Gave the engine a bath and it was running like crap, threw an 02 sensor code. Eventually got it cleared up and is finally running well.   

I have the ODBLinkMX+ reader and it gives all kinds of run time information, speed, fuel, consumption and most important for this discussion, 02 sensor voltage.  The MX+ is telling me through the runtime that O2 sensor 1 is ranging from 0 to 0.97 volts, but sensor 2 is 0.0 volts all the time. This is not throwing a code.

I assumed sensor 2 is the rear one so I disconnected it and immediately the ECU threw a code, "Sensor 2, no activity" Reconnected the sensor, clear the code and its running fine. 

I am going to assume that that sensor is sending information, but given it is always zero, should I be replacing this 02 Sensor?   The engine seems to be running well but I hear the voltage should be constantly ranging between 0 and 0.99 volts. 

It is end of life and I am on borrowed time?

A low voltage 02 sensor indicates too lean, is the ecu taking this and then giving more fuel than required?

Regards,
Colin

[2015 Z Force 800 53/Trail EPS]

One thing to remember is that...at least on the previous machines, they first numbered the banks or cylinders when that engine was in a CForce and that was the other direction then in the SxSs so Bank#1 is the one closest to the muffler or tail lights in the SxS and Bank 2 is behind the seats. And that both O2 sensors should be reading about the same. I have no idea why the one shows nothing and doesn't generate a error code...but check the connectors as they do get water in them. Some even crack.

Interesting, I unplugged the rear one again and again the MX+ said o2 Sensor 2 but when I check P-codes in the service manual they say what you said.  Bank 1 sensor. 

I think I will just just replace it.  I can get them up here in Canuckistan for $70 cdn.  We don't have anyone offering anywhere near a good deal as O'Reilly's.  Even through out the US, they are by far the best price. 

Better that than running it to lean or too rich.

I will use this one based on another post.  https://cfmoto-forum.com/alternative-parts/2021-z950-sport-alternate-o2-sensor/


https://www.oreillyauto.com/detail/c/direct-fit/bosch-direct-fit-oxygen-sensor/b02d/15314?q=15314&pos=0

Take care and thanks for the info.

Well that was a waste of money.  Replaced the O2 sensor and it still shows zero on the obd sensor.   Anyway it runs fairly well and that is really all that matters.