Technical Airbag warning light - what are the risks ?

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Technical Airbag warning light - what are the risks ?

zenpunto

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Jun 15, 2009
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Hi all,
I have a 1997 Mk.1 Punto 60s which has just passed it's MOT following a few repairs (new radiator and new rear brake shoes for example). I thought all was well until this morning when the red Airbag warning light came on (as usual) on start-up but then stayed on ! After a few km I stopped, checked the fuses (nothing seemed amiss) waited a while, restarted, and the the light is still on. I did about 60km yesterday and no problem so it's a mystery as to why there is a problem today. I have a few questions please;

1) If the red light is on does this mean that the airbag system is no longer working ? Is there any risk of it going off suddenly while I'm driving ? I read in another thread here that the airbag is probably useless by now after 22 years anyway - is this likely to be true ?

2) If I need to have it fixed what are the approx. costs involved ? Can the work only be done by a Fiat dealer or by any garage ?

Many thanks for reading this and for any useful advice !
 
I should add that there is only a drivers airbag in my car and that I've checked the fuses (those in the glove compartment and behind the cover next to the steering column), the seat-belt works fine, no other warning lights are on, and I can find no wires under the seat that might need attention.

Anyone got any suggestions ?
 
The "ECU" is located under the centre console. It has everything in it apart from the airbag and explosive charge. Remove the battery and wait half hour. Then check the connectors to the ECU and airbag. If all seem ok then reconnect the battery. When turning on the ignition for the first time though do this from outside the car just in case. If the fault is still there then look for a secondhand ECU.
 
Thanks Noddy ! I undid the cowl under the steering wheel earlier to see if anything was amiss and saw a rectangular white box . . . is that the ECU ?
 
Airbags are made to last the lifetime of the car is what most marques say... But fiat are never gonna tell you how long they think a mk1 punto was meant to last, probably not this long haha.

As far as I know, so don't quote me on this, what i have figured out by messing with MultiEcuScan, the only things that can make the airbag light come on and stay on are:
1. fault with the crash sensor (as in not getting expected value, which could mean an issue with the sensor itself or the wiring to and from it)
2. low voltage to the ecu
3. Higher or lower resistance than expected from the airbag itself
4. airbag circuit open circuit

So this should be pretty simple to diagnose with a multimeter and few resistors. I think first thing i'd try is disconnecting the airbag unit and plugging back in, see if the light goes away. If not disconnect again and connect up a resistor to it instead and see if the light goes out (Idon't know what the resistance should be or if its in a manual anywhere but you can buy a seet of different resistors for cheap or even a little box that can vary the resistance, like this thing, I got one which i justified by the fact i tend to fit aftermarket steering wheels in my cars and it makes it super easy to find out which resistor i need to get the light to go out).
If messing with resistors makes the light go out you can be certain its the airbag module thats at fault, either try find a replacement or just leave a resistor connected in there and not have an airbag. If the resistors dont work then you would have to start looking at the crash sensor and wiring.
 
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Oh, one last bit thought, if you connect to the ecu with MultiEcuScan or similar to interrogate it, disconnect the airbag before you connect to the ecu!!

When messing with the airbag module make sure your battery is disconnected, theres alot of scary stories out there about these things but if the battery is off it can't go off in your face, its against the laws of physics for it to off without a power source so don't fear.
 
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