Hello, I just wanted somebody's input before I go ahead and replace my o2 sensor.

I recently got one of those Ob2 readers and looked at some data.

My o2 Bank 1 Sensor 1 is at 0 at idle. The only time I see it jump higher is when I come to a complete stop. It will jump to a normal value and drop down in a split second to 0 and remain at 0.

Does this mean my P0171 is related to the bank 1 O2 sensor?


When My P0171 happened:
Somebody cut me off, so I slammed on the brakes, enough for the ABS to kick in, I revved my engine (to assert my dominance, jk), and a rotten egg/sulfuric smell came about. Then the P0171 turned on.

 

Rotten egg smell means your catalytic converter failed. That's the ONLY COMPONENT on the vehicle that can make that smell.

To determine if the O2 sensor is working you need to look for the voltage fluctuations to verify it's cycling properly. You can google something like "oxygen sensor voltage fluctuation" to see what it should look like.

You may have other components out of spec that caused the catalytic converter to fail. P0171 simply means there is a problem with bank1 running lean, there's quite a few reasons for that case. I would pull all the spark plugs and see if you have 1 wet plug, a stuck injector can dump a ton of raw fuel into the exhaust which destroys the cats but the system is actually running lean on the other 2 cylinders so it shows some crazy readings and usually a lean error code as well. Low fuel pressure, vacuum leaks, bad A/F sensor, bad MAF are typical culprits of the P0171 DTC.

 

I read through it, I understand it is supposed to fluctuate, in which case, mine does not it stays at a almost cosntant 0, sometimes it moves a little up, but does not even hit .1

I am just wondering if my Bank 1 is lean, could that be the cause of flat 0 on the O2 sensor?

 

No it will ALWAYS fluctuate if it's working properly.

 

Here is my data log:
https://imgur.com/a/4mbmeXs

Notes:

1. O2 sensor Notes

I did not include pics of Downstream O2 sensors, but the

• Bank 2 DOWNSTREAM is functioning properly (Going from .1 to .9)

Whereas

• Bank 1 DOWNSTREAM is fixed at .9

EXCEPT: I notice when I downshift (Triptronic), OCCASIONALLY Bank 1 will oscillate properly up till I come to a stop, then it will drop down to 0 and stay there...
Bank 1 F/T will slowly go up from -20 to about 10 or 20, drop down to -20 and then continue the cycle.
Bank 2 F/T is -20 at all times, but I have no code for it imo.

 

Do the logging directly from graphing mode instead of that overview widget mode. Select EVERYTHING that TorquePro lists as an O2 sensor and graph them all at once. It's possible that it's mistaking which sensors are actually the O2 sensors. There should be like 6 or 8 different O2 sensor options. Can't remember for sure.

 

Replaced O2 Sensor on Bank 1, CEL is fixed and O2 is back to normal.

In my case, it was weird that the O2 worked occasionally, but was indeed a dud.
No more P0171

 

What about the egg smell?

 

Egg smell is your catalytic converter reaching the melting point. There's definitely damage to it so it's worth removing to do a visual inspection for how big the melted spots are. Good chance one of them will need to be replaced.