I have a 2006 Cadillac XLR V, automatic trans, with 43000 miles that is throwing a P0430 OBDII code and turning on the check engine light. Occasionally (twice so far), the check engine light will turn off on its own after driving the car, but eventually comes back on. I am adding Techron to the fuel every fill up for a couple thousand miles now as an attempt to remedy. My dealer said it needs a new cat (estimate $2K). I heard you say the codes are not where you finish the diagnosis, but where you start. Is there anything else I can service before I decide the cat is the real issue? Can it be O2 sensor or something? (I knew the XLR would consume $$, my other cars are Toyota :))
See here for other possible causes, apart from the cat -
https://www.autocodes.com/p0430_cadillac.html
Cats, on their own, don’t fail. It’s other stuff that makes them fail. New cat will fail, too, if cause of failure is not remedied first! True, …
Anyway, … check oil consumption, check for exhaust leak upstream of cat, … all the way down to cat’s last flange. Check cat for physical damage: dents, cracks, distortion, noise if you shake it. Check that first. If that’s all OK, … go after engine: air filter, mass air flow, plugs, coils, … make sure these items are clean, gapped, working as should.
Anyway, … that’s where you start. Fix all that, … than, just perhaps, if you install a new expensive cat, you won’t ruin it! It’s that how it all works, …
F.S.
