check engine light

I have a 2002 Crown Victoria LX, that sat for a week with the dome light on and extremely low on gas. When I started it, about 3 miles down the road the "check engine" light came on. The car has 43, 000 miles, and it seems unlikely that it would be an o2 sensor at this point. The battery was still strong when I started it.

Any secrets before I go to the codes?.... Tks.

Welcome to the forum. Check if your gas cap is tight.

After gas cap check, have the codes read and post exact numbers back here and we can help.