Resetting service warning lights

Correct. I was talking about "honest" john.

Want to post a link to one that says 30 minutes?

I would sincerely hope the designers have enough sense to put high value bleeder resistors across any significant capacitive elements to drain any residual charge within 2 minutes.

Its faulty, the light is/has been on, so what you just said doesn't apply or even make sense. That is the whole point, you do not have a clue as to what will happen when the system has/is indicating a fault. It may fail to go off when it should, it may go off at some random point, it may even work as expected. Clearing the warning doesn't make it safe unless it also passes the tests, ie. its unsafe and therefore illegal under UK law. Its just as illegal as havining spiky bits of metal sticking out of a car.

It's not that simple, Dave. Modern electronic modules and CPUs are made to be so energy-saving it results in as much high-impedance circuitry as possible, so even relatively small capacitances can take an age to discharge unless the designers have provided bleeder resistors.

True but that isn't a service warning light, its a fault indicator that requires service.

dennis@home explained on 28/04/2018 :

It is technically possible to enable them to still fire days later, it is also possible to have them still able to fire at 29 minutes later, but not at 30 minutes later.

Why don't you tell us, since you're such an expert?

The manual for mine (not a Volvo) states to leave it for 5 minutes after disconnecting the battery. And they've probably added a couple of extra minutes to get to this figure just to be on the safe side.

Given that its acceptable to disable an airbag (say when you have an infant in a read facing seat on the passenger seat), then I would be surprised if driving with a non functional airbag is actually an offence.

I would expect any safety critical design to fail safe...

For example I had a dodgy sensor on one car with ABS. If you hit a pothole with the rear offside wheel it would cause the ABS warning light to come on. At that point the ABS system as a whole was then inhibited, and the breaking system reverted to a normal non ABS one. A design decision, that elected to possible disable the breaks entirely on detection of a fault, would hopefully not get through a design review!

You're welcome.

Including the device which fires off the airbag?

And if a maker manages to design something which takes less current, they'll save money on the reservoir caps too, as they don't need to be so big.

No, you have to go to the local scrap-yard and buy a ten year old seat with the side airbag and the seat-belt pre-tensioner for £20, and then get someone to clear the 'airbag has been detonated' setting in the ECU. And wonder why the French don't have the Secondary Restraint system check if the primary restraint system is not in use because there is no passenger.

It's clear you haven't got a clue about how an airbag operates, how its triggering mechanisms are monitored, how faults are reported and, well lets face it everything about airbags.

"the airbag control system is designed to remain operational for up to

It's dennis, what did you expect?

No, it's 20 seconds for one of our current fleet where I have immediate access to the manuals (Lotus Elise S2)

There are a whole series of actions to be taken before any work around the steering wheel amounting to 18 pages in the manual.