When to replace 02 sensors?

[MH_Stevens]

My 2003 cruiser is at 260k miles is getting only 6 mpg and I suspect an 02 sensor (B2S2) is reporting rich with a lean condition so I'm going to replace it. At this milage should I replace both downstream sensors or even all four?

 

[Deflagrate]

I just replace them when they throw a CEL, but my cruisers have had a tendency to make me do them around the same time. Like I recently replaced my bank 1 sensor 2 because of a CEL, only to find out that it's apparently common to get a code for that sensor, but you actually need to replace bank 1 sensor 1 to get rid of the code. So now both sensors on bank 1 are new.

I've never had 6 mpg though. If you're getting a code for one (or more), definitely start there and see what improvements you get. They're all pretty easy to access, so it's not like the timing belt/water pump, where it doesn't make sense to not replace both at the same time. You could just order all four now, and replace them at your leisure or as needed.

 

[Octous]

I replaced all my O2 sensors at 298726 miles after getting an P0136 code.

 

[OEMGUY0720]

when they look like this

 

[Gozer]

I see a huge price difference with all the sensors from $30 up to a couple hundred each. Someone stole my cats and I need to replace the post-cat sensors as well now.

 

[MH_Stevens]

Thanks I'll do the four BUT I CAN"T AFFORD OEM right now so any aftermarket brand recommendations?
Have a Good July 4th y'all.

 

[OEMGUY0720]

Thanks I'll do the four BUT I CAN"T AFFORD OEM right now so any aftermarket brand recommendations?
Have a Good July 4th y'all.

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