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Discussion Starter · #1 ·
I have a 2001 with the 4.0 and I have had a check engine light in since I bought it the code comes back as a problem with a o2 sensor in the lower bank, well I just crawled under there cause I'm tires of looking at a check engine light, and I see there are 4 of them I see 2 looks like on the manifold 1 on each pipe after each small converter..... Is this all of them? I take it I have a California emission jeep also?? And one last ? Are these hard to take out and change? I'd there any tricks to doing this, or am I gonna have issues doing so? I have 135000 on the jeep that's why u want to just change them all. Thanks in advance
 

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You are correct, you have a California emissions jeep. All other exhausts only have 2 o2 sensors. o2 sensors are a PITA because with the constant heat expansion and contraction with cooling, they tend to seize into place and seize pretty bad. The best trick to removing them is to heat them up with a torch and use an o2 sensor wrench in order to break them loose.
 

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I was taught (for exhaust manifold but applies to O2 sensors too) to spray the bolts with WD-40 (PB Blaster works better) before driving in the morning and evening for a few days prior to beginning the work. Saturating the bolts (or in this case sensor) and then the resulting heat work to make removal a LOT easier.
 

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For a really stuck 02 sensor that you're going to replace, a standard socket is often required to remove it. Special 02 sockets with a slot machined into them to pass the wiring through will often deform due to that slot causing a loss of strength. So for when the 02 sensor is coming out anyway, cut the wiring off the top & just use a standard socket to remove it.

Heat will often work but using the longest wrench you can is also part of it. I had an 02 sensor that wouldn't (!) come out of my Toyota, I ended up having to weld a long extension onto the wrench to gain enough leverage to break it loose.

Finally, good penetrant products to help loosen seized hardware include Kroil, Break-Free, Liquid Wrench, and PB-Blaster. WD40 is NOT a suitable substitute for any of those despite WD-40's marketing department's claims it can do nearly anything and everything. I wouldn't waste my time even trying WD40 when a threaded part is seized in its threads. Technically speaking, WD40 is classified as a solvent.
 

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I agree on the WD....but, 30-years ago we didn't have nearly as many options. :)
 

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Soak it with PB Blaster and try renting or even buying an O2 socket since it's fairly inexpensive and use it with a breaker bar for leverage.
 

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How about just try to take them out first before going through all the trouble of buying/renting extra stuff?!?!? Mine came right out with a 7/8 wrench!! I know that's not always the case, but it is always a possibility.
 

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Discussion Starter · #8 ·
Ok thanks guys I appreciate the help. It's a Michigan jeep and been so for all its life so I'm sure it's gonna be the hardest worse scenario to, lol. I will soak all the o2 sensors for a week or so and then give it a shot. I am going to order these from rock auto, I was in there sure and there prices looked good but it's hard to read which ones I need I know the ntk but they call for up streams, down steams, bank 1, bank 2 what in the heck is all that about?
 

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Ok thanks guys I appreciate the help. It's a Michigan jeep and been so for all its life so I'm sure it's gonna be the hardest worse scenario to, lol. I will soak all the o2 sensors for a week or so and then give it a shot. I am going to order these from rock auto, I was in there sure and there prices looked good but it's hard to read which ones I need I know the ntk but they call for up streams, down steams, bank 1, bank 2 what in the heck is all that about?
Downstream are the two sensors closer to the tailpipe, behind the catalytic converter. I just did my downstream sensor on my '99 and it was an absolute bear. At the end of the day, it required an acetylene torch heating up the socket to cherry red and then using a big breaker to get it out, then finally cleaning up the threads. The upstream sensor on the other hand took all of five minutes to replace. In my opinion, I would replace all 4 sensors at the same time. If one's faulting, they are all probably not too far behind.
 
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