I have been throwing a code for quite awhile but I have to get my car inspected this week and I am throwing the P0031 code front O2 sensor heating circuit low. is this the sensor in the uppipe? I have a 03 wrx sedan with catless turboback helix exhaust, I also have the resistor fix on the uppipe sensor. any help would be greatly appreciated, thanks oh yeah I only run 93 octane and higher, never 87

 

if its the heater circuit in the 02 sensor that means it has gone bad. Replacing the 02 sensor is the only fix. Its bank one, sensor one..IIRC that is the one in before the uppipe