P0328 and P0420 - 2004 SE/SC

[MichiganMan]

Truck is throwing P0328 (knock sensor) and P0420 (cat) both on bank 1. 140K miles, timing belt done 5K miles ago, fresh plugs, wires, and dist. Dealer wants $105 just to look at it and money is tiiiight right now. If it is a cat, I'd prefer to go to an aftermarket shop that will use aftermarket parts, but I'd like to have a bit more confidence that this is actually causing the problem. Truck does seem to idle rough until it throws the codes.

Any thoughts or guidance would be appreciated!

 

[Roadwarrior]

Knock sensor code gets thrown if you hit a bump too hard. It could be worth ignoring that.

Were you doing anything to cause the code? I threw a MAF and KS code today going through a deep puddle. Quick cleans and a fix.

 

[MichiganMan]

Nothing but normal driving. It has been throwing these codes off and on for a while. Clear it and it is good for a few months/weeks, getting more common now. Figured it was time to fix it once and for all.

 

[Muadeeb]

p0420 is the front cat not working right. Usually, I just take the rear sensor, put it in a CEL eliminator (or spark plug non-fouler) to move it out of the exhaust pipe a bit and call it a day. You are right that it is Bank 1, and that is on the passenger side of the engine for us.

As for the p0328, I'm with RW, in that I usually ignore it. Being that you're Supercharged, it might be worth your time to relocate the sensor, as they tend to fail easily and put the SC into a limp mode.

 

[MichiganMan]

Local exhaust shop with a good reputation thinks he can replace the cat with a "universal" model for about $250. I'm tempted to go that route, but don't know squat about exhaust. Is there anything magical about the cats in there? From the dealer prices, you'd think they are made of 100% pure unicorn crap and coated in platinum...

 

[Muadeeb]

Well, they _are_ coated in platinum, but I'm doubtful on the unicorn crap. I'd go the muffler shop route over a dealership any day. The biggest issue is that, depending on the run, your cat may be integrated into the header and they are a b¡tch to get to.