T4 and Identifying airbag fault

[RoryRover]

I have the dreaded airbag light on and have tried the recommended first steps ( checking underseat wires and re-setting the ECU) but without sucess.

Rather than casting around in the dark, I would like to find out exactly what and where the fault is.

Is this something that can be identified by a T4 session ?

[marinabrian]

Originally Posted by RoryRover

I have the dreaded airbag light on and have tried the recommended first steps ( checking underseat wires and re-setting the ECU) but without sucess.

Rather than casting around in the dark, I would like to find out exactly what and where the fault is.

Is this something that can be identified by a T4 session ?

Without a shadow of a doubt, BigRuss is your man I'd say.
Brian

[BigRuss]

T4 will normally tell you on which airbag circuit the fault lies so at least you know where to start looking

It will also give you a list of connector numbers to check, connector pin no's and even the wiring colour codes.

There are specific faults however (eg. stored crash data) that it will pinpoint to an exact cause.

Russ

[rik007]

Hi, bit of a barge in on this one .. but a question on the back of this thread if I may...

I'm still stuck with the airbag light on and I cant yet find an solution. The 5amp fuse keeps blowing everytime I switch on the ignition. Clearly there is a short somewhere. After a reccoemend; I took the drivers door off and looked at the loom but no joy. I've also repalced the yellow connectors under the seats so I know its not that.

Can a T4 also help me detected where the short might be? Or is it a case of looking for the 'needle in a haystack'?

Next job is to take out the seats, remove the console, remove the carpet and poke around. But am loathed to do that if a T4 could pinpoint it.

Thanks, Rich.

[Mike Noc]

I'm sure Russ or Brian will put me right, but I can't see a T4 helping you here as you can't get the circuit powered up.

With a non safety circuit, as has been mentioned before, if you wire a bulb into the circuit in place of the fuse with a short it will light up.
Then start unplugging connections until the bulb goes out and you have found the short circuit.

With the airbag circuit though I wouldn't start unplugging things with it powered up. But maybe you could power it down each time and leave it for 10 minutes. Then disconnect one plug at a time and power it back up?

Might point you in the right direction and save some dismantling.

Mike

[rik007]

Originally Posted by Mike Noc

I'm sure Russ or Brian will put me right, but I can't see a T4 helping you here as you can't get the circuit powered up.

With a non safety circuit, as has been mentioned before, if you wire a bulb into the circuit in place of the fuse with a short it will light up.
Then start unplugging connections until the bulb goes out and you have found the short circuit.

With the airbag circuit though I wouldn't start unplugging things with it powered up. But maybe you could power it down each time and leave it for 10 minutes. Then disconnect one plug at a time and power it back up?

Might point you in the right direction and save some dismantling.

Mike

Thanks Mike, just so I've got it ... its OK to wire in a bulb in place of the fuse as this takes the load on the shorted circuit? i.e. Im not going to drain the battery immediately or set fire to the car at the place where the short is. Errm it might help me find the blasted thing if it did though! Looks like its a carpet out jobbie then and a 12v bulb.

Cheers, Rich.

[Mike Noc]

Yes, but it is only a momentary test just to check if the bulb is lit or not. Never done this on the SRS circuit but have done it a few times on other circuits.

Mike

[safety sweep]

Rik 007

I had a similar problem and found the fault was the connector under the passenger seat, having removed the one under the drivers seat I used this to replace the other no problem since.

[chrissyboy]

have a look between the seats where you buckle the seat belt up to .if one is longer than the other then they would have been deployed at some point thus storing crash data that will need to be cleared ,that will be the only way to put light out and of course placing the pre tensioners .if they are the same size then the yellow connector may have dirty contacts and just need a good clean .what ever you do dont start putting wires and bulbs to this circuit

[rik007]

Originally Posted by chrissyboy

have a look between the seats where you buckle the seat belt up to .if one is longer than the other then they would have been deployed at some point thus storing crash data that will need to be cleared ,that will be the only way to put light out and of course placing the pre tensioners .if they are the same size then the yellow connector may have dirty contacts and just need a good clean .what ever you do dont start putting wires and bulbs to this circuit

OK so what I am hearing is .. if the pre-tensioners have been used the light will always come on until they have been a)replaced and b)crash data cleared.

From what I've seen I dont think they have deployed, but I'll double check. I'll try and find a photo somewhere on the interweb of a normal length buckle.

I have replaced the yellow connectors already and that didnt cure the prob. But perhaps a good test is to remove the seats or at least unplg them and see if the fuse still blows.

Hmmm the bulb idea did seem like a way forward as it would I assume simply have privided a working resistance. But perhaps it could allow more than 5amps to flow. May be also the AirBag circuit is sensetive to current flow.

5amps at 12volts = 60watts .... I think ? i.e. IxV=W ... so I assume a 10watt buld would have drawn about 1amp, way less than the blow rating of the fuse.

But there again with a short circuit perhaps its a bad idea on the satey system. Just means buying a big bag of 5amp fuses until I find the answer! Hey ho.

Thnaks for all the input though.

Rich.