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The airbag light is on on my 525i
I had it in with Logic Automotive for ABS module repair and the following came up on the diagnostic (no code)
Restraints : Airbag
"battery positive terminal isolation 1: resistance too high'
Anyone any idea what the fix for this is? Peter at Logic had never seen this fault before
This relates to the BST, or Battery Safety Terminal. There is a pyro-technic charge built in to the positive cable that connects to the battery. In the event of an accident the airbag module sends a signal to the BST & the charge explodes cutting the power to the car (the cable breaks with the mini explosion).
"Resistance too high" probably means the little black cable on the BST is disconnected, you will see a black/yellow connector on this.
When you power on the car the airbag module "checks" all the satellite devices (e.g. Airbags, crash sensors, seat mat, seals belt tensioners & BST). It does this by measuring the resistance in ohms of each of the devices, if it comes back greater than 6ohms from any of these circuits then it will trigger a fault as being present & illuminate the airbag light in the instrument cluster.
If it is to low it will also trigger an airbag light, eg if someone used a plain piece of wire to bypass the airbag or sensor.
There also could be a problem with the software version on the repaired module. I hit this issue on a car a few years ago.
This fault is actually quite common, second only to a broken webbing in the passenger seat (occupancy sensor).
Here is a diagram of the BST:
http://i.ytimg.com/vi/c26Jq1O1m0M/hqdefault.jpg
The fault may be with the igniter capsule too.
http://www.bimmerfest.com/forums/att...3&d=1316667714
Here's the unit that might need replacing:
http://i568.photobucket.com/albums/s...0-%20BST/2.jpg
http://www.bimmerfest.com/forums/att...8&d=1326418113
Thanks for your input Rebel Ranter very informative. I guess I need a new BST then. Do you know if they need to be specific to the 525i E39 or will any e39 one do?
Hi, they are the same part number for most RHD e39 unless they have some really obscure options; 12 42 1 436 885. Part #1 below:
http://bmwfans.info/parts-catalog/E39-Sedan/Europe/525i-M54/R-A/nov2002/browse/engine_electrical_system/battery_cable/
http://i175.photobucket.com/albums/w...pspzj9gdrg.png
Price: € 194.60 EUR (on www.carparts-pros.com, add €17 for delivery, plus €5 for PayPal)
Thanks ....that's quite expensive . I'll try and pick up a second hand one
^^^ why this forum exists! Nice one Mark!
will be nice to change it :hehe!:
Did be very tempted to try connect up a seat occupancy bypass sensor to the two little black wires. If it doesn't work then you would be buying a replacement unit anyway.Quote:
Originally Posted by Billy Greenbush
If it does work just bear in mind that when you crash the battery won't disconnect automatically.
It was suggested by BavarianCare on the other forum that I could disconnect and code this out ? Know where I can get this done in Dublin?
I called into to Courtney's and they sat they would need the car for the day to find out exactly what's going on with it. Probably needs that new part but they need to check it themselves
If it's possible to get it coded out I would....have spent a bleedin fortune on her recently so would like to avoid anything else if possible
I had a bit of a mishap when coding an Airbag module so I the doing them. No, the airbags did not explode!! I just tried to code out the passenger occupancy sensor & the Airbag ECU hit an internal fault killing the module. Apparently I should have coded out BOTH the passenger & driver side codes at the same time, even though there is no driver's side occupancy sensor.
Do you know of anyone up in Dublin who could code it out ? Thanks
Mick in Germaniks could do it no problem.
hi i just see that you have problem with airbag and I have in the pass same problem and was showing that positive cable fault but on the end was air bag module i change the module and all fix. that what i have in my e39
Hi Daniel- do you have a spare airbag module for sale?Quote:
Originally Posted by daniel teichert
Hi Billy, I have an airbag module for an e39 for sale. L
What's the part number on yours?
HI Rebel- not sure how to find the part number for airbag module....where would I look?Quote:
Originally Posted by rebel.ranter
PM me the last 7 digits of your VIN & I'll let you know if my one suits your car.
The airbag module MRS (Multiple Restraint System) changed for cars produced after February 2001. Cars earlier than March 1999 also had a different module, I believe the pre '99 cars had a single stage deployment system where as later cars had a two stage system.
Here's my experience with a friend's e39 a few years ago:Quote:
BMWFans.info Airbag Control Module Info
- After Feb 2001 - MRS 4 Part Number: 65 77 6 920 848 or 65 77 6 919 789 (all e39 models 520-> M5)
- March 1999 to Feb 2001 - MRS 3 Part Number: 65 77 6 900 727
- Before March 1999: (Not sure what official name for this system is) Part Number: 65 77 8 374 798
http://www.bimmerforums.com/forum/showthread.php?1910637-HELP!-E39-Airbag-Module-(MRS4)-won-t-code!
Thanks man
It's G053070
Thanks man
It's G053070