0509 again please hlep

Hello all,

I have cel on and the code is 0509 the same o2 sensor that I replaced 7 month ago.


I have reset the ecu but on the highway when I force it to pass other cars on a slope for instance , the light comes back on.

I am not sure changing that o2 sensor will resolve the problem.
Please help.


Thank You

....
Please help. Thank You

Car model? Miles? Last maintenance? Tested sensors? Self diag?

Start from basic maintenance.