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Airbag warning and OBD one

pietrzj

Well-known member
Joined
19 Mar 2014
Messages
309
All,

For some time I have had a warning light that goes out after about two minutes and I need to fix it.

I have an OBD2 s/w pack and interface cable that I bought a few years ago an have never used (cheap from ebay, which I bought for a 51 clio I had), but I noticed the connector is the same type as the 993.

As my MY is 1994 and the connector cover says OBD not OBD2, I am assuming if it works the info I get will probably be limited. I am hoping it will tell me which airbag is reporting a fault. Failing this I am guessing I will have to disconnect the battery, wait a bit and access the orange conector to disconect the steering bag an insert a 2.8 ohm resistor in its place to see if it is that one that is keeping the light on for two minutes. Then move to the passenger unit if there is no change.

Is this the best DIY approach or are there other techniques I could consider. I have an MOT coming up so want to know where the fault is rather than replacing both bags.

Some other threads also suggest the cause could be dry solder joints on the clock PCB? Anyone got any details about this?

I am handy with a soldering iron if that s the route I need to take.

Any help gratefully received.

p.s I have tried the old ignition on with foot on throttle method, but no flashing lights that relate to airbag faults.

If all else fails its the dreaded Porsche Main Dealer

Jan
 
I would just say get an indy to read out the fault codes for you , it will be far quicker and cost effective i would think and after that you can choose to repair it yourself or get a quote from them.
 
NottsRS, thank you for your reference.

An off-the-shelf OBD reader/scanner will only at best be able to communicate with the Motronic engine management system in the 964/993.
Don't bother with the OBD1 or OBD2, this is not the problem here. If you have the round 19-pin OBD connector you will need a 19-pin adapter to use a OBD tool. Beware, most such adapters on eBay/Amazon/elsewhere are wrongly connected. I sell a proper cable made according to Porsche specs.

There's only a handful of systems that can do all the OBD-connected things in our cars. (Motronic, ABS, air bag, alarm and climate control)
*The Bosch Porsche "hammer" (KTS 301) or later Bosch Porsche tools as PST2 or PIWIS
*Freeware Rennlist Scantool Windows software (serial port adapter as the T-OBD needed)
*Durametric Windows software with a proper (original) serial cable
*Jenniskens OBD UDT/PDT999 diagnostic tool

Cheers,
Tore
 
Thanks all. My car does have the OBD2 connector at least. I have now made the situation worse by inserting resistors instead of the airbags. Now the light comes on on the check, goes off briefly (less than a second) the comes on all again - permanently. Have put everything back to normal and will try to see if at least i. An get back to it only being on for two minutes.

Will ring the indy tomorrow, dont have long until the MOT test!!!
 
I have a similar problem in that the airbag warning light does not go off for about two minutes after starting the car. I have installed a Cup Steering wheel and deleted the air bag and thought the resistor would remedy the situation as I thought the issue was the air bag itself but alas no......it always goes out after 2 mins.

Spoke to our Rennlist Buddies and as the solder lines at the rear of the clock module detoriate this is one of the symptoms - fix is the responder the connections - haven't attempted it yet and won't as my soldering skills are terrible!

Let me know how you go.....
 
Well I think my clock connections are good.

Does anyone know what actually triggers the bags to go off? I assume there would have to be some sort of switches (inertia?), or is it triggered off a rapid decrease in speed? The only incertain connections in the wiring diagram seems to connect to the alarm system and imobalizer.

I am sure my old clio had bright orange switch units around the car that would trigger the airbag if they were hit.

No such thing can be found so far oin the 993 so maybe they are integral with the bags?

I am running out of time here, I don't want to take it to the indy only for them to scratch their heads if I can help resolve it in this forum.

I am sure it would take them hours and hours to find a clock dry solder joint for example, but if I can rule out as much as possible that will save them time (and me money).

Jan
 
Just found this...

The Boxster also got a new airbag control unit like the 993's, with its internal MEMS accelerometer crash detection. The control unit will store up to ten faults, with a start-and-stop log kept for each fault. Data can be accessed and downloaded with the PST-2 or PIWIS testers. As in the 993, the Boxster control unit does not need to be replaced until the airbag has been triggered three times or if its fault memory cannot be deleted.
 
I dont really know 993 systems but on newer cars if theres a fault with the airbag system the light stays on and will stay on all the time there is a fault code even if the system has been repaired.

i thought it was a one time use airbag control unit on the 993 but the boxster onwards was a 3 time use :dont know:

It really needs a fault code read out to go further .. a code or lack of one helps point us in a direction .

From the description you have given of the light switching off after 2 mins then i would lean towards it being the control unit .. i know 996 onwards and they do give strange faults at times .

I mentioned on your other post its all in one unit now .. not seperate .

DO NOT what ever you do remove this unit with the battery connected or ignition on !
 
pietrzj said:
Well I think my clock connections are good.

Does anyone know what actually triggers the bags to go off? I assume there would have to be some sort of switches (inertia?), or is it triggered off a rapid decrease in speed? The only incertain connections in the wiring diagram seems to connect to the alarm system and imobalizer.

I am sure my old clio had bright orange switch units around the car that would trigger the airbag if they were hit.

No such thing can be found so far oin the 993 so maybe they are integral with the bags?

I am running out of time here, I don't want to take it to the indy only for them to scratch their heads if I can help resolve it in this forum.

I am sure it would take them hours and hours to find a clock dry solder joint for example, but if I can rule out as much as possible that will save them time (and me money).

Jan

964 and 993 system same same - some further reading

https://rennlist.com/forums/964-forum/23104-clock-repair-airbag-light-diy.html


http://p-car.com/diy/clockrepair/
 
airbag

3 years ago I had airbag light on and it was knackered control module which was replaced by one with a 996 part no. Not cheap at £540
 
Just a thought but i was replaceing an indicator stalk on a 993 today and theres an earth wire that goes from the clock spring to the wheel .. ive seen this break in the past and cause intermitant airbag faults as it can make and break a connection ..

Pretty quick check .. just undo the airbag screws lift it up and check the brown wire .. T30 torx are the airbag screws and if your going to disconnect the airbag then battery disconnect first :)
 
Success!

Took it to my IPD and they detected the following codes:
AIRBAG:
19 - Airbag warning light
17 - Power supply
5 - Ignition circuit, passenger
2 - Ignition circuit, driver

Also a few codes in other areas too (I will raise a new post)

They cleared the codes and the alarm light for the airbag system works correctly.

Thanks for your help.
 

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