Hi all, 

Have a problem with an airbag light and wondering if anyone could shed some light on it for me. On a scan it shows me B0004 drivers knee bolster circuit resistance below threshold. Looking on live data it shows at 0.8 ohms what I suspect is very low, if I fit an airbag resistor it brings the resistance up and the code will clear indicating the wiring etc must be ok. The problem I have is that I have had two airbags from ford (main dealer) both looking like they have been opened and fitted previously and on installation they both read simular low resistance of around 06./0.8 ohms and brings the light on.

The chances of having two faulty from main dealer is slim but looking like they have been fitted before i strongly question it. Does anyone know if they are ament to be low from standard and I could be looking at a software issue or something or should they read more like 2.5-5omhs ish and I am getting supplied faulty ones. 

Thank you, Adam.

Hi Adam, the quick answer is "I don't know" but .....

Firstly if you think the new air bags may have been fitted before then you should not accept them.

Many years ago now (about 15years) I actually made some testers for a major air bag manufacturer to check the resistance. It was a switched resistance box and went from 0.01 ohms to 2.4 ohms. The trouble is I can't remember what the other 4 resistance values were.

can you measure the resistance of any other air bags on your vehicle ? They must all operate in the same resistance window. I do kind of think you will find them all to be around 0.8 ohms, which will mean you have a controller fault.

 

Thank you for the reply much appreciated.

I have requested for then to take them back as I do not want them and obviously don't want to order a third until I have been credited for these two.

As for the other resistances looking on data they are all around the 3.5omh with the drivers knee being the low one to cause the error code.

1 hour ago, AfordM said:

they are all around the 3.5omh

Hi Adam, it would be reasonable to expect that all the airbags in your vehicle will use the same base line for resistance. Therefore it would seem that 3.5ohms is the nominal value for a correctly operating airbag in your car.

did you ever get to the bottom of the problem we have the same issue

19 minutes ago, leeroy666 said:

did you ever get to the bottom

You are not going to get an answer.