P0028 Subaru - 2007 Subaru Impreza stock 64k miles

Question

I just got this code after my head gaskets were replaced and my head was machined. Any thoughts on what it could be?

Answer 1

if you replace the oil after the repair? if not you could start by changing the engine oil and filter, and clearing the engine code by disconnecting the car battery (30min or so) if you dont have an obd-II reader to clear the code. 

if the problem is still there the sensor might be bad if the harness is not open or shorted.