Catalyst Converter Problem....

[HUMTECH]

You can but o2 sensor cheaters to install after the cat which will tell the pcm everything is normal. If you need to pass a smog test you will fail though. I put them on my 98 Z71 pickup and they work great. Not positive if they are avail for the Hummer, but def worth it. With an open cat it will think your running rich and the pcm will pull fuel trying to correct, or unplug the post sensor and it will run in open loop

[IRA51]

gutting the cats and useing Sims to repace the down stream O2s works great ,if you don't mind breaking the fedral law on cat tampering/removal. getting new high flow cat's is a far better idea.

[HUMTECH]

High flow Cat? The backpressure rating on a stock gm cat is 0.5 psi max. I think they flow pretty good

[IRA51]

the Random tec cats and the Magnaflow cats are cheaper that the factory cat ,and flow as well or better . I was under the impression his was bad.

[8500lbs]

I have the Dyna Tech high flow cats and I have less than 50,000 miles one them. I thought they were great untill yesterday when they tripped the engine light three times. it is P0420 or insufficient flow. Not sure what the deal is but i am going to try and call Dyna tech and have them replaced. ig it is a no go then i am going to strip them and look for the censor chearters. Does any one know or recomend a place to get them from,

Thanks
B

[IRA51]

a P0420 is bank 1 I think and it could be anything from an exaust leak to a bad cat . some times a bad O2 can set it . if the down stream O2 does not see much of a reduction it can set it . I would check the O2's first to see if they are good B4 changing the cat .check your coolant level,a leaking head gasket can kill cat's and O2's .

[HUMTECH]

Originally Posted by IRA51

a P0420 is bank 1 I think and it could be anything from an exaust leak to a bad cat . some times a bad O2 can set it . if the down stream O2 does not see much of a reduction it can set it . I would check the O2's first to see if they are good B4 changing the cat .check your coolant level,a leaking head gasket can kill cat's and O2's .

Correct, p0420 is bank 1 catalyst low efficiency. Outside chance that an o2 sensor will set this code, but is possible. Also needs a pretty good exhaust leak, at least one audibly noticable to set it. But still possible for sure. As said above, check for exhaust leak, o2 scan data would help, but in the end my money would be the cat is bad. In my experience i have never seen a low catalyst efficiency code set that a new converter didnt fix. I even gambled on a couple that had headers installed that were leaking badly and turned out the new cats fixed them.