In some cars and especially the newer cars of today if the brake fluid or other fluids are low then it can trigger the computer to tell the check engine light to come on if the brake fluid reservoir has a fluid sensor in it.
Another thing that could happen if your brake fluid is low is the brake light on your dash could come on or you'll have a softer brake pedal.
If your brake fluid is low then you might have a leak somewhere that needs fixed. You shouldn't be losing brake fluid normally.
Other things that could cause your check engine light to come on are low transmission fluid, low tire pressure, engine misfires, bad spark plugs, faulty ignition coil or coils etc.
And something as simple as a broken, loose or missing gas cap can trigger the check engine light to come on.