[ateszaholdjaro]

Hi guys,

I've been getting random safety belt and airbag check lights on my dash, so I plugged my Carly in, and did a quick test. It came up as being a Safety Battery Terminal problem, but up on inspecting it, it didn't seem like it has blown or anything and the car has been functioning perfectly since (~2k km). The error code is 0093B2.

Since it has been there for quite a while now it is bothering me to heck, so today I did a closer look at the wiring around it and found a wire whichs end was cut, and wired on a resistor of somesort. I'm asumeing that might be the cause of some problem. I wanted to find were it connects, but ended up with nothing. Maybe some of yall could help me with where the end of this cable would go originally? I attach a photo about the connector on which the resistor itself is wired onto.


Edit: also here is my last 6 digits of my vin KU35696, it's a 2005 320D, without IBS.

[Serf27]

The resistor is wired to that?

The other end of that connector goes to the BST on the + battery cable.

[ateszaholdjaro]

Yep, here is a picture. I know, its anything but nice.



So I have to connect it under the positive terminal, or into the "fuse" between where the two terminals connect?

[VehementCrom]

It plugs in on top of the battery, in the fuse block thing that covers the battery. There is another small black connector which plugs in opposite of that one. There is also one small black connector that is used for shipping purposes and is unplugged.

[ateszaholdjaro]

Thanks!

[PhaseP]

You may still get that even after you connect it back to where it was supposed to be. My guess is the little flimsy connector that connects to the BST at the batter plus post got knocked out once during battery replacement, and after that it was not holding well, causing this code being thrown. And previous owner as solution ended up connecting a resistor of same value that the computer is expecting to see when it runs periodic self diagnostics on that system.

You can see more about it here:
https://www.e90post.com/forums/showthread.php?t=1077369

It is not an uncommon problem. Some of the pictures in that thread will have different style (later version) BST, but in the end they work the same.

As to how BST works, the wire goes to a small pyro charge igniter, which gets ignited by car computer in case of an accident. This small explosion inside BTS disconnects the plus wire from the battery plus post. From outside it would still look like connected though.

The computer periodically checks the resistance on that wire and if it finds it is not within the range it expects it to be, throws that code and lights up that airbag light.
If I remember correctly you need to manually clear that code, computer doesn't clear it by itself after it finds the expected resistance on the wire.

[Serf27]

Another scenario is the BST has been deployed and has been forced back together. The MRS module no longer reads the BST as functioning and triggers and SES light.

The resistor is there to trick the MRS module.