I got the cat changed last year for catalytic converter P0420 error on my 2016 CRV. 6 months down the line I got the P0139 error. I changed the downstream sensor this time. 2000 miles more I again got the same P0139 error. I called Denso and they sent me a new sensor because of warranty. I called the mechanic to reinstall the downstream sensor and he says P0139 error may be because of upstream sensor also and recommending to replace upstream sensor. I am so confused this is driving me nuts!!!!!!
![How to Fix Engine Code P0139: O2 (Oxygen) Sensor Bank 1 Sensor 2 [NEW 2023]](http://i.ytimg.com/vi/Mqd7h6AU3ys/mqdefault.jpg)
![How to Fix Engine Code P0139: O2 (Oxygen) Sensor Bank 1 Sensor 2 [NEW 2023]](/img/tr.png)
![HOW to Clean O2 Sensors [For FREE]](http://i.ytimg.com/vi/tvUElYga5m8/mqdefault.jpg)
I got the cat changed last year for catalytic converter P0420 error on my 2016 CRV. 6 months down the line I got the P0139 error. I changed the downstream sensor this time. 2000 miles more I again got the same P0139 error. I called Denso and they sent me a new sensor because of warranty. I called the mechanic to reinstall the downstream sensor and he says P0139 error may be because of upstream sensor also and recommending to replace upstream sensor. I am so confused this is driving me nuts!!!!!!