Check the oxygen sensor wire, i replace the o2 sensor and it came on still, it turn on to be one of the o2 sensor wire was loose, ever since then light never came on again.
the truth, the only thing that happen to my gs is the door actuator, its nothing major, only had to replace one of my door motor once, about 15 bucks for the parts. but everything else is great. Nothing has gone wrong, car has treated me well.