Thread: The dreaded P420 code in CA

My 2007 Grand Prix has a recurring P420 engine light code, meaning a bad catalytic converter (or bad O2 sensor?). In CA, cats are replaced by dealers only for $1400. I cannot buy a new one for less than $1100 unless I travel out of state and bring one back. I have tried lacquer thinner in the gas, and fuel system additives, but the light keeps coming back on. Should I try a new O2 sensor? Defouler? Any other suggestions? The engine runs great. I replaced the spark plugs and wires, and have a new radiator with clean coolant.

Originally Posted by ericspecullaas

Ummm what???? Cats can be replaced by any exhaust shop yes ca cats do cost more but you dont have to go to the dealership to have them put a new one in.

I wish you were right. Exhaust shops cannot get after market cats; they come from dealers only--for $1100. The only savings would be in installation, if anything.

In CA, Magnaflow only sells cats through dealers (who charge $1100 just for the part), and Magnaflow has no cats for a 2007 Grand Prix. Thanks, though.
Exhaust shops, like Meinke, won't fix it because they can't get an after market cat for my car. It's frustrating. I need to register my car through my dad in Arizona, and get it fixed and smogged there.

ZZP downpipes look great, but they're not legal in CA. I found lots of 49-state legal cats, and I live in state # 50.
How do I check the O2 sensors -- with a multimeter and a propane torch (autozone.com)?

I thought of that; my Dad lives in Phoenix. I could also drive to Las Vegas in 4 hours and get a cat there. The problem would be a visual inspection of the cat when I get it smogged (yes, they look). I would have to "tip" them to look the other way, but I could register my car and legally drive it again.

I think I'll try to get the darn thing off and soak in soapy water first. Maybe that will fix it.

I have already gone through 2 after market cats ...600$ later still have 420 code...if i get the expensive one ,will it work?

No ive been dealing with this so long..i justwant to get it fixed the right way. im just worried its going to blow the new cat...its 1800$ but i dont wanna lose my baby...