Electrical - Fool Airbag Module - how to do it?

[SeptemberSquall]

Hi there,

In my car, there are side airbags in the driver and front passenger seat side bolsters. I am removing the seats to replace with aftermarket seats. Disconnection of the airbag module causes the computer to throw a code and warning light on dash is on. I need to construct a device to attach to the main loom in place of the airbag module to give the ECU the answer it is looking for and prevent it throwing a code.

The connection from main loom to side airbag harness is a simple two-wire plug. I had expected that the computer would just be listening for a specific resistance from the airbag module in the seat to determine that it is present and accounted for, but no such luck. Actually, with ignition on the computer seems to be 'interrogating' the airbag module with a variable-voltage signal (waveform from 0.0v to 0.11v, 4 sec approx wavelength'.

I remove grease pretty good but am about 3/10 on electrical questions. How do I:
1. work out what response the ECU is listening/interrogating for, and
2. construct a device out of resistors and diodes from Jaycar to 'trick' it?

Thanks in advance for any expert advice or even random speculation. Cheers!

[SeptemberSquall]

I have considered removing the airbag module from the original seat and connecting it to the loom, however this would involve destroying the original seat, which *must* be avoided.

[AAAAGZE]

buy a set of damaged seats and destroy those in your quest.

[2jzhilux]

What vehicle is it?

[convertableTA23]

Don't do it, you will void insurance and make your car unroadworthy. No engineer who is worth his weight in salt will mod plate those seats and removing a saftey device will make the car unroadworthy and void all insurance.

Finally if you do still want to do it i must assume you don't care about the safety aspect of the vehicle, leaving it unplugged will only affect the airbag system and bring on the airbag light. Pull dash out and remove bukb from instrument cluster.

But once again why would you???

[TERRA Operative]

Works Bell have a module that plugs in when you remove the airbag steering wheel. I've never played with one, but I assume it's just a resistor (it's a pretty small thing).
I would assume the voltage being sent is used to determine if something is there by measuring a resistance. You could try hooking up a potentiometer to the wires and adjusting the resistance until the light goes out.



*I take no responsibility for any inadvertently deployed airbags, do at your own risk etc etc.

[2jzhilux]

If its a toyota im pretty sure its just a 2.1ohm resistor.

[SeptemberSquall]

buy a set of damaged seats and destroy those in your quest.

Thanks, tried this, too scarce and hence too expensive. It's a brand new car.

[SeptemberSquall]

What vehicle is it?

2012 Suzuki Alto.

[SeptemberSquall]

Don't do it, you will void insurance and blah blah blah random parental-instruction rant etc etc why would you???

Thanks dad,,,
In this thread; HOW to do it, not WHY NOT to do it - okthxbai

[SeptemberSquall]

Works Bell have a module that plugs in when you remove the airbag steering wheel. I've never played with one, but I assume it's just a resistor (it's a pretty small thing).
I would assume the voltage being sent is used to determine if something is there by measuring a resistance. You could try hooking up a potentiometer to the wires and adjusting the resistance until the light goes out.

*I take no responsibility for any inadvertently deployed airbags, do at your own risk etc etc.

Thanks for your constructive post. I don't have a potentiometer, so tried testing the pins of the airbag module wire with a multimeter set to impedance mode, but could not detect a resistance. By this, I mean that when I touched the probes to the pins, I got 1.6 ohm, but when I touched the probes drectly to one another I also got a fluctuating reading arou d 1.6 ohms, as though that was the lowest impedance the multimeter would register. Hmm.

[SeptemberSquall]

Thanks all for your helpful suggestions so far. Will try getting a potentiometer and testing a variety of resistances to see if we can trick him into thinking his distended arms are still attached. Please keep the suggestions coming!

[cambelt]

Please don't check the resistance of any undeployed airbag as all multimeters induce voltage across there resistance functions . And maybe boom
Dave

[greywolf]

I don't believe he is putting voltage across the modules themselves, but across the wiring leading from the ECU.

[SeptemberSquall]

I tested for voltage on the lead from the car, which was a cycling voltage 0.0v-0.11v on a ~5sec clock cycle.

I also tested resistance on the airbag module, as I suspected that the body ECU was listening for a specific resistance from the airbag module and wanted to see if I could work out what that resistance was.

It didn't deploy, but I will keep your advice in mind! = )