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Old 12-15-2020, 09:19 PM   #1
Swagon_Wagon
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Default SBF No.8 fuse parasitic battery draw + Alarm

Car details:
2006 LGT.
About 160,000 miles.
Minimal aftermarket wiring and No recent changes to the wiring when this problem occurred.
Aftermarket wiring includes stereo related items, horns, That's about it.

Hello, I've got quite the hard parasitic drain to find. I've been chasing this ghost for well over 6 months now. I don't drive the car every day so it hasn't been too big of an inconvenience to have to unplug the battery but it's finally gotten on my nerves enough that it's time to solve it. My first round of troubleshooting involved pulling fuses while monitoring drain current and I must have missed it my first time a few months ago but this time around I noticed that my steady-state drain rate of around 0.3 amps reduced down to 0.18 amps when I pulled this fuse. Upon a search, I found another user on this form had a similar issue also relating to the same fuse number in his 05 wrx which I'm assuming shares a very similar wiring harnesses to my '06 LGT.

Symptoms-----
-When the problem first occurred it was first notice with a weird issue. That issue is that whenever I lock the car, The alarm system would go off instantaneously and I could turn off the alarm by locking it again. The alarm system is the factory Subaru alarm system that came with the car. I could leave the car sit for around 2 to 4 days before I couldn't start the car again so I resorted to unplugging the battery whenever I was going to let the car sit for more than a day.

-Recently I was driving along and my speedometer started to erratically cycle to zero and back to reading normally and by the end of the day it was stuck at zero and the trip odometer reads "er sd".
I bring up the odometer issue since I understand that those are related to the ABS system in a way and upon reading the other users' topic about his drain I know that this fuse may be related to the ABS system.
The issue with the alarm going off whenever I lock the car is still present although sometimes for a short period of time the alarm doesn't go off. It is not clear at this time if the alarm is related to the short but the timing of the two problems makes me think that they might be related. I also have not located a fuse that is related to the alarm system by name. I'm assuming there's a locally mounted fuse near the alarm system or maybe it is also supplied by SBF-8.

Here is the link to the post I'm referring to from the other user.
https://forums.nasioc.com/forums/sho....php?t=2390095


I suppose I'm making this post to gather information and troubleshooting ideas as well as a source for an FSM(EDIT: found one) If anyone happens to know of one.

I suppose I should start with diving into the DTC codes related to the odometer issue but I didn't think to read them before taking the car apart for some other items I'm working on and I didn't have a check engine light yet so it didn't cross my mind to read them, woops. The speedo only recently stopped working, unclear if this is related to the drain.
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Last edited by Swagon_Wagon; 12-19-2020 at 10:15 PM.
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Old 12-15-2020, 11:20 PM   #2
Swagon_Wagon
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Ok more info. There is a black box located under the steer column that has 3 plugs going into it that I'm having a hard time identifying the plug numbers on.

Dome light off, door light bulb removed so that current is not visible, trunk light confirmed off.
Only visible items that should be drawing current, the flashing security light(locked or unlocked)

DATA:

225ma with SBF8, and all 3 connecters plugged on the is box I've yet to identify.

If I pull SBF-8 out. security light stops flashing and current drops to ~110ma and then 5-10 seconds later drops to 10ma. This black box as far as I can tell relates to the keyless entry, the door open light, seatbelt chime speaker is inside it as well. If I unplug all of its plugs the current with sbf-8 installed is 78ma.

I know this all pretty useless data but recording it allows me to reference later on in this process.
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Old 12-19-2020, 11:36 AM   #3
Cougar4
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My data shows that fuse SBF-8 is the fuse for the alternator charging lead. The main alternator lead should have battery voltage on it at all times but if you remove SBF-8 then the main lead should not have power on it. Check the current drain while the main alternator lead is disconnected from the alternator and things are in the sleep mode. There may be a problem inside the alternator that is causing the excessive current drain. I think normal current should be less than 28ma.

For the speedo issue there may be a connection problem to the speed sensor or to power.
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Old 12-19-2020, 07:37 PM   #4
Swagon_Wagon
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I'm still learning how to navigate this FSM but I'm not seeing what you are saying at all. In drawing P-SUP-02(FSM page WI-16(PDF page 5280)) I'm tracing SBF-8 off the page via (F) to P-SUP-05 on FSM page WI-19 where it branches out into tons of other circuits. Am i looking at the right section?

Also, their is no VSS on this car, that's and older Subaru thing, I think the 4th gen legacy got rid of that. Only got 2 sensors on my trans, neutral and reverse. I was very sad to see this change in design.

The black box I believe is the BIU now. I'll have to start de pinning the wires one by one on that to trace the drain current. A tiny, sensitive clamp on ampmeter would be pretty great right about now..

Last edited by Swagon_Wagon; 12-19-2020 at 08:13 PM.
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Old 12-19-2020, 09:17 PM   #5
Swagon_Wagon
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QuickSilver

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Ok update. The only branch fuse off SBF-8 that is hot while the car is off in fuse #7 which supplies loads listed as FB-17 and FB-18 which are noted as:

-TPM control module(tire pressure? My car dont have that)
-Impact sensor?(for the alarm? that could be it since my alarm goes off the moment I lock the car. Where is that sensor located assuming its for the alarm and not the SRS airbag sensors)
-Combination meter(My speed stopped working. Would be sweet if all these issues were realted)
-And the Body integrated unit.

Last edited by Swagon_Wagon; 12-19-2020 at 10:11 PM.
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Old 12-20-2020, 01:09 PM   #6
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My data seems to be a lot different from yours. Which year service manual and car model are you using?

Check the voltage on the main alternator lead while the car is off. You should have power there. Then remove fuse SBF-8 and check the power again. Does it go away?
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Old 12-22-2020, 02:26 PM   #7
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Remove relay/fuse panel from under hood pop plastic cover off lower end of the junction box. Look for your power feed wire you'll see a nut should be 10mm tighten it I'd bet it's loose. Mine was common issue on many cars. Also make sure corresponding pins are making good tension to your fuse that's causing the issue. A loose connection and terminal pin tension issue will cause a power draw. Along with a faulty relay..


I personally would unplug all of the connectors on that junction box and pry the terminal pins using a pic or small flat head or thing needle nose pliers to add tension to the terminals so they grasp the pins tightly. These are major issues in today's automobiles. And cause major issues and shorts in computers. Ever pull a fuse or relay and notice discoloration on a pin? Yeah that's a bad thing and a sign of connection lose in the terminal pin itself. If and or not a over drawn current possibly caused by a issue with the motor on said circuit. Could be drawing to much amperage for the wiring or relay used. Or the relay could be over rated for the circuit itself. Vise versa fuse as well.

Last edited by spoolinsti05; 12-22-2020 at 02:37 PM.
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Old 12-22-2020, 02:40 PM   #8
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Also wouldn't hurt to invest in an amp clamp. Or learn how to use a voltmeter to check such.
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Old 12-22-2020, 05:51 PM   #9
Swagon_Wagon
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QuickSilver

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Quote:
Originally Posted by Cougar4 View Post
My data seems to be a lot different from yours. Which year service manual and car model are you using?

Check the voltage on the main alternator lead while the car is off. You should have power there. Then remove fuse SBF-8 and check the power again. Does it go away?
Here is the link to the FSM I downloaded.
https://mega.nz/file/JVgkXaTb#yR-5Jg...5uPcyYi7YDAzyQ

So far everything I have traced follows what I'm seeing in that manual. 2006 legacy manual. Covers all models. Mine is the Turbo model with 5 speed.(Legacy GT Spec.B)

And for current measurement I'm using a Fluke 77 which I trust. I was just saying it would be nice to have a small range(like 0-30) Clampmeter for this as mine is a 1000amp clamp meter which is useless below 1 amp.
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Old 12-22-2020, 05:59 PM   #10
Swagon_Wagon
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Quote:
Originally Posted by spoolinsti05 View Post
Also wouldn't hurt to invest in an amp clamp. Or learn how to use a voltmeter to check such.
I have been using doing that with my FLuke77. How do you think I've been measuring current down the the 1ma level
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Old 12-23-2020, 12:07 AM   #11
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Quote:
Originally Posted by Swagon_Wagon View Post
I have been using doing that with my FLuke77. How do you think I've been measuring current down the the 1ma level
Must've read over that before posting. Are you letting the car go into sleep mode before testing? Also how are you testing? By removing the neg terminal and running the meter in series to cable and battery post?
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Old 12-23-2020, 12:18 AM   #12
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Also pop out the sbf 8 fuse and I'm pretty sure you should only have power to one pole not both. If you have power to both poles on fuse you have a bad capacitor inside the module. It could be sending power back to power. In such case you won't get a current flow.

Voltage and ground are the basics current, amperage and resistance are the huge game changers.

It's like trying to put two magnets together. They push apart from one another.
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Old 12-23-2020, 06:00 PM   #13
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Having a Fluke to use for a meter is great. Here is a link for just one of the many meters that will work to measure low current DC.

https://www.amazon.com/dp/B07G84XDWH...NsaWNrPXRydWU=

Have you performed my previous mentioned test yet? Remove fuse SBF-8 and then see if there is power on the main output lead of the alternator? If not then do that. If you have no power there when the fuse is removed then disconnect the main output lead from the alternator, keep the wire end isolated, and then check your current draw. If the current has dropped then the trouble is inside the alternator.

Last edited by Cougar4; 12-23-2020 at 06:16 PM.
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Old 12-26-2020, 10:18 PM   #14
Swagon_Wagon
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Quote:
Originally Posted by spoolinsti05 View Post
Must've read over that before posting. Are you letting the car go into sleep mode before testing? Also how are you testing? By removing the neg terminal and running the meter in series to cable and battery post?
How long does sleep mode take?

yes, typically I run my meter inline with the battery, the + terminal to be exact. (shouldn't matter where I measure + or - terminal I'm assuming. )

sometimes I move the meter to a fuse terminal to measure the current at a particular branch.
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Old 12-26-2020, 10:33 PM   #15
Swagon_Wagon
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2006 SpecB #41
QuickSilver

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Quote:
Originally Posted by Cougar4 View Post
Having a Fluke to use for a meter is great. Here is a link for just one of the many meters that will work to measure low current DC.

https://www.amazon.com/dp/B07G84XDWH...NsaWNrPXRydWU=

Have you performed my previous mentioned test yet? Remove fuse SBF-8 and then see if there is power on the main output lead of the alternator? If not then do that. If you have no power there when the fuse is removed then disconnect the main output lead from the alternator, keep the wire end isolated, and then check your current draw. If the current has dropped then the trouble is inside the alternator.
I have 12 volts at the main lug on the alternator with or without SBF-8. SBF-8 is not for the alternator. The MAIN SBF(120amp) is the alternator fuse. The 3 wire plug on the back of the alternator gets its 12volts from Fuse #16(7.5a) which feeds power to pin#2 on connector f26(the 3 plug connector on the alternator)

Cougar4, I know you are trying to help but i really think you are looking at the wrong diagrams SBF-8 has nothing to do with my alternator on this car haha. Did you download the FSM from the link I posted?

I really need to find the security system impact sensor. that could be my golden ticket.
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Old 12-26-2020, 10:36 PM   #16
Swagon_Wagon
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QuickSilver

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Quote:
Originally Posted by spoolinsti05 View Post
Also pop out the sbf 8 fuse and I'm pretty sure you should only have power to one pole not both. If you have power to both poles on fuse you have a bad capacitor inside the module. It could be sending power back to power. In such case you won't get a current flow.

Voltage and ground are the basics current, amperage and resistance are the huge game changers.

It's like trying to put two magnets together. They push apart from one another.
I only have 12 volts(battery voltage) on the left pin of the SBF-8 fuse pins. as I should.
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Old 12-26-2020, 10:44 PM   #17
Swagon_Wagon
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QuickSilver

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Quote:
Originally Posted by spoolinsti05 View Post
Remove relay/fuse panel from under hood pop plastic cover off lower end of the junction box. Look for your power feed wire you'll see a nut should be 10mm tighten it I'd bet it's loose. Mine was common issue on many cars. Also make sure corresponding pins are making good tension to your fuse that's causing the issue. A loose connection and terminal pin tension issue will cause a power draw. Along with a faulty relay..


I personally would unplug all of the connectors on that junction box and pry the terminal pins using a pic or small flat head or thing needle nose pliers to add tension to the terminals so they grasp the pins tightly. These are major issues in today's automobiles. And cause major issues and shorts in computers. Ever pull a fuse or relay and notice discoloration on a pin? Yeah that's a bad thing and a sign of connection lose in the terminal pin itself. If and or not a over drawn current possibly caused by a issue with the motor on said circuit. Could be drawing to much amperage for the wiring or relay used. Or the relay could be over rated for the circuit itself. Vise versa fuse as well.
Lifted the fuse/relay board and tightened both my 10mm connectors. They turned a bit but not enought for me to think they were loose.

I also unplugged and replugged all the connectors under there while monitoring current. As excepted, my current draw disappeared when I pull connecter B144 which is where SBF-8 leaves the main fusebox on PIN #3(Green)
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Old 12-26-2020, 10:47 PM   #18
Swagon_Wagon
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So after trying all of that, I'm back to the circuits that branch from SBF-8.... Refer back to post #5
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Old 12-26-2020, 10:59 PM   #19
Swagon_Wagon
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Found my Impact sensor below the passenger seat. I Unplugged it and no change, further testing required on that sensor. Assuming if that sensor is disconnected that alarm will sound when locked? Does anyone want to test that theory?

Okay, I have the cabin fuse panel half pulled out. A 200ma draw turns into 10ma when I pull connector b52 out of the back of the cabin fuse box. according to the diagrams, the only pin on B52 that is powered by FUSE 7(which is an always live fuse in line with SBF-8) is Pin #19(B52) but when I put my meter inline with that circuit(B52 unplugged but using the meter to connect pin 19 back in) I only read 41ma....smh (Pin19 B52 is for the BIU which I have yet to look at diagrams for...

I also Pulled all the blue relays next to the cabin fuse panel with no change in a amp draw as well, to rule out the 2 relays that are also on SBF-8(but those relays only get triggered on by the Ignition switch so that was expected)

I'm kinda stuck now and overwhelmed... reading up about the BIU and it does alot of stuff, not sure if that something you can just swap a new one in.

Last edited by Swagon_Wagon; 12-27-2020 at 12:10 AM.
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Old 12-28-2020, 03:07 PM   #20
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It sounds like you may have isolated the trouble to the BIU. As far as I know there isn't any programming needed for that module but I could be mistaken. The BIU is tied to a number of circuits and I suppose it may be possible that the BIU may be okay and something it is tied to has a problem.
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Old 12-28-2020, 03:52 PM   #21
Swagon_Wagon
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Tomorrow my local yank a part opens and I'll be heading there for parts for sure.
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Old 12-29-2020, 10:45 PM   #22
Swagon_Wagon
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Well the pick yard is closed. But I put the car back together ish and my speedo works again... weird. Pause this issue untill i find an open yard.
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Old 12-30-2020, 09:13 AM   #23
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Are you absolutely sure your car doesnít have TPMS?

Some of the pre 2008 cars got it before it was mandated. If there is a module under the drivers seat. Iíve seen several of these get corrosion from water and take down the speedo. There may also be a connector just covered in green corrosion fuzz.

https://legacygt.com/forums/showthre...?amp;p=1174400
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Old 12-30-2020, 11:44 AM   #24
spoolinsti05
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Quote:
Originally Posted by Swagon_Wagon View Post
How long does sleep mode take?

yes, typically I run my meter inline with the battery, the + terminal to be exact. (shouldn't matter where I measure + or - terminal I'm assuming. )

sometimes I move the meter to a fuse terminal to measure the current at a particular branch.

I believe it takes up to 30 minutes. You also need to tape the door switch shut or jump it. With it open you could wake up the systems and that will cause a draw.

You can check pos or neg side either way. You can also set it to voltage reading and get same results. By running one leed to ground and other to positive wire that's causing the issue. It's most likely something shorted in the board circuitry on a module. These modules can get hot and they lack cooling fans. Most electronics and capacitors have a 105c rating which is good. But over prolonged time may fail as that rating will drop from heating and cooling.

Some say you can even hit the brake to drain the systems. But I prefer linking the battery terminals as I know it will reach all the systems in the car as they're all linked to main power and ground.

If you disconnect both pos and neg battery terminals and touch them together it will discharge all the control systems capacitors. To put everything in sleep mode instantly. Even when discounting the battery the capacitors will still hold a charge as they're designed to. And if you're testing a circuit with a capacitor inline you will get a reading until it discharges.

Does this car have an anti-theft system? They constantly draw power.

Last edited by spoolinsti05; 12-30-2020 at 12:03 PM.
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Old 01-03-2021, 05:27 PM   #25
Swagon_Wagon
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So I found that finding this exact BIU module in the local yards is not easy. But a quick eBay search for this part number, 88281AG28A. Yeild some results. Not all the numbers on the label match but that and some others do. Anyone know which numbers are important? Is 88281AG28A the official subaru part number?
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