BMW Multiple Restraint System (MRS) Data

[Witsend]

2011 BMW 328I sedan with 120K, no accidents . I was expecting the MS908P to be pretty strong with Live MRS system data and be able to graph and watch resistance values of airbag circuit PIDS change and spike while wiggling harnesses , but there only seemed to be less than a half dozen very rudimentary ones like if seat belt was engaged or passenger airbag switch is on or off
The aftermarket repair software information didn't even offer MRS code charts, let alone diagnostic help with any specific codes.
I have a code 9419 (MRS) left belt force limiter. I thinking it is something behind the left B pillar inside the driver side "front" seat belt re-tractor assembly, the BMW parts guy tends to believe I need to replace the LF seat belt pre-tensioner but the code description of left front belt "force limiter" seems to me like the opposite of what the pretensioner does when it deploys.

[Witsend]

Yep , LF seat belt pre-tensioner /end release buckle assembly fixed the 9419 code. Sure glad it wasn't a Miss on the MRS or I could be married to it.

[tech25]

glad you fixed it, just read it now.. regarding BMW live resistance readings though in a scan tool, yes, its true you cant really get "live" readings, would be nice though,

instead, even the factory tool ( BMW ista ) will read the resistance one time, not dynamically. then you can unplug the airbag for instance, then "re-check" the resistance again and it will update it.

note.. a lot of factory tools now are offering really good walk throughs, or diagnostic trouble charts/trees...what ever... on their faults. and its not like suretrack which is only generic obvious stuff. it will walk you through pretty much ALL fault codes with wiring diagrams, description of operation, repair instructions, basically everything..

[Witsend]

glad you fixed it, just read it now.. regarding BMW live resistance readings though in a scan tool, yes, its true you cant really get "live" readings, would be nice though,

instead, even the factory tool ( BMW ista ) will read the resistance one time, not dynamically. then you can unplug the airbag for instance, then "re-check" the resistance again and it will update it.

note.. a lot of factory tools now are offering really good walk throughs, or diagnostic trouble charts/trees...what ever... on their faults. and its not like suretrack which is only generic obvious stuff. it will walk you through pretty much ALL fault codes with wiring diagrams, description of operation, repair instructions, basically everything..
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Went to pull the 328I out of the garage and the 9419 code persists
looks like I will remove new and reinstall the old part and just ship it, and eat the new part or try to sell it off E-bay, if one last check of connector being fully seated. Next to nothing about diagnosing and fixing 9419 code on the internet I'm sure if it were mine I would do pin out tests from the MRS module, but hate dealing with tedium of such tiny terminals that a straight pin would spread and damage, the ecu connector backs are often covered , shrouded to prevent back probing and my wire piercing tool is like for 14 gauge wires , not tiny 20 gauge ones.

[tech25]

if you have time, maybe try this...

you stated this is a sedan... because that fault also refers to a rollover bar, right open circuit.

sedan shouldn't have a roll over bar... other than that the fault states, " belt force limiter, left "

have you also tried a hard battery reset??

edit..I may be wrong because i see a transistor after 30, which means it may be 12v switched at pin 1, so you may not have 12v at pin 1.

if this is the case, then one would access the mrs module and test the wires from the mrs module, to the limitor connector

[Witsend]

if you have time, maybe try this...

you stated this is a sedan... because that fault also refers to a rollover bar, right open circuit.

sedan shouldn't have a roll over bar... other than that the fault states, " belt force limiter, left "

have you also tried a hard battery reset??

edit..I may be wrong because i see a transistor after 30, which means it may be 12v switched at pin 1, so you may not have 12v at pin 1.

if this is the case, then one would access the mrs module and test the wires from the mrs module, to the limitor connector

Thanks for the more detailed view of the circuit with explanation. It is definitely a 4 door sedan. I did not try a hard battery reset, just tried erasing all the module codes and then tried clearing the MRS module code separately and it did not clear. It also had the VTG oil wear code (for that $60per liter of 75W weight transfer case oil change and reset), and another code for foot well module programming sectors used is high I would have liked to have spent more time on it but the terminals and wire sizes are so tiny and shrouded on so many newer cars now that you still can damage terminals back probing.IMO piercing such tiny wires is dumb. Wish I just could have had a pretensioner substitution resistor to plug in and drive around a bit first. Now I own a brand new BMW pretensioner assembly I can plug in for testing purposes, but I still really don't know if it's a defective pretensioner out of box either, and it be either expensive or risky dangerous business testing pretensioners or airbag resistance values to write down their resistor specs while removed. Guess could use very long leads like the Wiley E. Coyote with the ACME Dynamite and a high impedance multimeter with the correct selected range. In all likely hood, "high impedance" meter set on low range (Not Auto RANGE), it probably not have enough current flow to create enough heat for the igniter inside to be able to set off igniter charge immediately , maybe if the hi impediance meter leads remained on the long wires leading to the airbag kept a safe distance away it wouldn't detonate until Wiley E. Coyote goes to check the connections.

[Witsend]

I know, I know. You should never test the actual components of an AirBag system with a DVOM. I just had to know if the pretensioner I bought was actually good or not, but and yes I'm still alive. Guess if I made a Simulator for quick testing purposes, versus removing the seat, the console and airbag controller connectors, I guess around 2.3 ohms soldered on a salvage yard pigtail be where I would start

[tech25]

that appears to be correct resistance, so the part is the not problem. thats why earlier i said to test the wiring from the mrs module to the tensioner, if the wiring is good. then its a module. ( or a hard reset, or repogram/code ) and test

[Witsend]

that appears to be correct resistance, so the part is the not problem. thats why earlier i said to test the wiring from the mrs module to the tensioner, if the wiring is good. then its a module. ( or a hard reset, or repogram/code ) and test

Thanks again . That was the resistance measured on the new part. The old part resistance was never checked, so if I get the car back, before pulling seat and console I just might be brave enough to test the old one , and only if out of spec or open , I'll plug in the new part again and try that hard battery reset procedure, (even though I don't feel up to reinitializing, windows, sun roof and other cr@p that comes with doing that)