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2005 CTS 3.6L
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Discussion Starter #1
Ok, I've had a p420 code for a bit and have delayed the inevitable repair. Now coming home today on the expressway, something went and the exhaust is very loud on the front right side of the car(same side as failed cat). I need to get under there when there's more light out, but I'm thinking the exhaust manifold or something before the catalytic converter finally fully cracked open. Please advise if you have encountered this issue before. I'm guessing the rattle in the cat was probably a piece from this.

Car info: 2005 CTS 3.6L

Thanks ahead of time!
D
 

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"Angel Dust" 2004 White Diamond CTS 3.6L-V
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Ive got the same code...delayed the repair on my passenger side forever...I went to merge onto the expressway and the cat literally rusted out/cracked at the top flange and left my exhaust hanging and scraping...sparks and all...lmfao. Drove home on local roads with pretty much an open header, scraping exhaust and hazards...had my repair shop tack the cat back as much as they could but, I'm still getting the CEL/MIL, a little salt & pepper air leak sound and horrible gas mileage...
 

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2005 CTS 3.6L
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Discussion Starter #3
Thanks for the info. All I'm reading is the replacement of the CC. Is this something we can do ourselves? i.e. no welds. I need to get to work tomorrow with it like it is, but will take to a shop if needed sometime during the day. But, if I can drive with it for a bit for now(as loud as it is), and can replace it myself, then that's what I might do to save some $. If not, then muffler shop here I come.
 

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"Angel Dust" 2004 White Diamond CTS 3.6L-V
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Well I'm driving mine with the temp fix myself...only due to the fact that my one side blew off...but, I'm told/advised to change BOTH at the same time to avoid the other side clogging and/or rusting out and having another situation, loss of performance, back gases into the block, etc. That would be close to 600.00 in parts without labor from my shop...then I thought to myself, oh...lets go universal Magnaflow Hi-Flow...which is cheaper than oem but, I'm reading that some peoples vehicles still throw a code on the rear o2's...and in NY we have safety AND emissions inspections. That wouldnt let me pass with flying colors at all. My next thought was to get used oem's and gut them...might still throw a code but, an even cheaper solution. Not that I'm trying to cheap out on this but, I wouldnt mind a bit of performance flow either...Called around to some salvage yards...they got 'em but, its illegal to sell them "used" lmfao...guess I have to pay them a visit with cash in hand and no receipts...
 

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2005 CTS 3.6L
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Discussion Starter #5
I'm in FLORIDA so no emissions tests. I may go with a cheaper cat that has some warranty as my cts has 155k on it already. I'll get some quotes tomorrow, so we'll see.
 

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"Angel Dust" 2004 White Diamond CTS 3.6L-V
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I'm in FLORIDA so no emissions tests. I may go with a cheaper cat that has some warranty as my cts has 155k on it already. I'll get some quotes tomorrow, so we'll see.
:canttalk: @ Florida...lol
 

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2005 CTS 3.6L
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Discussion Starter #7
So, I just received a quote and all they say is available that's direct fit is the OEM part and with labor it'll cost me $695. That's a little more than I wanted to spend. Anyone recommend or know of an aftermarket Direct Fit Cat for the 2005 CTS 3.6L?
 

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2005 CTS 3.6L
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Discussion Starter #9
How difficult or easy would it be do replace myself? I'm going to put my car on ramps tomorrow and get underneath to make sure that's the only damage visually. I'm more worried that the bolts are rusted and all locked up. We'll see after I inspect again.

Thx for the Rock Auto info. I hope they truly fit.
 

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2000 Escalade, 2006 CTS, 2008 SRX
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Please post what you found out about the RockAuto replacements and how hard it was to do it yourself. I am gonna have to do it in the next few weeks.
 

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2004 CTS 3.2L M35 LtPt
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244 Posts
On my '04 3.2, heck, the passenger cat fell out by itself last time I had the drivers' side out for the crank position sensor swap (stupid busted welds). Fortunately I have a TIG welder in the shop...

Soak the bolts the night before in something like PB Blaster, and then take them apart the next morning. Won't be too hard at all. All you should need are some deep sockets and some socket extensions.
 

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2005 CTS 3.6L
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Discussion Starter #12
So, I got under my car yesterday and found that the cat might be ok. Problem is the cat clean cracked at the front mount point. This morning I brought to my local muffler man and he tack welded for now since he can't get fully around for a good weld. Issue is in order to get to it, you have to go from the top or at least get the heat shield off. PITA! But, he's a bargain price wise, so we'll see if it takes less than 4 hours. However, something is still causing a rattle at random times, so I'll be searching tonight with the rubber hammer. $20 for the tack weld job and he's estimating me about a buck fifty for the bigger job($150). BTWm cabletech, would definitely need PB Blaster on the O2 sensors....holy cow they're heated tight!
 

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"Angel Dust" 2004 White Diamond CTS 3.6L-V
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Replaced both of mine with Magnaflows 99205HM Universals..codes cleared and no problems so far....200+/- miles so far.
 

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Replaced both of mine with Magnaflows 99205HM Universals..codes cleared and no problems so far....200+/- miles so far.
Any increase in power hp torque? Im assuming magnaflows have better flow than oem i mean deff could be wrong. Hows it sound too?
 

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"Angel Dust" 2004 White Diamond CTS 3.6L-V
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Def. A noticible torque increase and she pulls way harder. The sound at idle is a bit louder and at wot very deep...probably due to my pipe size and borla's however. Still breaking in the cats though.
 

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2005 CTS 3.6L
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Discussion Starter #16
RCVW- what site did you buy the magnaflows? I want to make sure I'm getting the right part. Is the passenger side part # different than driver side for this one? I'm seeing a 99204HM for just under a bill. Thx ahead of time!

D
 

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"Angel Dust" 2004 White Diamond CTS 3.6L-V
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RCVW- what site did you buy the magnaflows? I want to make sure I'm getting the right part. Is the passenger side part # different than driver side for this one? I'm seeing a 99204HM for just under a bill. Thx ahead of time!

D
Used the same part on both sides...ordered from Summit via eBay. My shop cut out my old cats, left the flanges intact and welded in the universal magnas...
 

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2005 CTS 3.6L
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Discussion Starter #18
I believe the difference in part number is due to yours being a 2004 vs my 2005. There could be a diff in pipe diameter.

Thx again
D
 

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I just bought 299204HM.. I got them today and found out they sell OEM grade... I'm pissed cuz I'm thinking these will still throw a cel.... Should have got hi flows if that was the case.. Now I'm thinking about going catless... You guys that installed these did you end up get a cel?
 
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