How many oxygen sensor does my car have?

2001 CHEVROLET BLAZER
128,224 MILES • 4.3L • V6 • 2WD • AUTOMATIC
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LEOGEE3
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When I went to buy the sensors they said I had four, so I was like since I have the extra cash I’ll buy them. but when I was replacing them I only found 3,one on the driver side one on the passenger side and one maybe like the middle of the pipe..
Sep 25, 2020 at 7:36 AM
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STEVE W.
  • ✓ASE Certified Mechanic
  • 15,200 POSTS
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The stock system for the 4.3 will have 3 total, one upstream sensor (B1S1 and B2S1) on each exhaust pipe coming off the manifolds and then one downstream (B1S2) after the converter.
Depending on whose parts book they looked at it may list 4 though. I think that is because they are the same sensors that were listed for the 94 full sized Blazers and the company didn't change the information to match the S Series.
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Sep 25, 2020 at 8:23 AM
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