and I when to auto zone the code that show is 0100 they told me is a mass airflow sensor but he told me to do a fuel injection cleaner and now my car is worst . it backfire will driving it and it go back and fort when is doing that I don't know what to do.

my 98 qx4 was doing the same thing run for a moment as long as it was sitting and you could not drive it not where and I put a distributor in it and it now drives fine it could be what is wrong why yours will start but has no power to go anywhere or over 10 miles per hour.

1998 infinity qx4 engine light doesn't turned on when you start the car