p04020 then p0054

[sprkplg89]

Hi, new to forum. have a 08 gp. had p04020 code changed rear 02 sensor, code went away for approx. 100 miles, new code of p0054 . any ideas?? car does lack power at low rpms to mid. gas mileage down to 22 avg. replacement 02 sensor was a cheap one on ebay supposed to be a bosch. don't want to replace cat unless necessary. thanks in advance.

[BillBoost37]

Your issue isn't an o2 sensor, it's a bad cat.

[SgtMarshal]

bosch o2 sensor don't work well with these cars. get an ac delco next time