2016 CX-5 Battery drain

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.
 
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2019 CX-5 GTR
I dont have an immediate suggestion other than to pull fuses one at a time until the buzz or humm stops.. then you at least know where to continue to journey to.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
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Plano, Texas, USA
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.
Is the battery still the Panasonic battery from factory? If it’s, just get a new battery. Interstate Group 35 battery at Costco for $79 is the best value (if you have one near by).
 
It's too darn cold out to trouble shoot today and since my covid test came back negative I will bring it down to work where its warm and try to make a video of the noise. Stay tuned!
 
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2014 mazda cx-5 touring FWD
How long does this noise persist. It's normal to hear a buzz/humming sound for less than a minute after shutdown. I forget what the cause is, but it was a brief topic on this forum a long time ago.
 
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2014 mazda cx-5 touring FWD
What @yrwei52 above said regarding replacing original battery. If it's that cold and original battery, it may let you sitting somewhere you don't want to be. You may just have 2 separate issues here being a weak battery and a normal noise.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
My 16.5 Sport always has a lingering noise. I figured fuel pump or something.

It also happens if I just cycle the ignition button thru ACC - ON - OFF without starting the engine.