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.

 

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

 

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?