Last Tuesday, I went to the garage and got into the TReg to go to work. When I started it up, I had an Airbag Fault in the MFI. It was fine when I parked it, and was simply left in the garage overnight.
I searched around for info. Didn't find anything here, but there was a relevant thread on vwvortex (http://forums.vwvortex.com/zerothread?id=1110545&page=1
). From there I determined that the problem may have been any of 4 issues:
- Loose connection in the airbag wiring harness;
Too short wiring harness;
So, I called the service department, and they said this is a new one for them. So I explained that I did some research and told him the four things it looks like it might be. The service rep seemed genuinely interested in what I found, and scheduled me for an appt. the following Tuesday. I asked if they could do some research on thier end, in case they had to order parts. He said they could certainly look, but wouldn't know much until they hooked it up to the computer and looked for fault codes. So, I offered to swing by so they could do that, and be more prepared for the scheduled appointment.
They found code 01520. SM described to me that this code indicates an intermittent fault in the drivers side airbag. They checked the connector and the wiring harness, and said that my TReg benefitted from the running production change - the harness is plenty long so as not to cause undue stress. The procedure with code 01520 calls for a 'guided diagnostic procedure' - according the the SM, this can take anywhere from 2-4hrs (or longer), and may involve several back and forths with VWoA experts. Only after this procedure will they know which parts to order, if any.
They wisely chose NOT to clear the fault then, so they could run the procedure at my servicing appointment.
Well, when they ran the procedure yesterday, it called for them to "pin" the harness. As described by the service tech, Steve, this means to replace pins in various connectors in the airbag wiring harness in a prescribed order, and re-test for the fault. The assumption being that a bad pin, or bad connection to a pin would be the problem, and if the fault did not reappear, then the problem is solved. Steve was not comfortable with this method of diagnosis, as it seems to be stabbing in the dark. Before he wasted time (and frustration for both he and I) he cleared the fault and tested again without changing any pins. Unsuprisingly, the fault did not reappear.
Now, Steve could have changed some pins and told me the problem was fixed, or be honest and tell me he could not pinpoint the problem. He chose the latter. As he explained, the airbag wiring harness is squeezed in pretty tight under the drivers seat along with the battery and another fuse box. He told me he thinks the cover for this is just a bit to tight for how much is under there, and that it would be very easy for seat movement to bend the connection just enough for a momentary open circuit that could cause an intermittent fault. If that's the case, then "pinning" the harness, or replacing parts is a waste of time.
So, my fault has simply been cleared, with no definitive cause. But I have a very plausible explination from an open and honest service tech who I trust (Steve has been servicing my various VW's for 10 years). Finally, Steve said that if the fault came back, he would replace both the wiring harness, and the airbag itself. According to the procedure, if the "pinning" process does not fix the issue, they are to replace the airbag - but do this last. Instead of the tedious hit or miss pinning process Steve would just replace it all in one visit, to save time for him and I.
While I would have liked a more definitive answer, I am very happy with my service experience. Quick, methodical, efficient and honest. And I'm glad to be out of the XTerra they got me from Enterprise - only had it one night, but makes me appreciate the TReg that much more.
BTW - I had the remote range TSB fix done while it was in. Increased range from 10 ft to more than 65 ft.