2020 Subaru Outback - Battery Keeps Dying / Parasitic Draw

Question

I'm on my third battery in two years. If I drive the car every day it's fine, but if it sits for more than 36 hours, it won't even crank. The dealer says the battery is 'fine' and the alternator is charging at 14.2V.

I've checked that all the interior lights are off. I suspect there's a parasitic draw somewhere but I'm not sure where to start looking on such a new car with so many electronics. Is there a common module that stays awake?

TireGuyTrevor · Accepted Answer

✅ Confirmed fix: The DCM (Data Communications Module) for the Starlink system was failing to go into 'sleep mode' after the car was turned off, pulling about 180mA constantly. Pulled the DCM fuse as a test and the draw dropped to 15mA. Had the dealer replace the DCM and perform a firmware update. Problem solved.

HondaHankk · Answer

Subaru has a TSB for the Battery Sensor on the negative terminal. If it's faulty, the alternator won't charge the battery to full capacity during short trips, leading to a deep discharge state over time.

ShopForemanShane · Answer

Check the rear tailgate latch. Sometimes it doesn't fully seat the 'closed' switch even when the door is physically shut. This keeps the CAN bus awake because it thinks a door is open, draining the battery in about 20 hours.

2020 Subaru Outback - Battery Keeps Dying / Parasitic Draw

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