CEL On Code P0031 & P0420

Check Engine Light is on. Code P0031 & P0420. Just replaced front upstream o2 sensor, but CEL is still on. Cars a 05 WRX A/T & all stock. What could be the problem?

P0031: H02S Heater Control Curcuit Low (Bank 1 Sensor)
P0420: Catalyst System Effciency Below Threshold (Bank 1)

 

I had a P0031 a few months back and ended up replacing the Bank 1 Sensor 1 (by passenger front wheel) and also had coil pack 2 failure. Not sure if they were related at all but that solved my issues

 

Yes, OEM O2 Sensor as I heard Subarus are picky.

 

Battery is new and replaced just a month ago. Haven't checked the grounds between the sensor and ECU yet since it's raining.

 

I had an o2 cel come on multiple times in the gfs outback. Found that the car had iirc bosch and not denso sensors and apparently there was enough of a difference to matter. I swapped the rear out have have been good since.

 

I used a Denso one as well and worked for me