What would cause my 2003 Chevy Tahoe check engine light to come on?

When the check engine light comes on in the 2003 Chevrolet Tahoe it means that there might be something affecting the vehicle's emissions control system. It could mean many different things from something simple like a loose or missing gas cap or something major like a problem with the catalytic converter or something in between like a problem with the o2 sensor. To have the check engine light go away You can either drive for a while and hope it goes away by itself, You can disconnect the battery for about 10 minutes and that might reset it or You can run a scanner and find and fix the problem. If the problem is the gas cap, just try to tighten it or see if it is missing. If the problem is with the catalytic converter, a new one costs between $120 and $150 in labor costs and about $1,610 to $1,620 in parts costs.