Good day , We have a 2016 CX5 with 62k on it. Just this week I have noticed the battery is discharging over night ...every night. I have removed it charged it and it is holding a good charge (15 V+) with no drain down over night . Once installed vehicle starts no problem ,but after engine is shut off there is a low hum or buzz coming from the area around the air flow sensor leading me to believe there is a solenoid or switch that is stuck on? draining the batt over night . Its cold here -20C the car is plugged in and also has batt blanket on, tested plugs and everything is getting power. There is no dealer here and local shop rate is 175$ hr and being so close to the season I would rather spend on the kids any help or suggestions would be greatly appreciated.