O2 sensor....

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NewGuy

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I am having a mental dilemna regarding oxygen sensors and preventative maintencance vs. wasteful spending. I have an '04 Tahoe with 166K miles. I just replaced the plugs for the 2nd time and changed the oil. I keep it well maintained as I drive it for work and put a lot of miles on it.

My question is this. At 166K miles I have never changed the Oxygen sensors. The suggested maintenance says to check/replace the O2 sensors at 100K, but here I am closer to 200K and I have never done anything with them at all.

Should I...
- Drive it until I get an error code?
- Change the pre-cat sensors now (~$100)
- Change all 4 O2 sensors (~$200)

I have heard stories where a failing O2 sensor will cause the computer to make adjustments that will make the car undriveable. I don't want to get caught 6 hours from home...in the rain...and have the O2 fail and ruin my trip.

Thoughts or suggestions?
 
Failed O2 sensor(s) may make ECU adjusting fuel/air mixture to run rich and the result is lower gas mileage and worse emission.

I would not change O2 sensor(s) until it failed. You may want to buy a basic scan tool such as Aquus 3100 for less than $100 to monitor your engine conditions, including O2 sensor(s).
 
I just changed the O2 sensore in my Saab 9-5 after 244,000 miles! Bosch claims that replacing the sensors can improve fuel efficiency, and make the job pay for itself in under 12 months. I haven't seen much MPG change in the week since I installed new sensors.

But since you know the O2 sensors can wear out, and you have 166K miles on your truck, and a failed sensor may require expensive Dealer service if it fails away from your tool box, and fresh sensors may increase your fuel efficiency, why are you delaying?
 
I would replace the pre-cat sensors. Those are the ones that can affect mpg; I wouldn't be surprised at all if you saw an increase in mpg if you replaced them. I prefer Bosch O2 sensors.
 
FWIW, I've had nothing but bad luck with Bosch sensors, particular when used with GM. I put three different ones on my '97 Monte Carlo before it would run at all, and even then it was never quite right. Had I planned on keeping the car I'd have replaced it with an OEM (probably Denso, but who knows anymore).

If you want to keep waiting, you can probably go longer. If the sensor wonks out on you, you can unplug it and keep on driving, but expect some bad fuel economy and a SES. I've done it before, it's not a big deal.
 
I would drive it until you get an error code(s), especially codes P0131, P0171, P0300, then replace O2 sensor. I just went through this on my mother in law's 02 Tahoe. IMO, there is no reason to change O2 sensors before they fail, unless you really enjoy preventive maintenance.
 
Every time I have had an O2 sensor go, it set the check engine light, and I didn't notice any performance difference from the engine, just the fuel economy got worse... Prolongued driving with a failed sensor can screw up your catalytic converter, but your CEL will be on long before that.

Drive it till the computer says there is a problem and you will be fine IMO. I have never seen a car not drivable because the 02 wasn't working...

I drive for a living like you and spend 8-10 hours in my car each day with many miles and I don't worry... My last car was at almost 300K KM (180K Miles) before one of the 4 O2's went in one of my old cars.
 
Originally Posted By: StevieC
Drive it till the computer says there is a problem and you will be fine IMO. I have never seen a car not drivable because the 02 wasn't working...


The "quality" Bosch sensor left my old car unable to idle and accelerating roughly after being installed for just a few hundred miles. Luckily I was minutes from home, and as I said, I just pulled over, reached back there, unplugged it, and it was fine to drive home.
 
That would have been because it was shorting out and causing false readings to be sent back to the ECM so the fuel mixture was off. Your ECM should of turned the sensor input off by that point or shortly thereafter and defaulted to factory values stored in the ECM and set a CEL.

Secondly... I wouldn't use a Bosch O2 if my life dependent on it... They're junk IMO and I have nothing but problems with their sensors (4 of them in 2 different vehicles)... I much prefer a Denso or NGK. All of these I have used have lasted until the scrap yard hundreds of thousands of kilometers later...
 
I know how it's supposed to work. It didn't ground short. After I got it home, I brought it to a friend and I actually watched the readings from the computer with a real scanner (not the [censored] code scanners). It was oscillating as you'd expect, but not in the correct range. I wouldn't even call it lazy, it was just wacked out. I could see why the ECM didn't just shut off the input.

Either way, moral of the story is avoid Bosch junk.
 
o2 sensors can operate in a tired(lazy) mode and not throw a code. My vehicle was feeling sluggish with no other option that stuck out. I replaced the o2 sensor and the vehicle runs normal now. I like NGK plugs and sensors for my GM vehicles. The o2 sensors are are NGK but boxed as NTK.
 
I appreciate all the good discussion on my topic. The conversation and comments in this thread are similar to the pro/con discussion I have been having with myself. The gas mileage and performance has slacked off a bit, but I was hoping that the new plugs would help. One of the things that got me to thinking about replacing the O2 sensors was that 2 or 3 of the plugs I replaced (~100K of wear) seemed to be a bit different than the other plugs. They appeared to be a bit "rich". Could this be O2 related? Getting that scanner seems like a good idea too.

I am not crazy about Bosch parts either. I use ACDelco or NGK plugs for all our vehicles. I have never used Denso parts, but they have the best reputation. Does anyone know where NGK or Denso O2 sensors can be bought? I checked AZ, AAP and O'Reillys, but no one has them on their website. Does NAPA carry NGK? I will check on NGK/Denso prices and post back tomorrow night. Bosch O2 OEM equivalents are ~$50/each, but I expect NGK or Denso to be more expensive. I might just replace the pre-cat sensors.
 
Last edited:
Originally Posted By: mstrjon32
I know how it's supposed to work. It didn't ground short. After I got it home, I brought it to a friend and I actually watched the readings from the computer with a real scanner (not the [censored] code scanners). It was oscillating as you'd expect, but not in the correct range. I wouldn't even call it lazy, it was just wacked out. I could see why the ECM didn't just shut off the input.

Either way, moral of the story is avoid Bosch junk.


This must be a rare problem, I haven't seen this on any of my vehicles... Good to know!
wink.gif
 
Originally Posted By: sciphi
Denso for GM cars. Not Bosch.


I used a Bosch direct fit sensor (pre-cat) on my Saturn. No problems at all.
 
All this nonsense about Bosch parts being poor quality is absurd!

Perhaps a few "stealth marketing" folks posting around the car sites over the past few years.?

Bosch parts are very good quality on par with Denso (did you know that Denso and Bosch work in partnership as well?)

The only thing I would say is that I would choose the OEM brand for the specific application, (eg. Bosch for VW, Audi, ect and Denso for Honda, Toyota ,ect)
 
Last edited:
Originally Posted By: The Critic
Originally Posted By: sciphi
Denso for GM cars. Not Bosch.


I used a Bosch direct fit sensor (pre-cat) on my Saturn. No problems at all.


I agree. I've used Bosch 02 sensors on several of my vehicles - 1 GM and several Fords. Never any problems with them. First time every time!

Originally Posted By: DoubleDee
o2 sensors can operate in a tired(lazy) mode and not throw a code. My vehicle was feeling sluggish with no other option that stuck out. I replaced the o2 sensor and the vehicle runs normal now.


I agree with that as well. I've had that happen. No engine codes or check engine light.

Personally I feel since 02 sensors are relatively cheap and on some vehicles very easy to change (not so easy on others) it's worth it to change ever 100K miles or so.
 
I wonder if anyone had given thoughts that perhaps there's a few variants of O2 sensors out there, not just different brands?

Quick check on wikipedia shows that there's the zirconia and titania type, and both have different operating principles, and likely different voltage characteristics. If a car comes OEM with a zirconia type O2 sensor, and is replaced with a titania type sensor, it is not surprising that the ECU will be utterly confused as the voltage range will be different. This is perhaps a real danger with the universal 3-4 wire sensors... how do we know that we are putting in the correct sensor that the OEM uses?
 
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