2005 2500HD 6.0 - Troubleshooting P0300 Codes

[chev78fan]

I finally found the time to remove the cats - driver side good / passenger side plugged solid.

 

I have "test pipes" in for now and it runs great!!

[chev78fan]

I'll upload a pic soon.....

[chev78fan]

[Jsdirt]

What in the hell is all that? From here it looks like the thing had a blown head gasket, or a few pistons with no rings at all ...

[Chris]

The cat is just completely degraded

[Jsdirt]

Never seen one do that before. All the ones I've seen melted. That one there looks like a pile of carbon inside with intact honeycomb underneath.

 

Must be my computer screen. Pictures sometimes aren't what they appear on this thing ...

[Duelin]

Just remember when one cat is good and the other one looks like that. There is an underlying reason for it being that way.

[chev78fan]

The unit at the top of the picture is the driver side - when held against a flashlight you can see thru the honeycomb.

 

The unit at the bottom of the picture is the passenger side. The inlet is facing the camera. The outlet side still has the honeycomb intact. The inlet side is completely clogged and the honeycomb has collapsed/crumbled into what looks like sand. The "sparkles" are shavings from the sawsall.

 

I believe the cause was a bad set of spark plugs.