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Pre-cat oxygen sensor?

1K views 5 replies 2 participants last post by  autoque 
#1 ·
The ones that are changed when something is amiss, which are they?
 

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#2 ·
you change them when they are causing issues... not guessing what is causing a transient 300 rpm blip on cold start up.

looks like the first one.
 
#3 ·
Yeah, well, I'm desperate. The vehicle has a three year old issue. This will likely be my last try before I give up and just live with it. Painful, but knowing I did everything I can, at least I'll have no regret.

Shouldn't it be the first one AND the second one as well? I thought they go in pairs.
 
#4 ·
I think there is one pre-cat (which is what you asked) and one post cat sensor.

Has anyone confirmed that what you are seeing is 'real' or abnormal? And not us idiots on this forum... mechanic, tech, etc?

A
 
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