What does the check engine light on a 2003 Camry mean?

When the check engine light comes on in the 2003 Toyota Camry it can mean any amount of things. It can be something really minor like a loose, broken or missing gas cap or maybe something wrong with the oxygen sensor. It can also be something more serious like an engine mIS Fire which causes a problem with the catalytic converter. To check if it is a problem with the gas cap You can drive around for a bit to see if the problem goes away or You can try to tighten the gas cap. If it is a problem with the oxygen sensor, a new one costs between $30 to $70. If You need to reset the check engine light You can unplug the battery and wait for about 20 minutes or so and plug it back in.