Why engine light came on?
What engine light? If you are referring to the check Engine Light, then the computer has detected a problem that effects the emissions controls.
When your car hit 150000 miles the check engine light came on is this coincidence or is the car programmed to have the engine maintenance at 150000 miles?
Your check engine light just came on and at the same time noticed your drl are off Is that the reason for the check engine light to be on?
Will a check engine light on a car stay on for awhile after a new engine is put in a car to replace an old one?
In most cases the check engine light will come on after you put a new engine in it, it can come on for various reasons, In my case my check engine light came on because my oxygen sensor was reading the fumes from my exhaust in which came from my last engine. eventually iit will turn off but its good to get a diagnostic to be sure that they wouldn't have to replace your sensor