2021 Western Star 4900 - DD15 - Constant Fan Engagement

My 2021 4900 is having an issue where the cooling fan never turns off. As soon as the air pressure builds, the fan engages and stays on regardless of engine temperature or AC status. It's dragging my MPG down to 4.5. I've checked the coolant temp sensor through the dash and it reads normal (180-195F). The AC high-pressure switch isn't triggered. I'm thinking it's a solenoid or a wiring issue where the fan is losing its 'off' signal.