O2 sensor oscillating between 0.1 and 0.2v

Hi guys,

Hope every body are ok here.

I had to help my step father on his car to change spark plug. He wanna do it.
No DTC, but I put my scan tool to check if every thing was ok and I found O2 sensor precat doing strange behavour.
O2 sensor oscillating with very good sinusoid but only in lean state, around 0,1v and 0,2v. 
So I was convised that O2 was bad, and as part changer, I changed the 02 sensor with a new one... and... values are still around 0,1v and 0,2v.
As there is no DTC... I try to understand :
- is it a wideband O2 sensor ? fiat 500 1.2 69 cv 4 cylinder 2014. I really think it's a narrowband sensor
- Dirty injector?
- Ground issue?

Do you have any advices ?

Best Regards,
ludo

Hey Ludo! Unfortunately, we don't get the 1.2L engine here in the states. But I'm gonna hope the 1.4L is close enough.

Based on my experience with Fiat and Fiat-era Jeeps, I would be surprised if it wasn't a wideband sensor. How many wires did the replacement sensor have? If it was four, it was probably a narrow band. If it was six, it was a wideband. 

Do you recall what the fuel trims were before and after the sensor replacement? 

Hi Tyler,

I forget to mention, it's a 4 wires sensor. For fuel trim, both with old and new o2 are same. Ltft around +4 in several rpm. Stft has a strange behavior for me but i really don't know fiat. Before starting, stft is -100. After, sometime is going to -100 like when injectors are not delivering fuel after good acceleration. Without this, stft is moving around -6, + 10 at idle.
I do not notice anything wrong during drive test. Spark plug and O2 was little bit white but very little... so for me seems to be correct and not so lean but i have doubt with this o2 values... sometime, i dont know if im trying to find problem where no problem is here in fact.

Hi all,
I received today after 1 month and half due to long travel from US to France, ScannerDanner book and I found how to troubleshoot this issue.
Seems to be bias probably with ground. Will finish to read and have look on SD video, but already I know with this site in what direction to go. Great. Will let u know. Regards.