P0420

2002 Chevy Malibu LS 3.1L v6
Catalytic Converter clogged up, and lost power, no codes :screwy:???. I replaced the converter, the car ran like new again. After about 4 months I recieved a P0420 code. I have now replaced both O2 sensors and the code still comes back. Could an after market converter cause this?

I got the same code today on a 98.
There some tricks but the best way might be to
fill up with the best gas you can get, 2 tanks should be good enough.

Cheers
Stripe

Yes an aftermarket cat can cause this, do a site search for that code there are good articles there, 2 tanks of any type gas will not permanantly correct that code.

I have this same problem on my 2002 Malibu and it's nerve racking!
My original cat plugged on the interstate and was replaced with what the mechanic said was a official GM part. Ok, so no problems for a year and a half.

In the mean time I've had my head, intake, and valve cover gaskets replaced because of a steady coolant leak. A tech had pinched the valve cover gasket and oil leaked on to the exhaust manifold behind the engine for a few weeks. So then that was fixed and no more leak.

Late last year the P0420 code came. I have since moved states and took it to another garage. The tech there said the cat was aftermarket, failed, and needed replaced. So he replaced that cat and it wasn't a month later the code came back. He again replaced the cat because he thought something had failed in it.

6 months later the code is back and he can't figure out why. He said the O2 sensors are working properly and as far as I can tell the car runs fine. The only thing I notice is I believe the gas mileage has dropped off a bit and the blasted red light is here to stay.

I live in a state with emissions inspections and he said not to worry about the code and he'll pass it anyway.

Anyone have any ideas about this code and the Malibu?

Two nights ago I added 3/4 of a pint of Sea Foam to a full gas tank and the remaining 1/4 to the oil crankcase. I drove around on the interstate for 15 minutes or so and the light stayed on. On the way to work the next morning, to my disbelief and delight, the MIL went out!

Sorry I did not post this sooner. Injector cleaner, High Octane Fuel, Additives, None of these worked. Pulled the Cat off, bought the more expensive California Cat, problem cured! No codes! Fuel economy (34mpg Hwy) and power have not been a problem during this last episode. After installing the California Cat, it seems to run even better. California Cat has been on Vehicle for 45 days now.

Side note to the last post: I have read about alot of problems in this General Motors year range with gaskets and the new antifreeze, I think they chenged both the antifreeze and the gasket material now.

See www.catalyticconverterwarehouse.com (http://www.catalyticconverterwarehouse.com)

3rdmiller , try going to http://www.obd-codes.com/p0420 ! It gives info on code as well as causes and possible corrective measures , good luck !