Is it time for new O2 sensors

[RedEnvoyDenali]

My 5.3L Denali is approaching 170K km's (100 K miles) and i have heard the O2 sensors should be replaced at about 100K miles. Is this accurate? Should i do all 4 sensors? Are the sensors like our spark plugs and somewhat sensitive to brand? What brand seems to work best if they are sensitive? I would think that replacement should be straight forward if not a little painful on a couple of the sensors.

I like to do the preventative maintenance so that it doesn't become a panic situation. Want to thank all who chip in for their time. This site has been a godsend for the last 7 years i have had the Denali.

 

[Mooseman]

Some replace them, some don't or just wait until they fail or have poor performance. If you do replace them, just do the upstream ones as the downstream only check if the cat is working properly. And yes, ACDelco is preferred.

 

[RedEnvoyDenali]

Some replace them, some don't or just wait until they fail or have poor performance. If you do replace them, just do the upstream ones as the downstream only check if the cat is working properly. And yes, ACDelco is preferred.

Thanks Moose that is exactly what i wanted.

 

[djthumper]

Just remember it may take a lot of work to get the old one out...

 

[Mooseman]

That's "ones" with an s, he has two on the V8.

 

[Chickenhawk]

Personally, I do them every plug change (every 160,000 Km on the I6 engine) just to prevent them from seizing to the manifold. (That can cause a LOT of problems.) They are exposed to the exhaust stream every second the vehicle is running, so it just makes sense that they will deteriorate over the years.

Or, if you wanted a more scientific answer, put it on a scanner and look at the readings. You will seem them get a bit 'lazy' after a few years; not enough to light a code, but enough to affect performance. You can tell instantly if they are starting to go bad. (A good sensor will vary readings up and down from 100 mV to 900 mV many times a second.)

 

[linneje]

It is not getting the old ones out, it is getting the harnesses disconnected and then connected that is the hard job in the V8. Really tough access to the harness .....

 

[RedEnvoyDenali]

Thanks to all who replied,I will take your advice. I will start with a scan to see if i can pick up any lazy sensors then replace the upstream whether they appear good or bad. If i get a downstream that is looking lazy I think I will replace that as well. A few good swear words and lots of patience will usually get the job done. Thanks again looks like i have another project.

 

[mrrsm]

A Handy O2 Sensor Socket Wrench (Shorter and Easier to use in tight places)
http://www.autozone.com/loan-a-tools/oxygen-sensor-socket/oem-oxygen-sensor-wrench/948079_0_0/

But...this tool works so much better if the O2 Sensor base is first sprayed down with CRC-Freeze-Off:

Here is an inexpensive O2 Sensor Socket from Harbor Freight:
http://www.harborfreight.com/78-in-oxygen-sensor-socket-69022.html

 

[Chickenhawk]

Thanks to all who replied,I will take your advice. I will start with a scan to see if i can pick up any lazy sensors then replace the upstream whether they appear good or bad. If i get a downstream that is looking lazy I think I will replace that as well.

Don't worry about the downstream sensors. Their readings should be quite steady. If the downstream sensors start to vary readings as quickly as the upstream ones, it will throw a code that your cat performance is off. Replacing the downstream sensors contributes nothing to performance; they are only there to monitor cat efficiency.

 

[RedEnvoyDenali]

Don't worry about the downstream sensors. Their readings should be quite steady. If the downstream sensors start to vary readings as quickly as the upstream ones, it will throw a code that your cat performance is off. Replacing the downstream sensors contributes nothing to performance; they are only there to monitor cat efficiency.

Noted and acknowledged. I will leave these alone until codes start appearing. thanks