Resetting service warning lights

[The Other Mike]

Would love to know how anyone would actually perform this action

The built in precautions to prevent accidental deployment of an airbag also ensure intentional deployment

[The Other Mike]

The airbag light sequences for each car are published. Requiring an engine start to extinguish an airbag light would IME not be a valid sequence.

[dennis]

Well that is a stupid claim, care to back it up?

[The Other Mike]

I suppose the specific warnings in car manufacturers own service literature for the past 30+ years stating similar precautions before woring on any part of the airbag system are invalid too?

[The Other Mike]

Almost certainly the case with aftermarket low cost diagnostics.

Pre-OBD it sometimes required another specific manufacturer plug in data cartridge that only covered the airbag function and nothing else.

This used the same basic handheld diagnostic device as used for the engine still plugged into the same vehicle diagnostic socket using a shared pin on the same vehicle bus with each control unit responding to a specific poll. .

[dennis]

You may note that it includes the terms that it is dangerous to you or anyone else. This includes things like faulty safety systems like brakes and airbags. Only a part of a system has to be faulty to be unroadworthy, like the warning lights being on or not working.

[Harry Bloomfield]

Peter Hill used his keyboard to write :

I was responding to the manufactures original suggestion of the need to replace them after ten years, rather than after deployment. Nobody stocks them, even for new cars - so far as I am aware and the latest advice is that they have an unlimited installed life anyway.

[Harry Bloomfield]

The Other Mike brought next idea :

None the less - I understand that doing such resets the warning light on my car, not that I have ever needed to. It will be recorded in the SRS ECU though, as a fault.

Usual fault is moisture getting into the floor mounted ECU, replacement of which requires coding and poor connections to the seat / head airbags, due to movement of the electric seats.

[Harry Bloomfield]

True of most of them. Mine needs separate systems for OBD, SRS, FBH, ABS and etc..

[Harry Bloomfield]

Dave Plowman (News) laid this down on his screen :

It is quite feasible to have them capable after much longer than 30 minutes, but they design them to be discharged within 30 minutes to be safe. An airbag being triggered can do some serious injury.

[Harry Bloomfield]

Fredxx explained :

I don't know how the FB deal with the risk, mine has steering wheel, A post, B post and more in the side sides. I have in mind an image of me and car bouncing down the road is they should ever deploy.

[Harry Bloomfield]

The Other Mike formulated the question :

In my own experience, manufacturers play very safe with such instructions, rather than risk someone being hit in the face by a deploying bag. Likely five minutes wait would be enough for it to be safe, but why take the risk?

[Roger Hayter]

That section relates to selling a vehicle. You want section 42 of the same act which makes it an offence to drive a care which fails to meet

*any* particular one of the construction and use regulations. But you still need to prove (rather than merely assert) that the failure of a airbag warning light amounts to a breach of the construction and use regulations. I agree it is quite likely, but that would not be sufficient basis for prosecution until the relevant clause in the regs is found.

[Dave Plowman (News)]

Just querying the half hour. Because for a start it will invariably change from car to car. So I'd guess a figure plucked from the air.

[MrCheerful]

or a dog chewing through the wires under the seat (been there and soldered the remains to fix it.)

[Dave Plowman (News)]

The are also possibly backup batteries in some parts of some cars. But that's not to say they will feed the airbag trigger mechanism. Which I'd guess will need a fair bit of current.

But if you disconnect the battery at the start, chances are it will be fine by the time you've actually got to the airbag to unplug it.

[Dave Plowman (News)]

A minute after disconnecting the battery seems far more likely to me.

And it's going to take more than a minute to put down the tools used to disconnect the battery and pick up those needed to remove the airbag. ;-)

[Dave Plowman (News)]

Can you explain why you'd need an airbag to work some 30 minutes or more after a car has totally lost power in an accident, etc?

Any form of electrical storage costs money. And the bigger that store, the more it costs. Car makers are well known for not spending a penny where a farthing will do.

[Tim+]

It?s hard to conceive of any reason why you would want airbags powered for so long, and easy to think of reasons why this would be a bad idea. Seems far more likely to me that the capacitor will be designed to discharge via a resistor over a much shorter period (less than a minute I?ll wager).

Tim

[dennis]

Are you going to disconnect the only thing that will supply current after a few seconds, the battery?