In this video we have a look at a customers '17 Subaru Legacy that has had a long history of the battery always being dead. She's been dealing with it for 2 years now and wants it fixed.
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Hey there viewers, welcome back to the Sou! Main Auto Channel got a 2017 Subaru it's Legacy I think it's a 25. It doesn't have a label so I don't know what it is. it's big and uh, the lady uh has been having problems with this thing with the battery going dead for a couple of years. Uh so it started it back in the year 2020.

That's when everything bad started. but that's when this thing started going through battery. So she's gone through a couple batteries is my understanding. And the car used to be a daily.

it's only got about 58,000 miles on it right now, but then it got to the point where the car would sit like uh, you know instead of driving every day she was only driving it. you know, twice a week and every time she'd go to get in it the battery was dead. uh, someone else in the family has it now or daughter or something like that and uh, the car is often dead and like I say they've gone through the swaps of the batteries and stuff and she says she has to drive it every single day now because if it sits for 2 days, it's you know DOA uh so that's it. That's all.

I know uh I do know there's an after Market remote start as there often is on these on the key fop looking on the inside. Car looks nice, super clean, everything looks stock. No aftermarket radio. Don't see any other funny business right off.

so that's all I know Uh, it's been sitting for about 2 minutes at this point before we do anything invasive. Uh, we're going to just throw a current clamp around the negative battery. We're going to see what the current draw is um, as we typically do uh with parasitic draw, uh, concerns. and then we're going to look in service info because you guys remember the last Subaru that we did had some really good info in service info which often times these cars or manufacturers don't when it comes to ghost voltage.

Uh, I don't remember what Subaru called. They had a pretty specific name for it. Um, dark current? That's what it was. dark current Darkness Uh, that's what Subaru called it and they were very specific on how long the car had to sit to time out, which the last Subaru video we did that had a bad radio.

That car only had to sit for like a minute. something like that and everything shut off. We were able to find that one really quickly. Uh, if I remember right though the guy didn't fix that, he elected to just leave the fuse out and live without a radio.

So I don't know what we're going to find here, but that's a process we're going to use and want you guys come along. Minor change of plans. We're going to send the current through the meter. Uh, this Cable's a little too big.

it's a double cable I can't get it in my current clamp right now. The car is par, shut off obviously, and the doors are locked. So if we do this wrong, we're going to get an alarm on a Subaru So plamp that baby on there. We want to get it to where it locks on All right.

So we should have current passing through our meter providing the fuse is good when we put it away. last. uh, we're going to go to grafting meter. we'll go amps internal.
now. this can handle up to 20 amps internal. I Think no 10 10 amps internal. Well, that's not a very big Big Draw My Guy Let's get some kind of cruising across the screen here for you, but you can see we're drawn well close to 100 milliamps.

Oh, that's interesting. It's kind of acting like it's creeping up there from when I very first hooked it up. Okay, there's 60. Now it's about a 60 milliamp draw.

Interesting, not excessively high. I'll put it on a 200 milliamp scale. I'll put some time on the screen here, see if we see any anomalies. Yeah, now we're down to 30 33 milliamps.

That's interesting. That's really pretty insignificant. Certainly would not kill the battery overnight, so that's kind of bizarre. If there's a date coat on this battery then might be under the cover.

What kind of interesting? I'm going to let this go over some time because see I can see it ramping up again, but you know we could still be in in the shutdown process of this. So it's kind of bizarre. Um, like I said I'm I'm put 5 minutes on the screen. we might drag out the Pico here so we can see more current over time.

All right. Well, we'll let her sit. I'm going to like I said I'm going to look in service data and we'll come back and check this out in a few minutes. So I think I'm starting to see a bit of a pattern here.

It's only been about 8 minutes and every 3 seconds, you know we're going to have this small hump here. Okay, we'll call it the little small current draw that is the blinking red light. The security light inside it blinks every 3 seconds. These other spikes here every 1 second.

approximately I don't know what they are could be perfectly normal. Um, but like I say this lower lower hump that we get. That's every time that little LED on the Dash turns on for security and then it seems to be about every minute something turns on and runs us up to about 90 to 100 milliamps and we'll see that. of course we'll see this current draw on top of whatever this is that happens right here.

So some something is happening where our one 1 second pulses if you will become a little bit longer, they stay on a little little longer whatever it is. And then of course we still have our LED our security LED blinking every 3 seconds. We can get that out of the mumbo jumbo and then we come here and like I say it holds around. you know 9200 milliamps and whatever this is turns back off so to speak or goes away rather after about a minute or so.

but it happens just about every minute. Pretty consistent I was seeing it there when I had more time on the screen and that's it's. going to shut off here and then like I say we still have our blinking security light. We lose our 1 second pulses that we were getting but we still have our security light blinking and then in a little bit it'll drop back down to you know, the 30 milliamps.
So it goes back to our 30 milliamps. got some funny business there and then it goes back to you know, quote unquote normal where we have a current draw every 1 second and then our security light blinking. So I think there is definitely something wrong. uh I still have yet to look at service data because I get sidetracked hey squirrel and uh, you know, start looking at this and and I think we have have enough data to go on here to say like yeah, this probably isn't normal whether it's a module waking up or doing something I really don't know.

it's pretty low current. so I don't know if we're going to end up making our tests every minute while it's broking. If we go, you know what? we go down the fuse and and find out where this current draw is going. Uh, but I I don't think that these pulses every one second I don't I don't believe that's normal I might have said I think it's normal but I don't believe it is.

I've a lot of current draw testing on cars and you don't see stuff like that. You'll see the lights kicking on and off the LEDs But here we are going into another one minute cycle. So and like I say those pulses that were every 1 second now become bigger and that's our LED light kicking on our security light. There's another one there just on the edge.

Here's another one on that back. Edge So like I say every 3 seconds we're going to see this LED light kicking on there. So yeah, Anyhow, so that's what it does. It repeats it over and over over and over again.

So just so you guys know, that's kind of where I'm at and now I'm going to go back and do what I told you I was going to originally do look at some service data think I might have found it folks. So I got to wait about a minute for this thing to kick on whatever it's doing and then as that's happening I'm measuring voltage drop across each fuse for the you know the 30 or 40 seconds that it that it does it. So right there it's drawing current and look at my meter point. 3 molts across this fuse right here now.

I'll stay kind of paned back as soon as the current draw goes away. so doesn't our voltage drop across that fuse? So let's just wait for it here. it doesn't last very long. It took me a while I started of course way over here on the left hand side and finally made it over there.

so we're down to 2 molts of voltage drop across the fuse. still has 64 milliamps of current draw. wait for it to go away and there it is. We're back to quote unquote normal and we have no current draw across fuse.

So that made it tricky because I had to I could only test it while it was broken. Um so anyways let's see what that fuse runs and see where it goes get be able to. So that was kind of a tricky one. Let's see that is the third row and so third row and it's a very top fuse and that says you guys probably can't see it but it says DCM Delta Charlie Mike 7 12 amp.
So let's look on a power distribution and see what that runs. Yeah, so right now it's doing it again. Well I guess before we do that, let's just go like this. Let's grab these from the previous job that we didn't take care of.

Oh come on, you stick pots There we go. Let's pull that out. Let's just yank the fuse. Boom problem Sol baby you just got to pull your fuse and now all we have is our blinky light every 3 seconds for security.

So I'm going to set that fuse right there and that looks like a normal current draw pattern. So the last Subaru we did I think was drawing around 30 milliamps. um so we can we can put some time on the screen. we'll put uh, we'll just go like 3 minutes we'll say and we'll just let this continue to go.

It's going to look a little wobbly over there because like I say the LED that's blinking on the inside change the time basis so it looks a little better because this the problem was happening every every one minute. So let me go see what this fuse runs. and we do that by looking in a a power distribution diagram and it'll tell us everything that runs off that fuse. So I found it right here.

Oops, where's my point? I Guess this is all we got for a pointer. Big scraper. uh, fuse number 9, 7 and2 amp only feeds one thing. Hooray for us! Uh, data communication module and I have no idea what that is or what it does.

Here's how we're fixing this one folks. BCM Fuse Taped batter's reinstalled. Put that back in there and I'll tell you what I figured out. Good news and bad news folks.

The DCM or the Telematics Data Control Communication module get mixed up here has to do with Subaru's uh Starlink I guess they call it uh so it seems to be their version of GM's OnStar uh satellite. uh you got like your SOS button up here and this information button and and stuff like that. It is a subscription service that the customer has to pay for. I'll fast forward and skip a whole bunch of stuff.

It took a while to figure out what all this module does for everything, but that's mostly it. Um, the radio will still function the the XM radio will still function. She'll still be able to hook to uh, the audio here with her. uh Bluetooth uh the best I can figure out that should all still function I've left the fuse out because I got a hold of Subaru because I wanted to see.

well how much does this module cost? You know it appears that something funky is gone with it. Let's just start figuring things out. see if they're available soon as I called Subaru The guy says not a chance, young fella. He says they've been on a forever back order.

They make them out of un itanium and you can't get them great. Subaru has a service boltin on it because apparently this is an issue with people trying to swap and use ones and that's a big no. no. Um, so they have a bolletin issued to their dealers saying do not Swap this out or take this out for any reason and put in one from a different car and this that and the other thing and if you need to obtain a new one, here's the process to go through and we'll fast forward from that point I asked the guy at Subaru I said so if these are on back order what are you know? What are you guys seeing coming in the shop? Almost every single case is parasitic draw So it's kind of interesting.
um that I've never run across this before. Uh, but the fact that he knew right off hand also that this data communication module was a common source for a battery draw and he can't get them. Uh, he says you can put one on order. he says they've been getting them Trinkle in you know here and there every once in a while you know, been on back order for a couple years and then get one every you know month or so but it's as a I guess you're put on the the list.

So checked with this lady. uh, gave her the options. you know we can get it, we can wait, we can go a little further or we can leave the fuse out of it and everything works on your car and you're not paying for Starlink service anyways and she says, yeah, that's what she wants to do is just leave the fuse out of it and enjoy the car and not fix a feature that she doesn't even use. so we're not going to go any further.

That's that if you want to go further with yours I Guess you got to I Was looking at service data, the whole Center stack here comes out. uh, the navigation unit and all that stuff and the heater and the modules back in there. but there is a process to replacing it and installing it. uh, other than just you know, plugging it in and calling a day.

So so that's it. That's where we're at. That's a lot of Jibber jabbering uh for that, but kind of a neat uh battery draw. So maybe if you're working on a Subaru and you see that same type of current draw that's coming and going now, skip all the BS yank the fuse out uh for that DCM and see if it takes care of it and this will save you some time.

But uh, I'm sure there's some Subaru guys in the comment that maybe can elaborate on this as far as what the Telematics Data Communication module does on and Beyond just the SOS button and stuff like that I Didn't look into it any further, but what I will look at is your comment in the comment section, questions, comments, the insty the Facebook and just remember viewers if I can do it, you can do it. Thanks for watching.

98 thoughts on “Subaru legacy – battery keeps going dead for the last 2 years”
  1. Avataaar/Circle Created with python_avatars Daddyoh says:

    This is the only way Subaru owners would know any thing about this problem. Great work Eric. The voice of honesty.

  2. Avataaar/Circle Created with python_avatars Kevin. I says:

    My neighbor had the exact same problem. Did the same thing and pulled the fuse for her and the car is working fine. She was so greatfull for me fixing it, said I saved her thousands of dollars because she was ready to trade the car in. The dealership wanted to replace battery and alternator for big $$$. What a rip off, suspect they knew what the problem was all along.

  3. Avataaar/Circle Created with python_avatars bcreason says:

    Twice my wife’s Forrester has had the battery go completely dead over night.
    It’s a pain in the ass. Have to use the key to open the door and pop the hood. I have a couple of those small lithium boosters. They can’t start a car if the battery is completely dead. So they were almost useless. I couldn’t boost it from our other car because it’s parked in the narrow one car garage. I can’t roll it out because it has electric parking brakes that I can’t disengage because there’s no electricity.
    Luckily I had a little 1 amp lab supply that I used to charge the battery very slowly. But it would get to point where there was enough power for the alarm to go off and start honking the horn and flashing the lights using up the little charge I managed to get.
    Eventually between the supply and the two boosters I managed to get enough power to disengage the electric parking brake and push it out of the garage so I could boost it with the other car.
    I now bought an expensive car starter battery charger and of course now it hasn’t happened since.

  4. Avataaar/Circle Created with python_avatars Félix Bouchard says:

    Great video, the owner does need ti get away from this fram filter…

  5. Avataaar/Circle Created with python_avatars Carl Drexler says:

    My 17 Outback has the battery dead seemingly every 6 months since I got it in 2021. 2 of the 3 times I was at my parents so I had a charger handy. The first time the battery died I was in the city… called a Co worker. I was thinking every time I left the triggered the rear hatch light to stay on accidentally while unloading. I was about to pull off the switch to not catch it accidentally but maybe I'll look for the tdm fuse… now.

  6. Avataaar/Circle Created with python_avatars ToughAncientSpark says:

    Btw, I have a parasitic draw on my 2016 Outback.
    I pulled the DCM fuse in the fuse panel and the draw went from .74 microamps down to .64 microamps. Not a big change like in the video.
    Something else is causing the draw and will have to investigate further when I have the time.

  7. Avataaar/Circle Created with python_avatars 38911bytefree says:

    Module probably has a cellphone module, it is like a cellphone without a screen so you can send and receive data. Seems like module is turning on to send data or to register to the network. Probably the suscription to the cellphone provided is out and it can no longer register to the network which put its sw into a certain loop. Changing this crap probably requires matching the IMEI / phone number into some Subaru telemetry system ???. Other module could freak if the IMEI from the new module does not match wuth the one they have stored somewhere else ?.

  8. Avataaar/Circle Created with python_avatars Tom Jacka says:

    i dont think ill be buying a subaru or a ram

  9. Avataaar/Circle Created with python_avatars scott McIntosh says:

    Dr O solved another one genius !!! You are the very best !!!

  10. Avataaar/Circle Created with python_avatars Phil N says:

    My old Honda CRV got them same thing so I have to install the power cut off switch to turn it off ever day to reserve battery.

  11. Avataaar/Circle Created with python_avatars Dana Jorgensen says:

    I have a 1994 Honda Accord that does this periodically (bought it new, thank you very much). Turns out, the problem is a short in the driver side door control console. In the cold months, frost forms that shorts a couple of the switches. Tracking down automotive electrical gremlins can be a nightmare. Especially when the car predates ODB2 ports. I only got a clue when I went out one frosty morning to find the mirror adjusting itself.

  12. Avataaar/Circle Created with python_avatars coyote Kelly says:

    2020 was definitely a decline for us. FJB

  13. Avataaar/Circle Created with python_avatars Jim says:

    Amen 2020 is when the parasites took over. God bless and overcome my man.

  14. Avataaar/Circle Created with python_avatars Ronald Bryant says:

    This problem must have irritated enough owners that some owners have filed a lawsuit against Subaru.

    Subaru owners have reported experiencing premature parasitic battery drain in vehicles equipped with Starlink in-vehicle technology. The defect presents itself when the equipped data communications module (DCM) attempts to communicate with 3G cellular networks.

    Subaru 3G Battery Drain Lawsuit | Wexler Boley & Elgersma LLP

  15. Avataaar/Circle Created with python_avatars Dawood says:

    Since starlink is no longer supported, an I just unplug my fuse?

  16. Avataaar/Circle Created with python_avatars Lex Luthor says:

    Had the same problem with this issue: Did a power draw test and ended up being the blue tooth module. I just ripped it out behind the glove box and threw it away. Never had this problem again.

  17. Avataaar/Circle Created with python_avatars Benjamin Brower says:

    Electronics repair man might be able to fix that circuit board in the module

  18. Avataaar/Circle Created with python_avatars Mike Johnson says:

    Same thing with the Hummers… pull fuse.

  19. Avataaar/Circle Created with python_avatars joseph espinoza says:

    Nice job .? So how do you or how much diag.time to charge .

  20. Avataaar/Circle Created with python_avatars Thomas Hart says:

    I am surprised that we consider a 100ma draw for a minute, every other minute is sufficient to make a car unstartable. For a 600 CCA battery (82ah) a battery should last for 820 hours, not 48. Of course that presupposes some reserve capacity, but I'd think that there would be plenty left after 48 hours.

  21. Avataaar/Circle Created with python_avatars robert sr bell says:

    You are one smart guy good job agan .

  22. Avataaar/Circle Created with python_avatars Briana Croft says:

    Why you quit using snap on scanner ?

  23. Avataaar/Circle Created with python_avatars Richard Gill says:


  24. Avataaar/Circle Created with python_avatars Keith Reilly says:

    Have a 96 F150 that’s gonna parasitic draw that if I let it sit for three days, the battery is completely dead

  25. Avataaar/Circle Created with python_avatars splice247 says:

    Just fyi, newer Hondas with telematics can also have this issue, had many DOA causing a draw, there's a tab I believe that. So if you see one out of warranty now you know

  26. Avataaar/Circle Created with python_avatars KJV Dust says:

    Eric, can you give me a promo code for the swag store? Christmas shopping.

  27. Avataaar/Circle Created with python_avatars Henry Alligood says:

    Thanks for not being a hack. I just watched a video of a guy in Pennsylvania bypassing a fuse/relay and patting himself on the back because the car started. I'm an electrical engineer and I tried to advise him that he is going to have unpredictable results if the lady activates her ABS since the circuit is now in parallel with another circuit. Not to mention the dealer will never touch the car again when they see the creativity bestowed upon it. I was thinking…Eric O would not be his buddy…..

  28. Avataaar/Circle Created with python_avatars Starcrunch72 says:

    I have an 09 Hyundai Elantra Touring wagon that had a parasitic draw. The clue was a warm spot on the roof between the windshield and the sunroof. Opened up the roof center "console" and found a dealer installed GPS unit that was tied to a Hands-free button and mic/speaker. Removed=fixed. Too many gimmicks…

  29. Avataaar/Circle Created with python_avatars Malcolm Duncan says:

    I got a DCM once…it was Don't Come Monday…as the boss closed up the business!

  30. Avataaar/Circle Created with python_avatars jet knight says:

    One's first thought would be an alternator but it's not always that case the best way know if it's an alternator is to bench test it for better results.. a normal working alternator should have a draw of 13.5 to14.5 but if it's 12.5 or less very weak..

  31. Avataaar/Circle Created with python_avatars wazza33racer says:

    Why does the Starlink/DCM need to draw power with the vehicle off? There is no reason why it cant be a key acc/run position, relay driven power supply. I had a similar problem with a BMW……the climate control was drawing power with the key off……what on earth for? If I want the climate control to keep the blower motor running with the engine off, It could just be running with the key on Accessory.

  32. Avataaar/Circle Created with python_avatars Phillip Bailey says:

    Excellent diagnosis!

  33. Avataaar/Circle Created with python_avatars Ed H. says:

    You done the right thing! Thanks for making these videos. great job as always! Ed Hicks

  34. Avataaar/Circle Created with python_avatars KH L says:

    But even a continuous 100ma current should not flat out the battery in 3 days. In fact the average current draw should be around 65ma(half time 40ma, half time 90ma), it would take about a month to drain full charged 45ah battery at this amp

  35. Avataaar/Circle Created with python_avatars Murray M says:

    It's got the big two five. I think Eric O and his family are the poster for the hard working American family. I think his wealth of tools and knowledge are the key. There's many out there with the skills but without the knowledge or tools which are pricey. Dang. Maybe it's already happening I'm not sure. But there should be some kind of loan available. Get these guys a shop. Work on older cars for people having hard times. Do videos on them so the customer can see their car come together. With great videos like these. They can learn.

  36. Avataaar/Circle Created with python_avatars Frankie Lemonjello says:

    Stupid thing's trying to 'handshake' to an extinct system.
    Call all you want, no one's ever going to pick up.

  37. Avataaar/Circle Created with python_avatars Mohammed KH says:

    cant understand something 100 mA is like 1 amp after 10 hours and thats not considered a high draw at all if that car sets for 7 days it should be able to start unless it have other problems like bad starter or something

  38. Avataaar/Circle Created with python_avatars Sean Toothill says:

    2020…that's when "everything bad started" You couldn't be more right my friend

  39. Avataaar/Circle Created with python_avatars mark walsh says:

    Well if you’re not using it you might as well chop it off 😂😂

  40. Avataaar/Circle Created with python_avatars William Holcombe says:

    I have the same problem with a Nissan 2008

  41. Avataaar/Circle Created with python_avatars Joe BP says:

    I don’t own a Subaru. The car I own you probably haven’t worked on in 10 years😂, but I love your videos, very knowledgeable and honest mechanic here. Watching from South Jersey, take care man!

  42. Avataaar/Circle Created with python_avatars Aran Haydar says:

    I diagnosed an Altima last year that had the same issue,

  43. Avataaar/Circle Created with python_avatars Mike Page says:

    Nice technique!

  44. Avataaar/Circle Created with python_avatars Mike TeeVeeDub says:

    Today I learned that pulling a fuse actually cures a no-start condition. Modern vehicles are just too dang complicated, filled with doodads no self-respecting driver really needs other than bragging points.

  45. Avataaar/Circle Created with python_avatars Wutheck says:

    Pulled my DCM fuse last year. All my battery issues went away.

  46. Avataaar/Circle Created with python_avatars Johnny M. Rodriguez R says:

    Great find as usual!

  47. Avataaar/Circle Created with python_avatars Ken Lendener says:

    Check the glove compartment light, not going out.