It's been a while now new presence has emerged with this code. Is it the sensor the sole culprit or low quality gas also produced the code because the last trip we went to a mountain area where good gas is not available so we filled our fronty 05 with smuggled cheap gas. From there on, P0138 was thrown. And I wish to get some tips from our members who ran into this before and successfully solved the problem. To me, I think I should start with a cleaner diluted with the gas to help clean the injectors. And if the problem persists, I'll go straight to the o2 sensor by swapping btw them. Any ideas from our community will be appreciated. From Cambodia.