Can I check the airbag switch by bridging the plug connections?

My Airbag light is on , I've checked all the solutions mentioned connections under seat etc . I have looked at the switch at side of dash and it looks ok , it's very difficult to check it it's working though , as a very quick check ( in no way a permanent solution ) could I loop a small piece of wire and put either end in the two wire socket , I'm assuming that that's all the switch does? , Also I have heard conflicting info , people have stated light goes out when problem solved ( often saying light flashes on and off with bad connection) others have stated it needs resetting , could someone please clarify , thanks.

If any of the air bags have ever been "fired" the airbag ECU will need to be replaced or reset by nefarious means or the light will remain permanently on.

Other than that with the airbag system working correctly the light will go out as soon as all the components are correctly installed and serviceable. So, no it doesn't need to be reset.

If you are keen on diagnosing faults on your car and you have a spare laptop, I highly recommend getting a LEXIA scan tool. They are now cheaper than one trip to Citroen to get the faults scanned by them. You need to find out what the airbag module is complaining about before you can attempt a fix. It could be the clock spring in the COMMs unit, could be the accelerometer, could be anything!

To answer your question, no, the switch is a voltage divider. So the ECU can tell if the switch is faulty. If you have a multimeter you can check the resistance change when you go from airbag on to air bag off at the switch. I'm sorry I cant tell you the value but it wont be a short circuit or an open circuit. At best guess would be a couple of KiloOhms.

Thanks , if i buy a new Ecu from ebay (as cheap as £10!) can i put it directly in or does it need to be reprogrammed ? , Again I have heard conflicting information , Thanks.

Because there are different configurations of airbag set ups e.g with and without deactivation switch and with and without side curtain airbags ETC, you have to get the same configuration module as your cars module (or car, if you see what I mean). If you get a module not suitable for your car I.E. not configured the same, it might bring the light on or it might not work correctly in an accident. For example if you have curtain airbags but you get a module not configured for curtain air bags they might not be fired off in an accident. Or if you don't have curtain airbags but you get a module from a car with curtain airbags, that will bring the light on because it will go looking for airbags that aren't there.
Again, if you have a LEXIA you can just reconfigure the module.

Neilcmusic1 wrote: ↑Tue Feb 11, 2020 10:08 am Thanks , if i buy a new Ecu from ebay (as cheap as £10!) can i put it directly in or does it need to be reprogrammed ? , Again I have heard conflicting information , Thanks.

As Ozvtr has suggested, before starting to change components on a trial basis you'd be better off with some proper diagnostics. By changing components that may not be at fault you could be causing new problems that may complicate your error diagnosis.

As Ozvtr has also suggested, a working Lexia clone will help you with a proper diagnosis.

I would just like to query 1 last thing before I get this looked into further , I have removed the on/ off passenger air bag switch and connected the two switch pins to a loop connected to a LED and battery , when I put the key in and switch it either way the light stays on , does this mean the switch is faulty ?

Hang on! Which "air bag light" are you talking about?

Are you talking about the orange passenger side air bag deactivation light or the red air bag system fail light?

C3Car has just put up a post in the "tips and tricks" area. It shows the switch is a short in the on position and about 400 ohms in the off position.

When you pull the switch out of circuit, the orange light should go out and the red light should come on? The orange light stays on no matter what position the switch is in? Is that the case? If so then yes, your switch is faulty.

If you are talking about the red light then we are back to square one. Even if the switch is a short, it should only bring the deactivation light on. There is a still a problem elsewhere.

I'm sorry, my circuit diagram shows two resistors in the switch but C3Car's investigation shows otherwise. So what I said in a previous post about it not being a short was wrong.

Here in AUS it's illegal to have babies or children in the front seat, so we don't have the air bag deactivation switch.

The red airbag light and the passenger airbag warning are both on all of the time, whether I switch the deactivation switch on or off , im hoping it's switch problem , there certainly doesn't seem to be any problems with the connectors under the seats .

This is a photo of the 2 warnings that come on when the engine is turned on ... After the initial checks have run

What happens when you disconnect the switch? Does the passenger airbag light go out? I would still expect the air bag fail light to stay on.

No that's not right. With the switch in the on position it should be shorted and the light goes out. So if your switch is shorted then your light should go out?

This is not making any sense.

If the ECU thinks there is a fault in the switch why has it deactivated the passenger air bag? Some sort of fail safe? If in doubt deactivate? I would have designed it the other way around.

Your LED continuity tester might still work with the extra 400 ohm load? The switch might have some resistance but the checker still works. Perhaps there is resistance in the switch?

Did you try bridging the connections at the wiring loom (like you were originally going to do)? It's possible the switch is OK and there is a break in the wiring.