Hi All,
I was playing around with my Dashcommand App today and imported the data to an excel spreadsheet to examine my pre-cat O2 sensors. Attached is the voltage readout of the pre-cat sensor on driver and passenger side. Voltage seems to fluctate between 0.1 and 0.9 and then smooths, which seems to be how a O2 sensor normally functions. The horizontal axis is a timestamp, but I cannot figure out the formatting. The vertical axis is the voltage of the O2 sensors. Feel free to comment.. I wonder what other parameters would be interesting to analyze?

 

I would assume the blue is the drivers side upstream cat and the Orange is the passenger upstream cat.

If that is correct I wonder why the drivers side is much more active and I was also wondering why there is a large gap then activity again, but only on the drivers side.

I may have misunderstood...

 

Very interesting ? what kind of OBD unit are you using ? and do you get the VSC lights on after using it ??

 

Yes that's correct, the drivers side is much more active. That leads me to believe that the sensor on the passenger side is going bad. I have heard o2 sensors die a slow death sometimes and effectiveness can diminish with age; but others say o2 sensors either work or don't work. Is this evidence of slowing sensors? I will do another analysis tomorrow. I don't know that there is that flat line for both sensors.

 

It's a kiwi obd wifi device. About $20 on amazon. But you have to buy the app which is $50. No VSC lights or side effects. It just transmits engine parameters to your iphone then you can download the excel file. Will do some more pivot tables tomorrow and post for fun:-)

 

If possible do an upstream/downstream chart on each side.

You should see plenty of .1-.9vdc activity on the upstream but a more stable voltage on the downstream O2 sensor.

Then, try all four at the same time unless it makes the chart too difficult to read.

Also, what value is the time Stamp?

 

Thanks for the tips. I'm changing my post cat sensors today to address a P0161 code. Once I get a reading for all 4 sensors, I will post my analysis. I suspect that the pre-cat sensor(s) are degraded..

 

Just checked the Dashcommand user manual, and the line with more variability is the pre-cat O2 sensor voltage and the one with less variability is the post-cat O2 sensor voltage. I also read that the voltage for the post-cat sensor is supposed to be less variable since its only purpose is to measure the efficiency of the catalyst..

 

I too have that type of information as I troubleshoot my p0430 problem on my Trans Am. I am going to replace the O2 sensors this weekend to see if it clears the cat low efficiency. I believe these O2 sensors are original, making them 15 yrs old with 68k miles on them. That would be way beyond there life expectancy.

I think it is funny that I am installing Denso on my GM product!

I am running another bottle of Techron through the system and hope it cleans things up a little more.

 

I also have a thread on O2 spacers you can check out...

 

Lex, check out this video sometime...it is long but now I really understand cats and O2 sensors....