Plugged converters??

I'm working on a 2004 silverado p/u with a 4.3 engine.The check engine light is on giving me codes PO420 and PO430.The service manual that I have is for 1997,but I believe that it will apply.It tells me that the converters are not changing the exhaust gases into safe gases.The second oxygen sensor is used to monitor the converters performance.If the converter is not functioning properly,the codes mentioned will trigger the check engine lite.Has anyone come across this situation and what was the end result?What causes the converters to fail when the vehicle has only 71,000 km?I can't imagine the replacement cost for converters will not be cheap.
The fuel pump and filter were recently changed.I don't believe this has anything to do with it,but I thought I would mention it. I don't want to change the converters without more info.Any tests that could be preformed?The vehicle runs,but it just doesn't have the pep it used to.Any help would be greatly appreciated.
chuck's

P0420 - Catalyst system efficiency below threshold, left bank.
P0430 - " " " " " " '" ", right bank

The sensors could be bad, do a search for o2 sensors as these codes pop up on this forum enough that you will find different approaches to fixing it.

I would take the converters off and take a 5 lb sledge and a steel rod and break the guts out of them and bolt them back up,,,If the truck has a good tune up on it at time of inspection it will pass and they have no way of telling that the converters have been hollowed out it will also increase you H.P. ,,it gives the exhaust an expansion chamber and will run 100% better

An expansion chamber? Why would a vehicle need this? I'm about to remove mine as soon as my new tune gets here, and I was just going to cut them off and put pipe there. Is that not a good thing to do??

How much back pressure does your engine require and can it work without the cats??????

you can not remove the cats. if you do the same code will set and or activeity code for post o2.

Im not worried about the codes, as I have my rear o2's switched off in my PCM.

Call Allen, he will definitely know more....

I just told him to cut the rear o2's off because I'm ditching the cats as soon as my new pcm is here.

For anyone interested,it seems that one of the converters was plugged.Not sure of the other one ,but I don't think that the other one was all that healthy.I never got an answer why but it appears that the oxygen sensors were fine.
chuck's

DId it help your mileage or power at all????

YES!!!Most definitely.Prior taking it to the dealer the vehicle would do 30mph top speed.It would go a little faster down hill and with the wind.
chuck's

LOL. I can tell I need to remove mine then. Mine will still do well over 100mph, but I just feel they're clogged. It feels sluggish and like it's having a hard time accelerating sometimes.

These converters appeared to clog over time.A little worse as time went by.They didn't clog overnite.Before they got worse,the vehicle would do 60 mph, but if you wanted a little more speed,it just couln't do it.Now this vehicle had a 4.3 ltr v-6.Yes it did seem to have a slow acceleration response.You could try to lossen the Y-pipe from the manifolds and check the vehicle performance.Also monitoring your engine vaccum will also help.
chuck's

The emissions system in your truck has a 8 year/80,000 mile warranty and the cats are included. Take your truck to your dealer and if it needs the cats replaced, it will be done free of charge.

This warranty includes all parts of emissions equipment including computers and sensors.

The 8 year/80,000 mile emission warranty is mandated by the federal goverment.

I am suspecting a similar problem in my 2000 with the 5.3L. Can the cats be repaired or do they have to be replaced?

Thanks!

The emissions system in your truck has a 8 year/80,000 mile warranty and the cats are included. Take your truck to your dealer and if it needs the cats replaced, it will be done free of charge.

This warranty includes all parts of emissions equipment including computers and sensors.

The 8 year/80,000 mile emission warranty is mandated by the federal goverment.

too bad mine has 120K on it!! lol
Damn!

Im not worried about the codes, as I have my rear o2's switched off in my PCM. How do you switch off your rear o2s at the pcm?

Not to be nitpicky, b/c I definitly don't care and would do the same if needed, but you should probably warn people that hollowing them out or disabling the cats is likely illegal. So, you know, we are not to be held liable.......... and all that crap.