O2 sensors, replace both front and rear? (1 Viewer)

[SICARIO]

I just replaced both of my rear O2 sensors. I was getting a P0420, and I figured if I was replacing one side, I might as well replace both. It fixed the check engine light code and my voltages appear to be nice and steady in the rear.

Should I apply the same logic to the front sensors (replace them since I replaced the rear)? They seem to be cycling their voltages like normal, but the are as old as the rear sensors.

I know if you change one spark plug, you should change all. Not sure if this logic also applies to the O2 sensors.

 

[outdoorsman]

It is never a bad idea to change O2 sensors if you have high mileage on them especially if you can change them yourself.

I would make sure to use quality replacement sensors. Then they should last a long time.

 

[mrbigboy]

I would replace individual sensors when they fail. The spark plug logic does not apply to 02 sensors.

 

[Spike555]

I always replace O2's in pairs, rears at the same time and fronts at the same time but I only do that when they throw a code.
Now to be 100% by the book there is a life expectancy for O2's, usually around 90k, my wifes Volvo had a O2 change light that told you when to replace them based on mileage.

Rear O2's literally do nothing other than tell you if the cats are working properly or not.
So on the rears you can go ultra cheap.

Marginal front O2's can effect MPG.

The front and rear O2's are the same, you can swap the used front's to the rear and put the new rears in the front, that would actually be the best use of your money.

 

[JPS]

Nobody uses O2 spacers o on the rear and just replace the fronts?

 

[pjm10626]

Ive got a code for the passenger rear, since its useless in theory, is there a way to bypass the sensor so the CEL will stay off? I keep the ob2 scanner in my LX to clear it whenever it pops up, but that's nearly everyday.

 

[Spike555]

Nobody uses O2 spacers o on the rear and just replace the fronts?

Those who know do.

Ive got a code for the passenger rear, since its useless in theory, is there a way to bypass the sensor so the CEL will stay off? I keep the ob2 scanner in my LX to clear it whenever it pops up, but that's nearly everyday.

That's what the spacer is for. The O2 must be in place, if you unplug it you'll have a constant check engine light.
If you take it out of the exhaust and leave it hanging, you'll have a constant check engine light.
It must rear exhaust, but the spacer pulls it far enough from the exhaust stream so that a bad cat will not set off the CEL.

Now, if the O2 is bad you will get a CEL even with a spacer.

 

[SICARIO]

Underdog racing makes a bypas simulator, though it’s more expensive than two new o2 sensors. ($150 vs $90). I think unless I has a sweet custom exhaust that required the simulator, I’d rather just replace the sensors.

 

[Spike555]

Underdog racing makes a bypas simulator, though it’s more expensive than two new o2 sensors. ($150 vs $90). I think unless I has a sweet custom exhaust that required the simulator, I’d rather just replace the sensors.

It's more than just replacing the sensors though. If the cats are bad the O2 simulator is a great way to go if you cannot use the spacers because of emissions testing.
A good emissions test person would notice those and fail you, the simulator, if you install it correctly, you cannot tell it is there with a visual inspection.

Why would someone do this instead of replacing the cats? Because the cats cost as much as a house.

 

[pjm10626]

Where do we get these spacers? I don't have emission testing where I live so I've got more options that most.

I just bought the LX less than a month ago, the dealer I bought from jsut replaced the O2 sensor causing the CEL to go off. I crawled under there to verify, and the sensor is new.

 

[jerryb]

in 2005 they swapped to wideband upstream, they are not all the same. 03 and 04 yes, the rest post 05/2005 are WB upstream.

 

[Biga27110]

in 2005 they swapped to wideband upstream, they are not all the same. 03 and 04 yes, the rest post 05/2005 are WB upstream.

Thanks for the info that is pretty huge for those of us 05+

 

[jerryb]

now that I think about it, that's when variable valve happened, I think? If ever In doubt check techstream of torque or fusion on 02 voltages. I think toyota is either 3.3 or 3.2V for reference signal on WB.

 

[Biga27110]

now that I think about it, that's when variable valve happened, I think? If ever In doubt check techstream of torque or fusion on 02 voltages. I think toyota is either 3.3 or 3.2V for reference signal on WB.

06+ has VVTI, ill check my tech stream