The saga of the AirBag Warning Light | Performance Magic

Ramblings from a Sysadmin

July 17, 2015

The saga of the AirBag Warning Light

About 6 months ago our car (2008 Nissan X-Trail) started to have it’s AirBag light flash. This could be a worry we thought. After some googling we found a way to reset or go into a new diagnoses mode. This involved carefully timed ignition key turning with the airbag light showing up on the dash. (as it turns out there are at least a couple of these combinations which interact with various systems in the car)

After several months and the 6 monthly trip to the mechanic, we decided we should probably get this fixed. The mechanic was able to provide us with 2 codes. No googling was able to help as to what these codes meant. A trip to the auto-electrician was required.

The auto-electrician wasn’t sure what the codes were and needed to look them up. But said that it could be several systems including an airbag (we have several) or any of the connecting harneses.

The auto-electrician called about a day later and provided details of the codes.

– B1049 – Steering wheel airbag

– B1129 – seat belt

The focus from the auto-electrician at this point was solely on the steering wheel air-bag. He provided quotes for several hundreds of dollars for a new airbag, new clock-spring (what’s a clock spring I hear you say, more on that later), 2nd hand versions of these or some combination of each, pluse several hours of install, test, repeat…

It was about this point that I remembered I had acquired the ESM (Electronic Service Manual) for my type of X-Trail (T31) at some stage in the last few years.

I proceeded to review the manual to see what it had to say. The manually is horribly organised, only seems to work in certain versions of IE and with certain security controls turned off. It was also made up of single pdf and html pages. This made the process of finding and understanding the codes, and later understanding how to dismantle the car, very difficult.

From my observations and understanding from the manulal I made a few assumptions of the auto-electrician and their provided diagnoses.

– They overlooked the fact that there were 2 codes (the focus seemed to be on the steering wheel only) could this mean that the loom was common for these 2 points or did the ACU (Airbag Control Unit??) have an issue.

– They didn’t appear to have an electronic diagnoses system (this is an assumption only by the way they were talking)

– Whatever manual or documentation they were reviewing or their interruptation was incorrent ( the second code was for the drivers side seat airbag, not the seat belt)

– Why not test the clock-spring? (after all it is just an extension lead, right?)

At this time I wasn’t keen on going back to these guys, so I decided to have a crack at it myself. (after all I consider myself an engineer and once installed car stereos for a living for a brief time)

I used the manual and followed the guides to pull each system apart.

Safety first! Disconnect the battery and wait 3 minutes. The airbag system must employee some large capacitors incase cables are cut during a collision.

This was the first hurdle. Our car was fitted at the dealer at purchase time with a battery backed up alarm system. Usually these systems have a key for the siren to disable the internal battery. Well no key was ever provided and nothing in the supplimental documentation provided an answer on how to disable it.

Off with the air intake system. Find where the siren was mounted, and how. Undo the mounting bolts and remove from the mounting bracket. Now what to do with it?

I looked at it and found that it had 4 philips screws. I figured it would internally have a way to disconnect the siren. I disconnected it from the car wiring loom, quickly removed the 4 screws and disconnected the siren from the small circuit board. Silence! (Later I just put it under a big pile of blankets. just as quiet, and less painful.)

Once the power was disconnected and the alarm was quiet I proceeded. The centre console needed to come out so I could gain access to the ACU. I removed all the cables from the ACU and cleaned them up, leaving them disconnected for now.

I then removed the seat and tested all the cables and between the seat and the ACU. Cleaned the connectors there too.

I then turned my attention to the steering wheel. I carefully removed the airbag, and then the plastic housing around the steering column. Disconnected the wiring loom. I tested the clocksping (simply just checked that for continuity on each cable in the pair and no closed circuit.)

At this point I was able to confirm that the wiring loom looked all intact and for both routes and they routed in different directions. So nothing was obvious at this stage.

I put everything back together. Connected the battery, installed the siren and performed a reset with the special key combination.

The light did not flash…

Test drive time.

Just around the corner the light started flashing. The questions were numerous. Had I made a change to anything? How could I test? What if it was this, or that or, or…

I needed a “Consult III” as the service manual reffered to it as. (This is just Nissan’s eletronic testing harness that attached to the CAM system and requests diagnoses information from the various on board systems)

I went back to my mechanic, and they reluctantly scanned the car again, but wouldn’t reset anything. Great. This time, only one code. The steering wheel.

I had already checked the clock-spring, so it can’t be that. Let’s find an airbag. I found a similar airbag on ebay (it was for the Ti T31 so had some extra buttons), and promptly ordered and paid.

It arrived, I installed it and … light flashing. WTF? Maybe there is a problem in the loom or the clock-spring has an intermittent fault.

Lets ask the eBay member that we got the airbag from if they have a clock-spring. Sorry, none at the mo. Looked on gumtree and found someone wrecking a T31. They still had the clock-spring. (though it was more than the airbag). Oh well, still cheaper than the auto-electrician.

Drove and picked this up. Same thing. Disconnect alarm, battery, airbag. But now I needed to remove steering wheel. Reasonably simple. Dismantle the steering column and remove the clock spring. Again pretty easy. This was too easy.

Looked at the clock-spring and worked out the centre position so that it was installed correctly. Re-installed the original AirBag. Installed, battery, alarm and reset the ACU. Light off, and staying off.

Success.

I now wanted to return the AirBag as the return conditions were “Return for any reason within 60 days”. This was one of the reasons I chose to buy from this seller. A few hours later, I got a phone call from the seller, “You can’t return it. We are reporting you to eBay. If you do it will be less the postage”. That wasn’t a very friendly phone call. I kicked off the return via eBay and also lodged a complaint against the seller, just incase. eBay were great. Great response, and they ensured me they had my back.

The next problem was returning it. (Seeing a pattern? Almost endless trouble). Found a parcel service online run by Fastway. Put in your details, print the label and drop it off. Too easy. So the payment succeeded, but the site responded with “an error has occurred”, and no human to ring. I wanted to send this today. The online form said they would respond within 48 hours…

Found a number to call, and got on to the Fastway helpdesk, where a great person named Ryan helped me get a refund, and said to try again. And I did. And again it failed. So I got another refund and went to Australia Post.

Funnily enough the AirBag was delivered very quickly and I got a full refund from the original seller without any issues. I still can’t believe why companies and people want to go to so much effort to try and make your life hard.

© Greg Cockburn