Originally Posted by
Krusty900
Hi.
Just wondering if this should have happened.
My partner was stopped at some lights behind another car, got distracted and took her foot off the brake and the car went forward (dsg) into another car and the passenger airbag, driver airbag and drivers side near the pedals airbag deployed.
Is this normal..? is it a fault..?
The person who she hit, basically didn't know she hit her and the police who attended were bewildered at the damage (passenger side airbag broke the windscreen).
Guessing it is probably going to be a write off, but wondering if I should contact VW about the airbags being deployed..?
Krusty: Accurately understanding what happened in an accident where the airbags have deployed is an arcane science - as well as being a bit of witchcraft! So it's very unlikely that that anyone here will be able to help (no offense intended to Umai Naa whose knowledge of VW stuff is impeccable and without peer on this forum).
But perhaps the picture below will help in understanding the degrees of freedom that the mk7 uses in making the ultimate decision to fire-off the pyrotechnic igniter in the air bags:
As you can see, airbag deployment is quite a sophisticated decision making process that is ostensibly controlled by the module labelled J234. The algorithm that J234 uses for this purpose is a balance between a quick response in a severe frontal collision and the avoidance of deployment in less hazardous cases. But there is information from multiple sensors that is used in the decision making process.
I'm by no means an expert of the mk7's algorithm, and without wanting to understate the sophistication of the system, my understanding is that airbag deployment is all about measuring deceleration and listening for certain frequencies in the car that are formed during the fast deformation of supporting structures in the front end of the vehicle. Again, my understanding is that these frequencies spread through the body structure at high speed and very quickly provide precise information about the severity of the crash. It's a bit like an echo sounding system in a submarine except that J234 is a passive listening device
As the picture above also shows, there are acceleration sensors and front door pressure sensors placed at strategic locations in the mk7 which also contribute to the airbag deployment algorithm.
As to which of these inputs to J234 was the most critical in the decision to deploy the airbags, the answer can only be found by interrogating PIN #15 (see the wiring diagram below) on the car's OBD port using a special device - which is very different to diagnostic devices that lot's of us "nerds" use (like VCDS)
Unfortunately, the cost of even the most basic airbag control module reader (see HERE) is about $5K ($AUD).
So, here's the real question - how badly do you want to know the answer to your question? 
Don
Last edited by DV52; 15-09-2017 at 04:34 PM.
Please don't PM to ask questions about coding, or vehicle repairs. The better place to deal with these matters is on-line, in the forum proper. That way you get the benefit of the expertise of the wider forum! Thank you.
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