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Cadillac
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Discussion Starter #1
I need to replace the oxygen sensor in my 01 SLS, and am not a super car guy. Any advice? I've replaced them on Buicks in the past, so I know I can do it, but with this massive Northstar engine packed into such a small space, I do not even know where it is. Can anyone give me some guidance one where it is located and what steps I need to take to get to it? Or is it buried so far in there that I should pay someone to do it. Any advice would be appreciated. Thanks all.
 

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'98 STS (RIP @ 206,xxx miles)
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4,854 Posts
There are (at least) three O2 sensors for your model/year engine; which one are you planning to replace?

And why?

What codes are being set?
 

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Discussion Starter #3
Unfortunately, I do no know which code it showed, the guy at AutoZone checked for me. I assumed I'd need to replace all of them (thought there were two, I didn't know there were three). Should I replace all 3 for good measure?
 

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White Diamond '03 DHS (with DTS floor shift)
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86,994 Posts
No. Pull the codes yourself. There is a "sticky" in the Tech Tips section that will tell you how to do it.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Go through the archives and search functions in the headers of these pages. O2 sensors are well covered. 1 in the collector of each bank and 1 after cat. Learn how to pull your own codes and find the parts on the recommended sites. If you've done exhaust/sensor work, it's a piece of cake.
 

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Discussion Starter #6
Thanks for the info guys. I just got around to pulling the codes this morning. The two current codes are:

PCM P0171
PCM P0174

What I can find on these codes (combined with what I've been reading in other threads) is that it system is running lean. Is this an O2 sensor after all, or do I have a different problem? Any advice would be awesome. Thanks again.
 

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White Diamond '03 DHS (with DTS floor shift)
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Lean usually indicated a vacuum leak. Since it is both banks I'd check the "plenum". That is the rubber coupler between the TB and the manifold. Seems to be a somewhat common leak point.
 
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