I took my car in to the shop because the "check engine" light was on and found out this was simply due to my gas cap being loose. Why would that set off the warning light? – Louis in Duncan, B.C ...

You fixed your car's issue, but the dash is still lit up like it's Christmas. Here's how to reset the check engine light in a few simple steps.

It is entirely possible that the battery was faulty causing low voltage at the computer, which in turn can turn on the check-engine light.