Check engine light codes

[Michaelquerty]

My check engine light came on after the dealer cleared my codes and I don't have the time to drop it off since they are notoriously slow and don't have loaners. The car seems to run fine. Anything I could check myself?
The codes are
P0137 Heated O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
P2096
P219A

Thanks

 

[MrFord619]

Any mods on the car or is it stock?

 

[Michaelquerty]

It threw the codes when the car was stock, I cleared the codes and tuned it and the same codes came on. It'll go one or two drives after I reset the codes before it throws another check engine light.

 

[MrFord619]

My over the internet guess is possibly a bad O2 sensor. My brothers went on his Mazdaspeed 3 at 15000 miles so it happens. Have you noticed a MPG difference since the problem has arisen?

 

[Michaelquerty]

That's the funny thing, the car has gotten around 28 mpg before the codes started appearing and now gets the same mileage. I am tempted to just ignore it. When I first got the car almost two years ago I didn't keep the nozzle in the tank for 10 seconds and the car idled funny afterwards and threw a code, but it came off the next time I filled up correctly. At first I thought it was from filling up incorrectly again, but I keep the nozzle in for a good 15 seconds lately. I'm going to try and switch gas companies and see if that helps, I use Shell 93 octane atm.