Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › O-2 Heater Monitor Won't Set. › Reply To: O-2 Heater Monitor Won't Set. October 19, 2020 at 5:11 pm #986769 Lady DIParticipant Can the O-2 heater “circuit” be tested with a quality scanner. I want to make sure there is no electrical issue. Again no CEL present.