Need O2 sensor replacement advice

[rol1964]

I have the 0138 code (CEL was intermittent but now appears to be more "on" than "off") on my new to me '04 TJ 4.0 135000 kms / 80000 miles.
I read somewhere that it's best to replace O2 sensors in pairs i.e.: both downstreams or both upstreams or all four at any time you replace.
So is it wasted money to just replace one sensor? I will order NGK's once I figure this out. Thanks Rol1964

 

[TheBoogieman]

It's not a waste of money if you replace the one that is actually bad. Bad upstream sensors will kill your gas mileage.

 

[Jerry Bransford]

NTK is what you'll find most commonly, NGK is pretty rare... they're the same since NTK is part of NGK.

You can get them from https://www.rockauto.com/en/catalog...01,exhaust+&+emission,oxygen+(o2)+sensor,5132

NTK: (for 2004 4.0)
23137 1-3 Upstream
23132 1-3 Downstream
23135 4-6 Upstream
23531 4-6 Downstream

Make sure you stick with the NTK brand.

 

[L J]

They are so inexpensive (~$100 for all 4 using RockAuto and the discount code) that unless you're really strapped for cash I'd just replace all four.

 

[R.Flores]

NTK is what you'll find most commonly, NGK is pretty rare... they're the same since NTK is part of NGK.

You can get them from https://www.rockauto.com/en/catalog...01,exhaust+&+emission,oxygen+(o2)+sensor,5132

NTK: (for 2004 4.0)
23137 1-3 Upstream
23132 1-3 Downstream
23135 4-6 Upstream
23531 4-6 Downstream

Make sure you stick with the NTK brand.

Thanks Jerry, you just made my day. I had a mental mess on this issue.