I have a 01 monte carlo ss 3.8 and I have the P0420 code which is catalyst efficiency below threshold (bank 1).

Im assuming if the o2 sensors were bad that they would have a 02 sensor code. I know I had 1 of the catalytic converters replaced under gms warranty a few years ago but Im over mileage now.

What is the 1st way to go about fixing this. Bank 1 I believe is the drivers side? Also if you think I should replace the converter is it hard to change? I seen this on ebay http://cgi.ebay.com/ebaymotors/Magna...Q5fAccessories

How hard are the bolts to come off. Im guessing I would need new bolts also right? Or am I better having a shop do this. Thanks

 

Also if I bought the magnaflow would I need to replace both converters, or just the bad one? Thanks

 

well first off that is for the 3.4 and replacing this is really easy to do. do you have emisions test where you live cause if you have to replace it you could go with the downpipe fromZZP they have the option to add the secondary o2 bank, or you could get teh high flow cat from them if the code would bother you. you might, might have to replace the bolts but probably not, just make sure you get new gaskets. but definatly check out ZZPerformance.
http://www.zzperformance.com/grand_p...ts1.php?id=551
i think that will fit your car, but ask around here. they have the options of rear o2 bank and high flow cat

 

both converters?? do you mean teh resonator?? im not sure, but i think you only have 1 cat, the thing behind it should be a muffler(resonator)(it keeps the drone out of the cab)

 

P0420 is the catalytic converter yes.

You only have one, because your car doesn't run true duals out the sides of the engine.

Go to a dealership and ask them if they will warranty the replacement of the cat, because they were recalled. Though they only do it up to a certain mileage... maybe 80k or 100k something like that. Ask them first. It would be free.

Do not buy that Ebay magnaflow cat, it doesn't fit your car AND the pipe is restrictive.

If you bought the downpipe with Cat from ZZP, the high-flow cat that is installed will still give you the P0420 code, so that won't really solve your problem... but you can then get a PCM with that code deleted?

I would just start with trying to get it fixed for free, don't let them make you pay for it, because it will be almost $400. If it can't be fixed under recall, then I would start modding the car haha