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How To replace faulty airbag control unit (981s)

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As I cannot insert tags in text I will put those mentioned in this thread up top.  Ian =@T24RES Richard =  @Richard Hamilton Sam =  @fat haggis  

 

April / May 2019 update:

I post this mainly because I have had a very stressful month worrying about my pride & joy but if this can help someone else who is unlucky enough to have  the same  issue,  then  great. 

In early April, I attended the Scottish Scramble and had a fantastic long weekend in the highlands with many of you guys from BoXa.net. I covered 1682 miles over 6 days and the car behaved impeccably except for the run on Friday led by Sam. Part way through the day, I had the airbag light come on, as well as the seat belt light and a warning triangle telling me the start / stop function had been de-activated.

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Apart from the lights, the car worked well, I just had to learn to ignore them until I got home.

Whilst in Scotland, Ian plugged the car into his Durametric reader and found he could not communicate with the AirBag Control Unit. When I got home, I asked Richard Hamilton to plug in his pwsis reader and he confirmed the same. I then checked the fuse (D1) in the right hand bank (that is the driver side in a uk car) and found the fuse had blown. I changed the fuse and it went pop as soon as you turned on the ignition (you could see the spark). The conclusion was that the AirBag Control unit had gone faulty and that it needed to be changed.

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The bad news is that a new part from Porsche was about £600 and I was too scared to ask how much to fit.  I do not have a Porsche warranty, I took the risk, put £3k in the bank just in case and it was at this point I was wondering if I had made the right decision  😞

I spent a few days calling my Indy, a car electrician, various AirBag specialists with varying responses. My Indy would not touch it and told me to go to the OPC. The AirBag man told me he doesn’t do Porsches because they are too hard to program after. I was even told that you could not replace the faulty unit with a 2nd hand unit, only a new unit from Porsche would do. There was a theory that the new (replacement) ABC unit would have to be coded to your car and only Porsche could do that. Thankfully this turned out to not be true and after a few more phone calls , I came up with a plan:

1.       Buy a secondhand ABC unit from ebay (The AirBag Team) £98

2.       Remove faulty ABC unit from my car

3.       Send both old & new units to www.crashdata.co.uk

4.       Crashdata would copy data from old ecu to new ecu  £96

5.       Fit replacement ABC unit back into car

I discussed this with both Richard and Ian and both felt that this should work but there was a risk that the replacement ABS unit could also “disable” itself if the fault was in an airbag or seat belt pre-tensioner. It should be noted that this fault was not related to the changing of the seat belts mentioned in a previous post because I had driven the car for about 3 weeks and completed about 800 miles before the lights came on.

If I am honest, I wanted to try this plan because the potential cost at the OPC could have been thousands. I had read in many forums and on the AirBag specialist sites that the standard fix (recommendation) by the OPC is to change all air bags and seat belt pre-tensioners as a just-in-case measure – ouch !!!

Richard provided me with sections from the Porsche manual telling me how to take the car apart. The ABC unit is under the air con control panel and the PCM so most of the centre console has to be removed.

Ian offered to help so the job was on.

On April 19th, I bought the 2nd hand unit and moved up from the original .03 version to an .08 version based on Richard’s advice. The theory was the later version would be a better model and any faults in the original version might have been fixed.

On Easter Monday, we took the centre console apart. The manual sections were fantastic in leading us through the job but what really helped was that Ian had taken most of the centre console apart before in his own car. The hardest bit is pulling apart plastic panels and not breaking clips. The manual tells you which way the pull which is very helpful. The faulty ABC unit was out in 90 mins so we then went and had a BBQ 😊

The replacement ABC unit arrived on wed 24th April and I quickly packaged both of them up and sent them off to the crashdata guys in Liverpool. They worked their magic and found a way of copying data from the faulty (dead) unit to the replacement unit. This is the most important step as without this the car would not recognise the new unit (I now believe this is what many of the specialists called “programming” and was the reason they could not do it. It is also possible to use the pwsis system to store old data and restore it after the unit is replaced, which I guess is what Porsche does but this only works if you can talk to the old unit (Not possible in my case)).

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Both units came back on the 30th April and over the next few days, I started putting it back together …… slowly & carefully. On the 3rd May, Ian popped over and we finished the re-fit in under an hour.

Once a new 5A fuse was fitted and the battery re-connected, I very warily turned on the ignition. Three of the four problems were solved immediately. The D1 fuse did not blow, the seat belt light worked correctly and went out when I put my belt on, the warning triangle for stop/start did not re-appear BUT the airbag light was still on.  I then took the car round to Richard who reset the old air bag faults and hey presto, the light went out and stayed out for my drive home. I have driven the car again today and so far everything is fine.

I need to do more miles to prove this is a permanent fix but at this moment it looks like our £200 fix has worked and I have avoided a huge bill at the opc.

I must say a huge thanks to Ian for all his help and Richard for his technical advice. Without these guys, I would not have tackled this job through fear of not knowing what I was doing or the fear of breaking something else.  

So, lessons learnt for myself …..

1)      Don’t believe everything you are told, ask more questions and talk to lots of specialists until you find that person who gives you confidence that he knows how to fix the problem.

2)      Have a go, follow the instructions and find yourself some good mates who can help 😊

3)      A faulty AirBag Control Unit can be replaced with a 2nd hand unit as long as you get your old data loaded onto it correctly. You do not have to buy a new unit.

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Steps to dismantle the centre console:

1)      Remove side panels  (both sides – prise out at the back  and slide panel backwards)

2)      Remove 1 x bolt on each side and remove side/front triangle shaped panel. This needs to be slid forward and down/ push on tab where you took bolt out at 45 degrees down & fwd

3)      The passenger side panel (2) has charge point which needs the lead unplugged

4)      Remove gear knob (twist bottom ring and press button on top – need ignition on)

5)      Turn off ignition – Disconnect battery at this point

6)      Remove trim that sits round all of centre console (prise up carefully)

7)      Remove panel that sits round gear stick

😎      Remove switch panel (sports button, rear spoiler etc) / Disconnect small plug

9)      Behind the seats, remove speaker covers

10)   Pull out carpet wall from behind seats

11)   Remove oddments tray (small square tray for coins in middle of centre console). Slide forward and then up

12)   Remove cover at back of console that touches the carpet wall

13)   Remove arm rest / tray lid. Need to push out pin and release end of spring

14)   Remove two bolts from tray under arm rest / pull the tray up carefully. Two of the lugs here were held very strong.

15)   Remove electrical connector from rear of the tray

16)   Remove 4 bolts that hold PCM screen in place

17)   Remove 5 connectors from back of PCM

18)   Remove Air Con panel and remove 3 x connectors

19)   Remove 3 bolts from both sides of the black centre console frame

20)   Remove black centre console frame (prise back half up and slide frame backwards carefully)

21)   Remove black mesh side panel on drivers side (prise out front fastners but watch out for rear fastners where the last one goes fwd and the one just in front of it goes upwards)

22)   If you look into the hole where the air con panel was, you will see the ABC unit.

23)   You need to push the grey lever across on the big yellow connector and release the connector

24)   Get a 10mm spanner/socket and remove the three domed bolts. They are NOT security bolts. The two r/h bolts can be done from the r/h side through the hole with a ring spanner where the black mesh panel was. The l/h bolt can be removed from above through the air con panel slot with a socket.

25)   Re-install is the reverse of above with one added step:

26)   Insert a new 5 amp fuse in position D1 in the r/h fuse bank before you connect the battery.

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All the bits laid out on the bed to keep them safe and help me remember the order to re-fit

 

If anyone else gets this problem and wants the manual sections, let me know

As for the 981, we are off to Switzerland on June 13th for a 9 day trip so fingers crossed this is a permanent fix

Cheers

Tony

Edited by tony_zx9r

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😎

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Glad you got it fixed mate and cheaply 👍 and another fix for the 981 without the Porsche tax 

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Great persistence in not letting yourself be fobbed off that it can't be done. Hopefully save a few other forum members a big bill in the future🙂

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The only thing I would like to add to this excellent write-up is that I'm not 100% convinced that the data from the failed unit has to be copied to the replacement.  When I was doing the reset at the end of the process, I looked at the coding options, and there were options to change model/isofix etc., and it appears these could be changed.

I don't blame Tony for adopting a 'belt & braces' approach, and doing it that way ensured success.  However, there is a nagging feeling that I wish I had been there when Tony & Ian took the failed unit out, and could have tried just changing the coding on the replacement unit to suit.

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22 hours ago, Richard Hamilton said:

The only thing I would like to add to this excellent write-up is that I'm not 100% convinced that the data from the failed unit has to be copied to the replacement.  When I was doing the reset at the end of the process, I looked at the coding options, and there were options to change model/isofix etc., and it appears these could be changed.

I don't blame Tony for adopting a 'belt & braces' approach, and doing it that way ensured success.  However, there is a nagging feeling that I wish I had been there when Tony & Ian took the failed unit out, and could have tried just changing the coding on the replacement unit to suit.

I think you are right Richard, after all, that is probably how Porsche would do it if the original unit had failed like mine and they had to set-up a brand new unit.

But you know me, (I used to be a project manager), I will always opt for the plan that has a greater certainty of success ...... I can't help myself, it's how I was trained 🙂

Thanks again for all your support

cheers

Tony

 

 

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Excellent writeup Tony and a project well managed😁 great assistance from fellow BoXa.netters 👍

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Nice write up. Glad to see it's sorted without Porsche Tax :)

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