O2 Sensor INfo

Great idea. I bought last year used, it has 160k on the motor and seems to be running fine but it probably could use a tune up. I immediately had the transfer case and transmission serviced as I was hauling a 20 foot camper around all summer and wanted to be nice to the transmission. I have noticed that my MPH though is getting worse, I am down to about 16 MPH in the city, which I think is a few MPH lower than it should be. Will take to a shop, get a tune up and let them check the cat and sensors too.

 

I usually replace the downstream or secondary O2 when I replace a cat. That O2 is the monitor of the cat, the upstream deals with how rich/lean the vehicle is running. On today's modern vehicles for me a "major" tune up I check the MAF the upstream O2s to see if they are still working well i.e. not sluggish. Air filter, fuel filter (if equiped). stuff like that

 

If it's been 200 miles and you haven't seen the code/cel come back, just keep rolling. Yea the cat may be degrading but it's not like it's going to get more expensive if you wait until the cel is more permanent.
There may have been a once in a while fluke in the strategy that determines a cat failure (p0420/430). The pcm can get fooled from time to time.

 

Thank you that helps. Wasn't sure if I could cause damage by not addressing it immediately. So far, everything seems to be running fine. Will keep an eye on it and report back

 

Here is the update on the error code. Fortunately I have a friend/client who happens to have every known auto gadget invented and was more than happy to diagnose for me. He tested the entire system with his computer and it turns out is was bank 2, sensor 2 failure. Cats were still in normal range. The odd part is that the sensor did report the issue back but hasn't thrown a code since the original issue. So, as for right now leaving everything alone but more than likely if this shows up again, will just replace sensor. I am very glad it was not a CAT! Thank you to everyone for all the great info and help. Really made understanding what was going on a lot easier for me to understand. Happy trails (Now if I can only manage not to slip on the snow last week and have to take a drainage ditch out to avoid a school bus... $1,500 worth of body damage, in the shop now... Passanger side rocker panel and bottom of door took a hit. Amazing thing though, this truck was incredibly leaned over in the ditch and I have no idea how it didn't roll and I ended driving it out with the help of a tow strap pulling on the side to keep from rolling... So all in all a very good day minus the $1,500).

 

Not a plug for the site below - just a reality check about cat converters.

https://www.discountconverter.com/why_catalytic_converters_fail/index.cfm

 

Curious as to how he came to that conclusion.

 

That is really good info the other thing is CATs degrade overtime as well so one can go bad just due to degradation. Usually there is another cause for the failure like someone riding around with the car missfiring for months if it was a vehicle with less miles.

 

Will and try and get you the actual details and results as to how he came to that conclusion. His computer that he connected to the OBDII was able to measure the test results while running the engine at specific RPM's and then comparing to what the results are supposed to be. I know, very lame answer but don't have the actual tech knowledge to give to you, but will find out.

 

In the almost almost 20 yrs of experience I have seen maybe 1 that had that code and the O2 sensor was the fault and not the CAT. I have had that code along with other codes for missfire, lean, etc. The cat code was secondary to the other issues, but when it is the lone code then in my experience which is extensive like I said maybe one O2 was bad the rest were all CATs. Not saying he isn't right.

 

Oh no, I sure hope is right too. Really don't want to have to replace the Cat's - that looks very expensive. Will update you if anything changes, knocking on wood (literally right now). I will ask him what led him to his conclusion and get some real information that maybe will hope make more sense of this. Hoping I am not wrong either in what he is telling me. ugh.

 

The cat code is THE ABSOLUTE LAST CODE THE MANUFACTURE WANTS TO EVER SEE. Manufacturers have to warranty the cat for 8yrs/80k. The pcm has multiple strategies for testing the cat, you're not going to be able to duplicate that kind of testing with a scan tool or a code reader.

 

Exactly. Plus having all the tools and gadgets doesn't make you a great tech or know what you are doing. I have met many so called techs that couldn't diagnose their way out of a wet paper sack but they had all the tools and equipment. You can't properly test an CAT monitor O2 sensor just looking at PID data over a scan tool.