I'm in the process of replacing my stock one-wire o2 sensor with a this heated unit, per Dave W's recommendation. It's installed and wired in, but I haven't run it yet. (In the process of also replacing some oil cooler lines). Should the unit get hot around the base? I've got it wired so it gets 12v with ignition on, but I'm not feeling any heat around the base of the sensor or the exhaust pipe. I tested it by leaving ignition on for a couple minutes, but I didn't notice any temp change at all just by touch. I did test voltage and ground at the sensor connector - everything seems good. Normal behavior or is there a problem?