What causes my 2004 chevy colorado check engine light to come on?

The reason why the check engine light might be coming on in the 2004Chevrolet Colorado could be from many different reasons. You won't really know why until You get the codes for the reason pulled and then You can find out. Some of the causes can be pretty minor like a worn, loose or missing gas cap or in between like an oxygens sensor issue or they can be more major like a problem with the catalytic converter. Sometimes You can drive for a while and the check engine light will go away by itself. You can also try to tighten the gas cap or get a new one if it is missing to see if that is the issue. If the problem is with the catalytic converter it would cost anywhere from $170 to $220 in labor costs.