Mazda 3 - Parasitic Drain
 

Hi all, this is my first time posting... never needed to before! I have been fighting with this car for weeks and I am ready to throw in the towel. I will try and summarize what I have done and experienced. I would greatly appreciate any support or suggestions... this thing is killing me.

I have a 2009 Mazda 3 Hatch. It is completely stock in every way. I stopped driving the car for the snowy month of December waiting for snow tires to come in. It was my wife's DD until then with no issues. Upon getting the tires, I went to move the car to install tires and battery was dead. I jumped it with my truck and carried on. I checked out the battery (which was old) and it was frozen solid. I swapped it with a battery from one of my summer cars and the Mazda started fine. Then within 24-48 hours it would be dead again. This carried on for a week or 2 while I tried to figure it out.

So, I performed a current draw test and with everything as normal with the key out, and all lights off; I was seeing about 150-220 mA draw. I opened up the main fuse box and pulled all the fuses with no real improvement. I also disconnected the alternator and there was no change. When I open the door, even with the lights off, there is a moment where it will jump up a bit, and then drops again once the door is closed, likely dash lights, etc. I then traced it back to the bolted down fuse labeled BTN. I reviewed the wiring schematics for the car to determine that the BTN fuse runs all the power locks, windows, marker lights, brake lights, horn, etc etc. The interior lights and radio are on a different fuse. The BTN fuse then feeds into the interior fuse box located in the pass. footwell. I pulled each fuse for the interior fuse box one by one and there was no change. I then pulled out every damn fuse at the same time, and still no change. So then I unplugged the entire interior fuse panel at the large connectors feeding into it, and finally the drain stopped.

What I have determined is that there is no fused electronic device on the entire car that is causing this drain. It is always possible that there is a worn or damaged wire that is rubbing somewhere between the BTN fuse and the interior panel, but i would expect if this were true, that the current would be higher, and that I would have popped the BTN fuse. What I was hoping to know is if there is any other possible source of power. For example, even with all the fuses out, I can still see the little blinky light for the ignition lock... so the security device must still have power directly from the battery. Just to be safe, I swapped the battery with one from my other other summer car, and there was no change.
Adding to this paradigm is that a (guessing) 40Ah battery with a 200mA drain should take about 8 days to drain. Assuming the car needs at least 50% capacity, it should be good for 4 days. Meanwhile, I worked on the car and changed the battery Saturday, and it started fine Sunday morning. On Monday morning, it was so dead that my wife said the key fob wouldnt unlock the door. So it seems to be intermittent as well.

If I just walk away for a few minutes, it appears that the current draw is settling down around 150 mA... still too high, but stable. That is with all of the interior fuses pulled, and all of the main panel fuses pulled... and 100% of that drain is coming from the BTN line.

Any thought, please let me know. Thanks for your time. It is greatly appreciated.

How are you measuring the drain?
Have you locked the car with the remote before testing?
How long are you measuring for?

Not locking your car will speed up depletion of the battery. Its a very big problem in the later Mazda's.

Which fuse box are you talking about draining the battery?

The interior fuse box is also the BCM - Body Control Module. This is basically a modern relay box.

Anything that had a relay in its circuit in older cars is now controlled thru the BCM.

That’s good to know. The interior fuse box located in the passenger footwell is fed by the main fuse called BTN, which is located in the fuse box under the hood, which basically comes directly from the battery. When I start disconnecting the main terminal blocks to the interior fuse box, the current draw will drop to 0. Like I mentioned, all the fuses are pulled out of it, and it is still drawing 150mA.So my opinion, is that there is either some electrical device pulling power that isn’t fused, OR, the fuse box itself has a short or fault internally.If it is indeed filled with electronic components and relays like you said, this makes sense. Im thinking my best bet might be to call the local wrecker and see if I can swap out the entire fuse box… this would at least rule that out. I will try and attached a picture of what the fuse box looks like so that we are all on the same page. As for keeping the car locked, I cannot argue that locking the car may change the power consumption, but we have always left the car unlocked while not in use, and never had an issue. So it would suggest that this isn’t the direct cause of my drain.Though I will try and test the drain again with the car locked, just to see what happens.Thanks a lot for your help.
https://cimg8.ibsrv.net/gimg/www.maz...d31f6d4fe9.jpg

That is the BCM.

Ive heard of other people having power drain issues from the BCM before.

If you do replace it, make sure its from exactly the same car as yours,
Same year,
Same engine
Same gearbox
Same seats
Same accessories / specs,
Same same shape
etc etc.

Yes, I did read that they had to be the same. Luckily I have no bells or whistles, and manual transmission. I'll call up the yard today and see what he has. Sounds like I may be on the right track though. Thanks for your help on this.
if I can get a replacement I'll let you know how it goes.
cheers.

So I dropped in at the yard and found the closest thing to my Mazda... it was an 06 Automatic, otherwise very close. After digging out the 3 foot of snow from beside the door, I pulled out the BCM unit.
I installed the new unit in the car, everything seemed to work. However.... still 140mA drain coming off the battery. When I unplug the green power block from the BCM, the drain goes away....
So either it is normal to have 140mA of draw all the time, or there is something else going on with an always live circuit.
I did take readings with the car locked and unlocked and there was no change at all.

Any other ideas? If not, Im thinking I may just wire a relay into the key so that the BCM loses power every time I take the key out... not sure what else to do...

Thanks.

You do need to wait 10 - 15 minutes after locking the vehicle for the whole system to go to sleep.

Drain should be less than 0.06amps

OK, so I took your advice. With the new BCM installed and everything as normal, fuses in, etc, I locked the car and walked away from it for 30 minutes or so with the ammeter left hooked up.
After the 30 minutes, the current reading was 0.01. Perfect! If I took the ammeter off, and put it back on, it would stay around 0.01. It wasnt until I opened the door that it woke the computer up again.
So the actual root cause of this issue could either be a door that wasnt closing before, not allowing the computer to sleep. (there was no door open light on the dash), or the BCM itself was faulty and wouldnt go to sleep.
I will continue to drive the car and hopefully everything is figured out.
The only issues I appear to have now, is the keyless entry doesnt work, but the power locks do. And there is a check engine light on the dash. I will run codes, but I suspect it has something to do with using the BCM out of a different car. I can live with that for now.
Anyways, fingers crossed that all is now well. grim_reaper, your help is much appreciated... I may otherwise still be chasing my tail without your guidance.

Cheers.

I think I spoke too soon.... I went out this morning to check the codes, because the check engine light came on after swapping the BCM. There were 3 codes for the heating circuit. I tried to start the car and it was dead, wouldn't turn over.
I left the key in the ON position while I was trying to connect to the OBDII. After about a minute and a half, I heard a sound that was like a servo resetting, like a brief electric motor controlling something. I turned the key and she started right up! Not sure what the sound I heard was, but sounds like something that would effect the starting logic... dare I say something to do with the heating system??
Ill do some more troubleshooting today... hope to find something simple.

Getting a BCM from a auto may not be a good idea.

What where the codes you got?

Running the codes, it turned out to be 3 of them, all for high, low, and no voltage to the O2 sensor and heat circuit. Initially I assumed heat circuit to be cabin heat, and not the O2 heater, hence my comment above, which I now realize to be out of context, because I didn't say which codes I got!
I don't think this is at all related to my issues, im sure the O2 sensor wouldn't cause a no start condition... or am I wrong?
My wife said the engine light had been coming on and off over the past few months... so may be an ongoing thing. She doesn't tell me these things :s
After having the brief issue with it failing to start, I then drove it about an hour and a half yesterday, starting it 6 times or so without any issues. My wife is leaving for work in about 10 minutes, and I am waiting for her to tell me if she was able to start it up or not.

So far it appears that the only thing impacted by swapping the BCM was the remote locks. Everything else functions as normal.... thankfully.

Wife just updated me saying car is no-start. {ugh}
Im willing to bet at this point that it is not the battery... I don't think she took the time to wait for a couple minutes and see if the whirring clickie noise occurred allowing the car to start... the saga continues... at least I know what Ill be doing after work.

***

Got home from work, turned the key, everything turns on, but wont crank. I thought maybe it could be related to the starter relay. I accidentally pulled out the main relay instead of the starter. I pulled it out while the key was ON. When I put it back in, there was that {whirrrr click} sound that I had heard before. I assume something like the throttle body resetting. Turned the key and it started right up, did it 3 times in a row. I think I will pick up a couple of relays and swap them out just to be safe. I dont think it could be much else, unless pulling the main relay caused something else to happen, but that doesn't make a whole lot of sense.
Hopefully that does it. Oddly, by battery WAS going dead before, so that parasitic drain was still a thing...

And finally.... I think this explains my current no start issues:

Recall in the works for Main Relay for Mazda3 - Mazda3 Forums : The #1 Mazda 3 Forum

In case the link doesnt work, there is a "recall" for the MAIN relay which freezes in very cold temps. (welcome to Canada). They also mention the ignition lock light blinking rapidly on the dash when you try to start it. This also happened to me. Makes perfect sense now. Next time it doesnt work, Ill tell my wife to tap it a few times and should be good to go. Will order a new one nonetheless.

Never gets cold here.

If it drops into single digits overnite in winter on the thermometer we are in trouble. 35°c yesterday.

Must be nice, it was -14 C here last night! But I bet the snowmobiling sucks in your area!!
I pulled out the relay and gave it to my wife. I said "here is the key to your car". She kept it inside overnight and in the morning she installed it and car started right up... {sigh of relief}
Again, I appreciate your help with this.

J.

Parasitic drain
 

This sounds similar to my problem. My 05 SP23 has a 220ma draw. When I locked the door it goes to 300ma. I waited up to an hour , but it never went to sleep. I unlocked the doors and after the interior light went to sleep it went back to 200ma. I started working on something else and noticed about 30 minutes later it went to sleep @ 50ma. One solution is to leave unlocked. It does have an aftermarket alarm, but haven’t used the remote for a while. I tried unplugging the alarm, but could not get amp draw to go down.

Hello All!

My box panel (BCM) causes battery draining problems, so I have to replace it.
My panel's code BS3E-66-730G

On the net I can only find BS3E-66-730D
Can I order it? Or it wont work?

Thank you for your reply!
Bence

Stumped on Battery Drain Source
 

I have a 2013 Mazda 3 with a parasitic battery drain. Before the drain started, the Bose system radio started to turn on and off by itself. A few weeks after that started, the battery started draining overnight. I had a radio shop look at the radio, and they told me the radio was bad, and was the cause of the battery drain. They disconnected the radio and the drain seemed to disappear...but it resurfaced a week later. This time, it would take 3-4 days for the battery to die instead of overnight. So, I took it in to an automotive engine shop that does electronic work. They pulled all fuses and narrowed it down to one circuit, then to one wire in the circuit located under the dash. When they disconnect that wire, the drain stops...but they don't know what the wire connects to because everything operates properly on the car with that wire disconnected! They're now thinking that the offending wire may run to something on the car that controls something that doesn't exist like an option that was never installed when the car was built...but they aren't sure.

They gave me two options for what they could do. The first, which is what they recommend, is to disconnect the problem wire and take the car for a thorough drive to see if everything operates properly on the car. That would sort of a solution to the battery drain. The other option is to remove the entire harness containing the problem wire and chase it to its source. The second option would be VERY expensive to the tune of $1500 or more. They also said that, when new fuses were installed for the radio and it was reconnected, it still didn't work, so the radio does seem to be bad but doesn't seem to be related to the problem with the mystery wire/controller they found. Does anyone here have any advice?

Hello to you. I had the same problem. Needed to change my battery 3 times. I finnally took my car to a Mazda dealer (could not locate the parasit current) to Fix it. It took them a lot time and work and money [$300) to find the cause. They said the radio was defective but there was no way to fix it. They also said some research within Mazda service notes were mentionning this particular (and apparently rare) problem.

so I am seaching for a similar radio for Mazda... to change it by myself.

Denis from Canada

Mystery Parasitic Drain
 

DenisThis whole adventure started when the radio started to go bad - turning on and off all by itself. What's interesting is that, with the radio completely disconnected, a drain was still present. When the 'mystery' wire was disconnected and the radio re-connected, the drain was gone, and the radio remained dead. Perhaps a short originating in the radio shorted out something else in the harness that contains the mystery wire. In any case, I appreciate your comment about what your Mazda dealer said about there being no way to fix the radio. We had already bought, but not yet installed, an aftermarket unit from Crutchfield but were thinking of sending the stock radio to Mazda to repair before installing the unit we got from Crutchfield. Given your comment, we'll probably just have the Crutchfield unit installed. After that, I'll have the mystery wire re-connected and seen f the drain returns. If it does, we'll just disconnect the mystery wire for good.

I know from the technicien that he needed to wait some time after disconnecting a wire before testing again for a current leak. I am actually seaching for a similar radio to install by myself. It may have to go to Mazda to get activated with a code (i will see at this time). But one thing is for sure, if I improve the same problem with my car (dead battery), I will clame my money back if they didn’t identify the problem correctly. Please let me know what happen on your side...

😉

Mystery Battery Drain
 

Looking for battery drain requires pulling fuses until the fuse controlling the offending circuit is identified. HOWEVER, each time a fuse is pulled, the car needs to go 'to sleep' COMPLETELY before a drain can be isolated. That's because various controllers stay 'awake' after the power is off - sometimes an hour or so - before they go to sleep and no longer create a drain on the battery. For the car to be completely 'asleep' where no controller or sensor is on and using power, EVERYTHING needs to be asleep. Open doors or even an open hood can keep various sensors 'awake' and creating a power draw.

Wow, thank you for the information...

2009 Mazda 5
 

Oct 2020 Dead Battery. Nov 2020 replaced battery, then that went dead (Dec 2020). Dec 2020 took it to Mazda they said battery was bad and the BCM was bad. Returned battery to Sam's and got a replacement, paid Mazda to replace BCM (Jan 2021). Worked for about 2-3 weeks and then dead (Feb 2021). (Feb 2021) Brought back to Mazda to look for original battery drain fault. They have had car 40 days.

So I don't really need the car right now, but assuming they cannot fix it... how do I get rid of car with parasitic drain? Who would buy it?

UPDATE: April 2022 (Not 2021). Fixed, no more issues.

Mazda finally came back and said it was the alternator and they changed it. After about 2-3 weeks the battery died again... When Sam's club checked it they said it had a bad cell (same fault as before). I decided the parasitic drain just was and I could not do anything about it and it was killing batteries. I put in a new battery and installed a kill switch for about 6 months with no issues.

I do not use the kill switch now. Here is what I think was wrong... I had a brand new battery when they replaced the BCM, but the bad alternator killed that new battery. When I took it back in to Mazda I assumed the battery was just drained and not destroyed... they replaced the alternator, but the battery was destroyed by then so it appeared the new alternator did not fix it. When I put in a new battery after I changed the alternator everything worked. I have no issues now.

I'm guessing the alternator showed up as good on their machine just like mine because it was charging... but it was the ultimately the alternator that was bad.

So it took roughly about 15 months for me to get from original fault back to normal.

UPDATE: July 2022. Really Fixed , no more issues.

I think the new battery kept it from dying for awhile, but ultimately it died again. I put a battery kill switch on the negative post and set off to look for someone to install a kill switch inside the cab. Took to an audio/alarm guy who wanted to see if he could fix it first before he put in the kill switch. He thought without ever touching or looking at it that it was a Bluetooth Module. He disconnected the BT and there are no more issues. I'm guessing I did not need an alternator. 31 months from fault to fix.

Ignore the terms below as I'm going to build some search terms for others.

2009 Mazda parasitic battery drain fixed
2009 Mazda5 parasitic battery drain fixed
2009 Mazda3 parasitic battery drain fixed
2009 Mazda parasitic battery drain Bluetooth Module
2009 Mazda5 parasitic battery drain Bluetooth Module
2009 Mazda3 parasitic battery drain Bluetooth Module

I have the exact same issue as you. 200 mA draw with doors locked and only 50 mA when unlocked. Just wondering if you ever figured it out?

2006 Mazda 3 Hatch - Battery Drain Issue
 

Thanks everyone for this great info. I'm having the very same issue and have checked every circuit. .213 A draw , battery dead in 3 days, 2nd new battery. Did anyone ever find the culprit?

Thanks in advance.

2008 CX9, Same story
 

I'd like to know what, if anything, has been identified as the culprit as well.

Had the same bizarre radio issues and ever since it was replaced with a Kenwood radio from Cruchfield, 3 days and dead.

It was odd though. The Crutchfield guys, who are awesome btw, could not get this new radio on with the harness.

We had to run a wire elsewhere to get it hot. Then, and this is good, it turns on and everything is wonderful... once. Then the radio turns on normally when turning the vehicle's ignition on, but no sound. Replaced the amp, no dice. So to make it work, I have to reset the radio or remove the negative on the battery after each drive, which we do. The good news is that this keeps the battery charged and makes the radio work at the same time. Of course, it's a pain and we shouldn't have to do that.

Has anyone figured this madness out?

I just went through all this with my son's 2008 Mazda 3 GT. No crank, no start when the temperature was below -10C (Saskatchewan). The idiots at two different Mazda dealer told me that wasn't a thing after 2006. No recall, no TSB. Long story short, I replaced the ignition relay (not the main), starts fine.
UPDATE: replaced both main and ignition relays as the other one needed to be too. There is also a TSB to splice in a new starter wire connection right at the starter because it corrodes. We had to do this too as he was still having issues in the 30C heat of summer. Since replacing relays and this splice, no issues in over a year. A total of $75 that you can easily do yourself. 99% of mechanics and the idiot dealers will NOT find this. The incompetence is staggering.

I carefully measured the current on each fuse for a 2014 Mazda 3 GT. It was simply a manual trunk light left on (which has a little black switch to the left side of the light), which during the day you would not notice it - drawing about 3.5A! (almost nobody knows this light is even there..) The battery thereafter can be weak. I shut off all room fuse currents and so far so good. I went with a AGM (Absorptive Glass Matt) battery as they can be safely drained to zero even in negative temperatures and come back. Drain a lead-acid battery once (especially with all the sketchy 'recycling' going on) at any temperature below -5 and it's base slightly swells and that's it - go buy another battery.

Some tips:

• Make sure the wifes phone usb is not kinked and or drawing current from the USB charger ports.
• Make sure the center console is closed properly.
• Check the trunk light there is a manual switch for it.
• To reset the radio hold the two buttons left and right of the home button plus the volume control down for about 20 seoncds
• To reset the power windows all the way down and hold it down for 3 seconds all the way up and hold it for 3 seconds. After the power windows will come back
• To reset the computer spin the wheel all the way to the left and then all the way to the right.

If you are completely unable to find it (aka rubbing wire in harness almost impossible to find) [this] will fix it.
433 Mhz Remote Control Switch will allow you to enable the fuse from remote with a FOB right before you drive it. Just make sure it is rated to the amperage of the fuse (aka 15A etc) Simple remove your fuse and insert push the contacts for the remote control switch. Bag it and it can sit snugly inside your main fuse compartments.

I had the same problem and I just replaced the entire starter assembly. You need about 3 extensions out to 16" plus a swivel and a deep socket 14mm (1/2 drive you have to crank it) and your ratchet will sit over by your wheel well - but it will perfectly align to the ackward bolt on the starter and come right out.

​​​​​​

jdschwass, I am having the exact same problems you described on my 2007 3GT. Did you ever find out exactly what was causing the parasitic draw on yours? I can trace mine to the BCM as well, and also when removing the Large green connector, the draw goes away completely (is about 250-200ma). I also have issues starting in cold temperatures so I appreciate the discussion on this, but there is still that draw that is killing batteries. Thanks!