.................................Need some more info. The light comes on for a multitude of reasons. Was the bike 3 quarts low???? If it's over full this will cause problems. How does it run? It's like a fuel injected car, any one of the sensors will cause the light to come on. If you have Tuneecu ( if not google it ) you can hook it up with a cable and check error codes or I've even used a Scantron to check the codes and google the code to find out what's wrong.
Do not overfill the oil. You need to find out the error code triggering the engine light.Would not run it with 3 extra quarts of oil in it(unless it did indeed need them). Like Linkdog said it will cause a whole bunch of other issues. Will have to get your bike scanned to know what your issue(s) are.
If it idles like crap and stumbles have a look at your MAP sensor hoses. They're under the tank but a little obscure. Try Googling MAP sensor hoses Triumph Thunderbird 1600 and you will find some photos and information. There is a forced adaptation ( 12 min. tune ) that you can do, when cold start the bike no throttle and let it idle till the fan turns on ( 15 - 20 min. ) let it idle for an additional 12 min. then shut it down. After every thing shuts down you are done, at no point DO NOT TOUCH THE THROTTLE. If it is a minor problem the light will clear once the problem is resolved after a number of cycles, exact amount I forget. The bike only requires 4.1 liters or roughly 4.5 quarts, the fact that it needed 3 quarts worries me..................................
Thank you, yes it was very low on the oil. and as for how it runs, Yesterday I went for a ride-Filled the tank, and when I was riding down the street it staled when I came to a light, So I rode it home and not continued my ride, that's when I check the oil....but the light is still on. I have started and let it idle for 15 minute multiple times....Light is still on I have not rode the bike since yesterday..I should take it for a test ride...Just don't want to screw the bike up if it means something bad.
On last Sunday went for a nice long ride...it ran great and came home no problems...Yesterday it sputtered so I added oil today and engine light is still on after multiple turn on's and off's.