The Infamous O2 Sensor

FadeToGray

FadeToGray

TJ Enthusiast
Supporting Member
Joined
Feb 4, 2019
Messages
192
Location
NH
While driving today I had my engine malfunction light come on, and my ODB2 scanner is reporting "Warm Up Catalyst Efficiency Bank 1 Below Threshold".

This is on a 2005 LJ with 196,000 miles.

Looking through the paperwork that I received from the previous owner, it looks like that at around 184,000 miles, the Bank 1 O2 sensors were replaced.

The brand used by the repair shop is "Delso".

After scanning the forums here it seems that NGK / NTK is all that should be used.

My question is do you guys think I should just replace those 2 O2 sensors again using NGK / NTK ones.

Or is it more likely to be the catalytic converter itself, and I'm wasting my money replacing the sensors?

Thanks!
 
With that kind of mileage it could be either. I would swap the sensor causing the code with an NGK/NTK first.
 
All of the O2 sensors should be replaced at once, even if only one of them is throwing the code. O2 sensors are a standard wear-and-tear maintenance item, and generally you want to replace them all around 80k miles give or take. That will keep the engine running optimally.

As you noticed, the only brand you want to use with our TJs is NGK / NTK. The other brands are known to throw codes even when there is nothing wrong with them. There is a good video explanation of why this is in The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread.

With as cheap as they are (and given your mileage), I would replace them all. You can also find the links (and part numbers) for the correct sensor for your year and model of TJ in that thread I linked to above.
 
I replaced all 4 sensors with the NGK / NTK ones and it seems to have fixed the problem. Thanks all!
 
I just replaced the catalytic converter on my sons 2005 TJ. It really was the cat. The reason I even mention this is that the price on Amazon is WAY cheaper than the local part stores. I don't know if Amazon is making a mistake or what. The price as of this writing is $473 at Amazon and $799 at Advance Auto Parts.

https://www.amazon.com/gp/product/B0027A6PAA/?tag=wranglerorg-20

Anyone wanting to change the cat with a similar year TJ, this seems like a good deal.
 
FadeToGray said:
My question is do you guys think I should just replace those 2 O2 sensors again using NGK / NTK ones.
Click to expand...


Yes, I would. They are cheap enough that it's a no brainer if you ask me.

It could be the cats starting to fail, but that's over $300 to address, whereas the O2 sensors are around $30 a piece.

However, it's a smarter idea to replace ALL the O2 sensors at once, as O2 sensors are basic maintenance items that should ideally all be replaced at the same time for optimal engine performance.
 
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