Did you swap the '03 seat belt buckle onto the new '00 seat? That needs to be done, so that all components of the SRS are from the same model year? Also, if your '03 had side (seat) airbags, the replacement seat will need to have those '03 airbags installed into it. It is also possible that your '03 seat track had a seat position sensor, and the '00 seat track doesn't. Good luck.