"as soon as I drove it the check engine light came on code P0137 so I went ahead and changed back sensor."
Can you clarify. Did you replace the upstream sensor with the original?

 

it was a o2 sensor purchased on ebay, the technician who changed it said he uses them all the time, should I used a oem sensor??

 

Normally OEM sensors are used to avoid problems.
Seems tech who diagnosed/repaired would be responsible for getting it right.

 

I would not use any sensor like CJ1 said except oem.

 

the tech is a friend whom I got to install the sensors, which I purchased on ebay, he did not charge me to put them on. thank you very much for your info, I will see about getting oem sensors and putting them on!!

 

For some reason, Denso has the best results and works well with the ECU.

 

The P0137 is the downstream sensor. The bad fuel mileage indicates possibly another issue. Maybe an air intake leak? However I would first sort out what sensor got replaced. I'm strictly a Denso guy and I buy them from rockauto.

Sent from my SM-J320V using Tapatalk

 

Save your money and buy the same exact sensor as OEM which is Denso off RockAuto.

 

oem sensors for those only, had many aftermarket sensors throw fault codes after installing

 

P0137 is a low voltage code from the downstream sensor. If this happened after replacing the upstream sensor, its possible the issue killed the downstream sensor completely.

After ensuring your sensors are proper denso replacements, report back.

Part numbers:

234-9052 (upstream)
234-4233 (downstream)