Problem With Car, Engine Warning Light On

[DRIFTPIG]

Hey guys, i went to start my pig the other day and the damn battery was flat. I didn't leave anything on and i hadn't started it for 2 weeks, but i have left it for a week or so without starting on other occasions.

Anyways, i have one of those battery chargers/engine starters so i connected it all up properly to the fuse box jumper part under bonnet, charged it for 10 mins then set it to start and away she went. No problems at all! Took her for a spin for bout 5 mins and the whole time the orange engine warning light was on. It flickered and flashed every now and then when i gave it a bit but mainly just stayed on. I have checked as many wires as i can find which all seem good. i drove home, turned the car off, then re-started it and it kicked over no problems?

Any ideas? Should i not drive it or what? its running a power fc too if that makes any difference! lol