New from the dealer is less than $700+labor. Labor is 5 stud nuts and 2 O2 sensors. I don't know why anyone would charge more than an hour, I do it laying on my back in a half hour. Done it 5-6 times this year.

I just remembered $15 for gaskets

http://www.gmpartsoutlet.net/auto-parts/2009/chevrolet/hhr/ls-trim/2-2l-l4-flex-engine/exhaust-system-cat/exhaust-components-scat

 

I've often wondered why they have 2 seperate part numbers for the auto and manual. There is no difference in the exhaust from what I could find.

 

Some have the #1 sensor on the manifold some don't have the second cat. The drawing is generic.

 

Put one of these on. The PO420 code will go away.

http://www.bigdaddiesgarage.com/straight-cel-fix.html

 

unless you need an emissions test.

And only worked for me one drive cycle.

 

Ya, that's true. I don't in Michigan.

 

well, spent the $700 and now the engine runs much better. Me and the mechanic think the cat failed because of the tank of diesel we ended up with cause the idiot fuel truck driver pumped diesel into the regular gas tank. It took several years though.

Before the new cat it surged at low speeds and seemed like it took a lot of pedal to kick down to get up to speed getting on the freeway. Kicks down better now.

We live in a gated RV (trailer) park (yes gated) where the speed limit is 10 mph, trying to keep it down to 10 was hard, give it a little pedal it would surge up too fast, had to let off, too slow, so pedal again surge & speed up again. Now just idles steadily along (idles about 10 mph).

(No emissions testing here in NW Washington)