[AVR2]

Does anyone change their O2 sensors as part of routine servicing? Supposedly they should be done about every 100k miles.

Or do most people wait until they start throwing codes?

I've just replaced both my upstream sensors to fix a P0152; only the bank 2 sensor was affected, but I read in several places that it's best practice to replace them in pairs to avoid ending up with one new sensor and one older "lazy" sensor.

So now I'm wondering whether I should go ahead and replace both the downstream sensors, just because I don't know how old they are?

 

[Bigrigr]

Not necessarily a bad idea to change them at 20 years old, I have heard of people claiming that their fuel mileage went up when they did this. Havent done it myself though...

 

[GTP231]

Might as well as it could lead to P0420 and 430 codes being set for the same reason you replaced both fronts

 

[GmanWJ]

This is how I understand O2 sensors.



The upstream sensors are used to control fuel trim. Their voltage output is constantly changing and require rapid response; if they cannot keep up then they are not doing their job. High stress situation.



The downstream sensors are there to determine if the catalytic converters are operating. They are essentially constant voltage output; all they need to do is provide a flat voltage reading. Low stress situation.



Of the two, the upstream seem more likely to fail. As long as the downstream are producing spec. voltage, why bother replacing? You would be putting in aftermarket sensors that have an iffy reputation to replace something that is currently performing a simple task with no problems. I don't know, does not seem worth the risk to me.


Please somebody correct me if I am wrong.

 

[HampshireWJ]

No.
Prevantative maintenance is about doing stuff that are service items - oil, filters, fluids etc that are shown in the maintenance schedules. Stuff like brakes, wipers, sensors, gas struts, ball joints, tyres, and handbrake adjustments etc, are things that we should keep an eye on and do when they need doing.
The sensors either work or they don't, sure they give up after a while but no point in replacing them just because they are a 'bit old'. You car will even tell you which one is faulty when the time comes.
If your vehicle is running fine and not throwing codes since you replaced the sensor, I cannot see a reason to replace the others - do them when they give you problems. These are my thoughts on the subject.

 

[Bigrigr]

This is how I understand O2 sensors.

The upstream sensors are used to control fuel trim. Their voltage output is constantly changing and require rapid response; if they cannot keep up then they are not doing their job. High stress situation.

The downstream sensors are there to determine if the catalytic converters are operating. They are essentially constant voltage output; all they need to do is provide a flat voltage reading. Low stress situation.

Of the two, the upstream seem more likely to fail. As long as the downstream are producing spec. voltage, why bother replacing? You would be putting in aftermarket sensors that have an iffy reputation to replace something that is currently performing a simple task with no problems. I don't know, does not seem worth the risk to me.

Please somebody correct me if I am wrong.

This is very true Gman, excellent point. One might gain on replacing the lazy upstream sensors, but the rear sensors are basically just monitoring the catalytic converters efficiency. they have very little(if any at all) effect on fuel mileage or how the engine runs...My mistake.....

 

[SD Overland]

I had my B2S1 replaced about 2 years ago to fix a P0174 code. I have always considered just doing the rest of the sensors eventually, but I'm surprised to see I've apparently been considering about that for 2 years now!

 

[UKXJ]

I now know more about O2 sensors than I ever did - thanks Gman - but still really none the wiser as to what useful purpose they serve. So, absent any symptoms affecting driveablity, would still only replace one (or more) if necessary to knock out the CEL - just to get through inspection.

 

[AVR2]

You would be putting in aftermarket sensors that have an iffy reputation

No, I would only use NTK, which are the factory OEM. Exact same sensors you'd get from the dealership, but much cheaper because they wouldn't be in Mopar packaging.

 

[JoMc67]

Well, if we are talking preventive maintenance, then minus well replace most all other Sensors with Mopar equivalents...TB, Tranny, Brake/ABS, etc, etc, spending upwards to a $1K worth of Sensors.

I'm in process now, and about half-way there...

 

[wranglertec]

Under normal circumstances no. Jeep never recommended them as normal service. But I’ve seen adds by aftermarket parts manufacturers stating replace your O2 sensors at every 50000 miles.


Sent from my iPad using Tapatalk

 

[fmradio516]

Related topic: is it really necessary to replace the O2 sensors even when they start throwing codes? I have just been clearing the codes whenever they come up. Sometimes they come back quicker than other times. Just seems like a lot of money to spend on very little reward.

 

[GmanWJ]

Related topic: is it really necessary to replace the O2 sensors even when they start throwing codes? I have just been clearing the codes whenever they come up. Sometimes they come back quicker than other times. Just seems like a lot of money to spend on very little reward.

Upstream sensors throwing codes then yes because they affect how the vehicle operates. Downstream sensors seem like they are just there to tell you when your cats no longer work, so the only reason to replace them would be if you care about how much pollution you are dumping into the atmosphere. I think.

 

[fmradio516]

Upstream sensors throwing codes then yes because they affect how the vehicle operates. Downstream sensors seem like they are just there to tell you when your cats no longer work, so the only reason to replace them would be if you care about how much pollution you are dumping into the atmosphere. I think.

Thanks, yeah that makes sense. And I just realized that the O2 sensors are much cheaper than i remember. I thought they were around $50, but looks like Rockauto is MUCH better. So ill be replacing my upstream one that keeps throwing codes!

 

[UKXJ]

. . . I've seen adds by aftermarket parts manufacturers stating replace your O2 sensors at every 50000 miles. . .

Well of course - they've a product to sell! They'd say every 15,000 miles if they thought they'd get away with it.

 

[UKXJ]

Upstream sensors throwing codes then yes because they affect how the vehicle operates. Downstream sensors seem like they are just there to tell you when your cats no longer work, so the only reason to replace them would be if you care about how much pollution you are dumping into the atmosphere. I think.

As it seems you don't have to interrogate a WJ for codes (didn't have mine long enough to find out the hard way) that might change my generally anarchic views on the subject, although I'd like to think I'd know there was something wrong without a code (which should tell you what is wrong, not just that something is). If I really cared about pollution I'd not be driving any form of 20+ year old Jeep - but I'm content as long as it passes inspection. Mind you one of my XJ's doesn't have a cat. & at last inspection I got a thumbs-up & big grin after the emissions test - make of that what you will.