2016 Legacy battery parasitic drain

[Duboisly]

I have a 2016 legacy 2.5 limited. I have a battery drain / parasitic load issue. As of September 2021 I've replaced 3 batteries and about to put my 4th in. I did a drain check and on Fuse 9 under hood/main fuse box I get 0.6 amp drain then when i pull the fuse it drops to 0.06 amps. This feeds the data communication module / DCM. I haven't troubleshot it more from there.
How long does it take for the DCM to go to sleep mode?
Also has anyone changed out a DCM, how tough is it?
Per the manual it looks like you have to pair the unit to the car, can that be done by a DIY person?

 

[Retired Engineer]

Have a parasitic drain on my Mercedes, can't find it. Installed inexpensive battery disconnect on Negative pole of battery, problem solved. You may wish to use disconnect that operates from cable to dashboard. Also nice theft protection. Drawback is your DCM will need a few miles to "re-learn" tuning parameters. I can't even notice this.
If this "hard Reset" doesn't correct the present Subaru DCM, isolate it from power, and then mine is a plug-in exchange for new one. Then same "learning curve" occurs as you drive it first time, this should "pair it to the car."

Noticed you'e replaced three batteries while troubleshooting. Subarus are noted for their relatively small batteries
(possibly to reduce weight), and then of course automobile batteries are not able to be fully recharged after being fully drained. I swapped in a same Group 24 deep cycle marine battery. Wow! Huge improvement. Cost me $88
exchange for my dying "5 year" Interstate, on the way out at 3 1/2 years. You'll need to remove battery tray to accommodate deeper height of an inch or so, and don't forget to re-install black plastic heat shield. May need to buy one longer battery cable. I found an Advance Auto Parts store close to a lake, so it stocked lots of marine batteries.
Hope this helps.

 

[dmakris]

Have a parasitic drain on my Mercedes, can't find it. Installed inexpensive battery disconnect on Negative pole of battery, problem solved. You may wish to use disconnect that operates from cable to dashboard. Also nice theft protection. Drawback is your DCM will need a few miles to "re-learn" tuning parameters. I can't even notice this.
If this "hard Reset" doesn't correct the present Subaru DCM, isolate it from power, and then mine is a plug-in exchange for new one. Then same "learning curve" occurs as you drive it first time, this should "pair it to the car."

Noticed you'e replaced three batteries while troubleshooting. Subarus are noted for their relatively small batteries
(possibly to reduce weight), and then of course automobile batteries are not able to be fully recharged after being fully drained. I swapped in a same Group 24 deep cycle marine battery. Wow! Huge improvement. Cost me $88
exchange for my dying "5 year" Interstate, on the way out at 3 1/2 years. You'll need to remove battery tray to accommodate deeper height of an inch or so, and don't forget to re-install black plastic heat shield. May need to buy one longer battery cable. I found an Advance Auto Parts store close to a lake, so it stocked lots of marine batteries.
Hope this helps.

...or you could identify the root cause of the drain - I just posted diagnostic steps that worked for me under 2017 Outback battery drain topic: https://www.thesubaruforums.com/posts/65841/

 

[Duboisly]

Update: Subaru recently sent me a letter that the DCM will cause some of the same issues now that 3g is no longer available. DCM does not go into sleep mode.