I have a 2000 Impala with a 3.8 eng. I took it for inspection and failed. Its has a code reading, P0420. I had the cat replaced about 2 years ago with a new rear 02 sensor. Ever since I replaced the Cat Ive had problems with the inspection passing but after a few tries it would finally go thru. Until now. Could the Cat have gone bad so soon? How do I check to see if both sensors are good. Also I recently replaced the EGR valve and cleaned out all the ports thru the system. Removed and cleaned the Throttle body and replaced everything with new gaskets. The car has always run great except for this P0420 issue. The car does have 184,000 plus miles on it, but runs great. Also where is the front 02 sensor located in case I have to replace it? Ive searched the forum, but I couldn't find any answers. Any help would be very much appreciated..
P0420 is the rear O2 sensor, like IffyG said, its aftermarket cats usually set off this code. If you have someone local with a tuner, they can delete this code from the PCM and you will never see it again (not a scanner and clearing the code, actually deleting the code form the PCM so it never looks for it again)
I had the same problem on a 2002 Camaro with the 3.8L. Aftermarket cat's don't work well on the 3.8L motors. Aftermarket Cat = Problems, Problems, Problems.
I never could get the car to pass our regular state I/M test.
I had to go into the state health department and have them do the old style tail pipe test in order for it to pass. It was a PITA!
Just buy a stock cat and be done with it. It will save you a lot of headaches IMO.
Thanks guys for your responses. Yes it was and after market Cat. I know it a good Cat, its just the incapability of the o2 sensor and the Cat that I think is setting off the code. After some more research, I was thinking of putting in an o2 simulator. After speaking to the local street rodders , they say it the only sure ticket to this dilemma. They say it solves the problem 100% of the time to pass emissions. Any thoughts on the o2 simulators? This one is from 3800 Performance.......
O2 sims ARE illegal and you will fail inspection if they see it.
PCM tunes are undetectable with a scanner and the inspection equipment. Plus, you get the added benefits of a tuned PCM. Better shift points, better fuel curves, option to have the fans run longer, option to run a lower temp t-stat, etc.
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