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1996 Cadillac Seville STS
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I'm preparing to change my 02 sensors. I've been getting the service engine soon light and service emissions systems. OBD2 code puller says I have 2 bad sensors, don't remember the exact codes. I've been looking for 02 sensors online and there is "upstream" and "downstream" 02 sensors. What is the difference? I've changed 02 sensors before, in other cars, so I know how to do it. But now I am confused with the upstream and downstream?? The dealer told me it would be 2 1/2 hours to replace them at $110 an hour. That's too much for a job I could do on my own. Could someone please advise me on exactly what I need...upstream or downstream? I can get the codes again if it needs to be done. Thanks
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Go to www.rockauto.com and get to your car, either engine, exhaust, or emissions, and look for O2 sensors. Click on the (!) icons or small pictures and they will expand into larger pictures of what you need.
 

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'98 STS (RIP @ 206,xxx miles)
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....I've been looking for 02 sensors online and there is "upstream" and "downstream" 02 sensors. What is the difference?
In aftermarket parts world terminology, it seems that "upstream" is before the cat. converter and that would leave one O2 sensor "downstream" of the cat. converter.

Prior to mid-year production of 1998, Cadillac used a total of four O2 sensors; one in each bank manifold plus one at the inlet of the cat. converter plus one at the outlet of the cat. converter. They could all be the same part number; but I cannot confirm that information.

The place I would go for (OEM) parts is
Palm Chevrolet Cadillac Saab of Gainesville
2600 N Main Street
Gainesville, FL 32609
352-376-7581
Cadillac Parts Department
Have your VIN available.
Mention that you are asking for web-sales price quotes.

O2 sensors is one of the parts where most folks would caution you against using aftermarket replacements.

And yes, you will need the codes to guide you on which specific sensors are "lazy".
 
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