Before you replace O2 sensors

AndyG

AndyG

Because some other guys are perverts
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O2 sensors get talked about a lot on here.

What doesn't get a lot of mention is loose exhaust at the pre cats - those 4 bolts you access from below that hold the exhaust together between the upstream and downstream sensors.

Any leak there confuses the sensors and they will code.

I have fixed 2 TJ's with sensor codes by tightening the bolts- they will feel frozen at first and to some extent are....but can still be quite loose.... They tend to work loose a little bit and then a little bit of corrosion sets in around the bolt and it locks a little.

This isn't the answer to everyone's oxygen sensor problems but it needs to be pretty high on the list.
 
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Good suggestion. Before trying to tighten those particular bolts it'd be wise to hit them with a couple healthy sprays of Liquid Wrench, Kroil, or Break Free first and give it some time to work before applying the wrench.
 
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02? You mean O2?

Haha, I fixed it for you. Not sure what a ZERO 2 sensor it ;)

Sorry, I couldn't resist :ROFLMAO:

Great suggestion though!
 
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Jerry Bransford said:
Good suggestion. Before trying to tighten those particular bolts it'd be wise to hit them with a couple healthy sprays of Liquid Wrench, Kroil, or Break Free first and give it some time to work before applying the wrench.
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Excellent addition Jerry....I think one thing to consider is if the vehicle codes on initial startup that's a pretty good indicator that it just pulled in some cold air...

Just for the general knowledge base if I understand it correctly the upstream and the downstream work together to monitor the job the cats are doing.... I would think whatever parameters that they are set for would be fooled by the intake of cold air at startup.

Please don't take my word as gospel that's just what I think happens .
 
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