Volvo 850 driver's airbag open circuit troubleshooting

pgbuick · Post by **pgbuick** » 21 Jan 2012, 18:10

Moderator note...warning
Warning for all...do not use ohmmeter for checking airbag continuity. Current from an ohmmeter can fire the airbag. This is dangerous. Checking circuit continuity of car wiring with air bag disconnected as below is fine.

The SRS light in our 1993 850 is always on. The B5 code is 212, which is "Drivers Airbag Open Circuit". A while ago a Volvo garage who was doing some other work for me cleared the code and it came back shortly thereafter. The law here in Mass apparently has changed and cannot get an inspection sticker if the SRS light is on. So need to either fix it or disconnect the light.

I started at the steering wheel and, using one of the writeups here, took apart the whole assembly to inspect the clockspring assy. All looked OK in there. nothing broken. There are two wires coming thru the orange connector on the steering column to the airbag, one is solid orange and one is white with orange stripe. With the clockspring assy removed from the vehicle I checked the continuity of the assy. From the harness connector to the airbag connector I have good continuity (less than 1 ohm) on both wires, BUT there is also less than 1 ohm when cross checking. In other words, both ends of both wires show less than 1 ohm when checked to the other wire. My logic says that there is something completing the circuit between the two conductors within the assy as the ohm meter indicates, but I am unsure if this is normal, or if it indicates a bad clockspring assy.

If anyone is familiar with the airbag circuit logic I would greatly appreciate if you can share your thoughts on troubleshooting this circuit.
Thanks
Pat

Post by **rspi** » 22 Jan 2012, 20:27

I would replace the air bag with one from a salvage yard, have the code reset, and see what happens.

deeess · Post by **deeess** » 08 Apr 2014, 10:29

For anyone who finds this old post looking for info:

Look at the connector on the contact reel (not the airbag connector). There is likely a spring-loaded bar which shorts the connector when unplugged.

Post by **abscate** » 10 Apr 2014, 06:13

Warning for all...do not use ohmmeter for checking airbag continuity. Current from an ohmmeter can fire the airbag. This is dangerous.

93_850glt · Post by **93_850glt** » 11 Jun 2015, 21:00

I have a 93 850. I have the SRS light on and diag code of 2-1-2, which suggests open circuit on the driver side airbag. However, after replacing the crash sensor and removing the airbag, I tested for connectivity. I got 3 volts consistently across the leads to the airbag. I also tested 0 resistance between the crash sensor and the airbag leads on the steering wheel.

Finally, after resetting the code, the SRS light flashes on and off over a period of 10 seconds before staying on. So, why am I still getting the SRS light and code if I have connectivity and seemingly no failure in wiring? Should the airbag be seeing more then 3 volts? Where could the the voltage loss be occurring? Based on what I'm seeing, it seems like the airbag connectivity is perfectly fine and the SRS is reporting a false failure condition!

What do you guys think?

Post by **Ozark Lee** » 12 Jun 2015, 07:14

For the driver's side it would suggest a bad clockspring or perhaps a bad bag. Stick a 5 ohm resistor across the airbag socket and see if the code clears. If it does the airbag itself is bad.

...Lee

93_850glt · Post by **93_850glt** » 08 Jul 2015, 16:42

Thanks Ozark! I finally got around to testing this and the problem persists with the 5ohm @5w resistor I used. Could I use a jumper to connect certain pins on the crash sensor to bypass this? I'm not concerned with the airbag working, I'd just like to pass inspection.

Anything else that you think it could be?

Thanks again!!

Post by **Ozark Lee** » 08 Jul 2015, 17:58

The previously mentioned clockspring is the most likely culprit. While disabling the airbag isn't a great idea what you have now is a disabled SRS system. As I understand the system the entire SRS, short of the early implementation of the SIPS bags which a '93 doesn't have, is completely disabled if there is any error. The SIPS bags on the pre '99 models have their own independent igniter on the sides of the seat.

What you could do is add the resistor to the line leading into the clockspring and see if the error will clear then. The 5 Ohm resistor may be a bit big, I can't remember the exact resistance the system is looking for and it may need to be closer to 2 Ohms to satisfy the controller.

...Lee

Post by **abscate** » 09 Jul 2015, 04:36

I though the system sent an AC signal and one had to do more than just match the resistance of the airbag. I will research.