o2 sensor
 

so the engine lite comes on check engine. code is oxygen sensor one bank one you put in a bottle of fuel inj cleaner it goes off for six months. mechanic says its not the sensor why does this occur. any thoughs

What is the EXACT code number?

O2 sensor
 

Ok, we get all five of the engine codes I listed. Four of the point to the four O2 sensor, bank 1, sensors 1&2, as well as bank 2, sensor 1&2. Hard to believe that all four sensor went bad at the same time.
We have add injector cleaner, twice. Maybe we need to add more over a long time period.

If it were only that easy.

There is no quick permanent fix with anything that comes in a bottle.
Someone is going to need to check the entire system for possible contamination since it keeps coming back.