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Old 11-09-2010, 05:31 PM   #1
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Default 2 o2 sensors?

I was checking 02 sensor prices and I noticed some were upstream and some downstream I've only seen the one infront of the firewall(upstream I would assume). Is there a downstream sensor that I haven't seen?


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Old 11-09-2010, 06:34 PM   #2
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in the cat
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Old 11-09-2010, 06:34 PM   #3
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After the cat
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Old 11-09-2010, 06:35 PM   #4
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oops sorry, just after the cat to be more precise IIRC
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Old 11-09-2010, 07:18 PM   #5
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After the cat and it'* the upstream one that is the problem maker. The down stream O2 checks to see if your cat is working properly
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Old 11-09-2010, 07:25 PM   #6
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Son of a crap! A buddy of mine scanned the car and said my check engine light was on most likely because of a bad o2 sensor. I thought there was only one.I changed the upstream about four years ago .Do you guys know what code a bad o2 sensor would throw?(I assume both o2 sensors would throw the same code)
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Old 11-10-2010, 11:00 AM   #8
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Thanks Dan I'll ask my buddy for the specific code, thank you sirrrrrr.
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Old 11-11-2010, 11:01 PM   #9
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Ok it turned out to be the downstream sensor I changed that yesterday,but today the check engine light came back on. So I had it checked at Autozone and the guy said it'* code p403 and p404 and then he said possibly a bad EGR. Is there anyway the EGR code could be related to the o2 sensor I just replaced? And is it normal for both 403 and 404 to pop up at the same time?

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Old 11-11-2010, 11:18 PM   #10
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It could be a sticking EGR pintel. Can you hear it click when you unplug it?
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