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Discussion Starter · #1 ·
Hi guys,

I have problem in my fuse box under the glove box. My tail light and dashboard light goes off. When I hit under glove box sometimes light turns on. I went to the dealer and he said my BCM module has a problem and it should be changed. It cost lots of money. I checked on eBay and found similar part. But I am not sure it will work. Would you tell me if this replacement part will work?

Original: BP4K 66730 F 140604
Replacement1: BP4K 66730 G 120705
Replacement2: BP4K 66730 H 090206

Can someone tell me what is the meaning of F, G, H. Should I buy any of these replacement parts and change myself. Your advice would be helpful. Thanks
 

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I'm sure it's different revisions of the same module, BUT, I don't know how hard coded the BCM is to the PCM. That's a question for a Mazda specialist that has extensive experience in changing out those module, which ain't me.
 

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You said the lights work when you hit the module (sometimes)?
I think it's an electronic fault in the module, a contact or something similar.
Car mechanics, they don't know how to fix such a breakdown. I think it is necessary to take the module to an electronics technician, to an electronic service.
In the car electrical workshop, make arrangements with them, they will take it out and you take it to the electronics workshop.
 

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Discussion Starter · #4 ·
Hi Guys,
Update!
I found similar BCM on eBay and changed myself. It was really easy. Now everything works fine.
Original: BP4K 66730 F 5190500C3

Replacement: BP4K 66730 F 5190500C3

I attached the pic of both original and replacement part number. Thanks
 

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I also have problems with the lights in the cabin. The lights come on when I hit the BCM, from below. But, first, I will try to fix that BMC module first. Just to make time. I'll let you know the results.
 

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Discussion Starter · #6 ·
I also have problems with the lights in the cabin. The lights come on when I hit the BCM, from below. But, first, I will try to fix that BMC module first. Just to make time. I'll let you know the results.
ok.

I have read somewhere it is because of a relay and it has lose contacts and need re soldering on the PCB. It is little bit difficult to repair but not impossible.
 

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My 2004 2.0L (155k miles) has been doing the same thing for a few years now. My (cabin illumination/parking/tail) lights typically either don’t work at startup but then later come on or they work initially but then turn off briefly for seconds or minutes and then come back on. The pattern appears to be cabin temperature-related perhaps affecting the relay/solder (more on that below). Perhaps hitting it could help as others have noted but I don’t try that.

Like dani mentioned it is the relay on the board that loses proper seating/connection at the solder point. I’ve seen a tutorial somewhere (apologies for no link it was years ago) on how to fix it on the board but it wouldn’t be something I would try without having a backup board on hand because if you try it and end up ruining the board entirely the car is obviously undrivable. The fix was either to resolder the specific relay itself or put the entire board (removed from the plastic housing!) in a toaster oven (and dispose after b/c if heavy metals) at some temperature for some time where it would remelt the solder. The latter method I personally would try after attempting to resolder the specific relay because that sounds like a last-ditch to me. This is all based in what I’ve read on other posts so please do more reading on this as is this is based on my understanding. At 120k I replaced my struts with Koni oranges and I want to say that the stiffer dampening along with the horrible roads where I live have caused this inherently weak-soldered relay to loosen as too many others are experiencing. Perhaps the colder, winter climate this car has not seen until 2017 was also a contributing factor on this relay.

The real issue here is that Mazda should recall this board but I suppose not enough people have been killed in rear-endings at night due to the tail lights going completely out. I avoid driving this car at night because of this problem but I live in the northeast where it snows and it gets dark early in ther winter so this is a risk to me. I will be doing the same as dani and find a board on eBay. They don’t typically go for more than $100 or so and it’s much cheaper than what I’ve seen others quote the dealer will charge ($700+) for what will be a used one since they are no longer manufactured. Of course you risk the replacement board suffering the same issue but at least provides a backup board in case of total failure.
 
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