why would my check engine light be on if things were changed and reset .

on 1999 Dodge Stratus

I changed the air filter , the spark plugs in wires, also the O2 sensor and gas cap. what else can be keeping my check engine light on.

2 answers
Lots of differant things...save yourself further frustration and get it diagnosed.
agree with #1.it could be circuit issues and not sensor malfunction