P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
 

I'm getting this error code and the check engine light is on:
P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

Haven't noticed any difference in performance or response. I've tried resetting the code and it comes back pretty much immediately.

Anyone else had this? Where would I find the sensor to check if all the wiring is OK? Where's best to get a replacement sensor if I need one?