Airbag resistance values after replacement

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sigi
Posts: 7
Joined: Sat Apr 06, 2019 6:04 pm
Vehicle: Fiesta MK7

Airbag resistance values after replacement

Post by sigi » Sun Apr 28, 2019 2:56 pm

Hi All !

After a crash all 3 Front Airbags were deployed including belt pre-tensioners locked.
I replaced Driver and Passenger Airbag and both belt pre-tensioners now, and waiting for the knee Airbag (but still did not reset the RCM).
Now with ForScan I meanwhile observed the Resistance of the replaced modules, but it doesn't look like I would have expected it:

Driver-Airbag 0 Ohm
Passenger Airbag 0 Ohm
belt pre-tensioners Driver 0 Ohm
belt pre-tensioners passenger 0 Ohm

Side Airbag Driver 2-3Ohm
Side Airbag Passenger 2-3Ohm

From you experience - is it possible that those airbags are just not shown by RCM since they were deployed and it is currently locked ?
Or did I just have the coincidence to buy 4 crap parts ?

Regards
Sigi

denbo
Posts: 590
Joined: Mon Feb 06, 2017 3:00 pm
Vehicle: ford focus 16 zetec

Re: Airbag resistance values after replacement

Post by denbo » Sun Apr 28, 2019 6:55 pm

Get the multi meter out and check the resistance your self. 2.3 ohm looks correct. Wait for the other parts to arrive and clear the crash data and they may come back.

sigi
Posts: 7
Joined: Sat Apr 06, 2019 6:04 pm
Vehicle: Fiesta MK7

Re: Airbag resistance values after replacement

Post by sigi » Tue Apr 30, 2019 3:47 am

That is what I did now at least on the belt pre-tensioners, and I can measure 0.6 Ohm directly on the socket.
when I measure one of the deployed Airbags, I get almost the same resistance.
It seems Forscan only shows Integer numbers, so everything below 1 is displayed as 0.

sigi
Posts: 7
Joined: Sat Apr 06, 2019 6:04 pm
Vehicle: Fiesta MK7

Re: Airbag resistance values after replacement

Post by sigi » Thu May 30, 2019 10:52 am

I took some time, but here is the summary:

Astonishing , even if the belt pretensioners are showing a low resistance (0.9 Ohms) they are accepted by the RCM as ok ! :o
After I did reset the crash flag (bench method) all DTC's disappeared, no Airbag light anymore. :mrgreen:
So the lessons learned are that the resistance of the coil may be much lower then the 3 Ohms but still good . :idea:
Maybe also the RCM's check current is AC and the impedance shall be 3 Ohms (my multimeter just measures resistance) :?:

Btw:
If someone wants to do the bench method, this guys here are very helpful: :lol:
https://www.digital-kaos.co.uk/forums/

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