Technical B0123-1B -Driver's abdominal pretensioner error

[Phelanpa]

Hi,

My Fiat 500 Lounge 2008 with 245k km / 152k miles has been going great. I've had it since new. However I am now being driven mad by an airbag error with periodic bleeping when I am driving. Got the multiecuscan out and I'm getting a B0123-1B error - Driver's abdominal pretensioner - Circuit resistance to(o) high/above threshold.

When I check the Airbag Unit parameters the Driver Side Airbag resistance it is sitting at 3.5 ohm and the Driver Pretensioner resistance is sitting at 3.0 ohm which seems to contradict the warning - I expect 2.5 - 3.0 ohm is acceptable. So why the error?

I dug a bit deeper and see in the error details it says:
Operating time: 87509 min
Battery voltage 8.0 V
Odomerter: KM
Passenger Airbag: Disabled
Passenger Airbag exclusion switch: Off
Failure Indicator light: On

I have also noticed that in the Airbag parameters the Voltage is not populating despite being selected - see screenshot below. On other modules the Voltage parameter is reported at 12v which is what I would expect.

Can anyone on the forum confirm the voltage should be displayed for the Airbag unit - but then I am wondering if there was an issue with power to this unit, surely I would be getting a whole heap of other warning messages and not just the one message about the Abdominal pretensioner?

Has anyone any ideas?
Do these pre-tensioners suddenly fail? I know the car has not been in a crash. I've have issues with other cars where the wires/connector under the seat have come loose/broken but all seems well on my Fiat 500 from what I can see.
I will pull the side panel off the back inside rear and check the wires around the pre-tensioner tomorrow night, but I'm looking for any advice from those out there in the know. I'm particularly interested in this 0 (zero) voltage on the parameters, and the reference to 8v in the error details. Is this a red herring, or does this need further investigation?

Thanks for any input you might give in advance. I've successfully fully maintained this car myself from new but this is a bit more puzzling than normal and I don't like to give in too easy - so I'm not heading for an auto-electrician just yet!!

 

[the green vanper]

Hello,

I'd start by adding another earth wire to the housing of the airbag module (a mount screw for example), could be directly from the battery for test purposes. The 8 V is strange and definitely too low. Be sure to disconnect the battery in a safe way everytime you play with the airbag module connections (and pretentionners, airbag connectors, too). Safe way means doors closed, central locking engaged (you can leave the window open to access the car easily if needed), let it settle for a minute or two (until the display on the speedo comes out).

Check the downloads section of the forum, I've uploaded a couple of days ago a set of earth / power supply docs, you could check both for the airbag module. Should be listed. Check the proper doc regarding the car options.

Here's also the Airbag system doc, however it's for the facelifting model (11/2008), don't have access for the moment for the previous one. I'll upload it once available.

 

[Phelanpa]

Thanks Green Vanper for those downloads.

I’m heading out to the garage now and will add a ground etc. wish me luck!!

 

[Phelanpa]

ok. I have good news the problem is fixed.

And I absolutely hate when people do not return to forums to share how they fixed an issue after they have looked for support and received it, so I’m sharing below details of what I did to fix it.

I was concerned about the low and missing voltage readings so I took the battery out and put it on a charger. I needed to fully disconnect the battery anyhow as I was going working on the airbag system, so taking the extra step to put it on a charger was easy.

Then I removed the bottom of the rear seat only - there is no need to take the seat back out. I unbolted the drivers seatbelt and got access to the pretensioner by taking the various panels off. I inspected this wiring all along from the pretensioner back to the airbag écu located under the heater. I only looked where wires were already exposed and did not remove any of the existing tape. There actually was very little wire exposed and tbh I did not spend too long on this as there was no sign of water ingress or much potential for the wires being disturbed or stressed. I did give the harness a good wiggle in the process but did not find anything obvious.

I then went to the airbag ÉCU - I have the old Metal casing ÉCU. I disconnected both plugs from the airbag écu visually checked them and they looked good. Then I saw the very thin earth wire coming from the loom and earthed to a small bolt located just behind the écu unit - so just 2 or 3 cm from the écu heading towards the gear stick. It was hard to see this bolt but it looked to be a bit cloudy « that’s the best word I can use to describe it. So I removed the nut and removed both the earths that were going to this and cleaned then - the connectors themselves were in good condition. I then made up an additional earth wire about 30 cm long. I put one of the original earth cables back on the bolt, then added my new earth wire before putting the second original wire back on it too. I put the nut on it, tightened it down with a m10 socket. I tethered the other end of my new earth wire as per the picture. I then put the battery back into the car, it had been charging for about an hour,

I started the car and the airbag warning light came on and the warning beeped. My heart sank. Then after about 15 seconds the light went out, and the warning has not reappeared I’m just back after driving somewhere for about 2 hours and all is good still!, Happy days.

The difficult part is I don’t know what actually fixed it, was it the wire wiggling, was it the additional cleaned earth, or has the battery disconnect or charge sorted it. However, a combination of all these may save someone in a similar situation in the future so there up you have it.

Happy 500 motoring.

Paul.

 

[Phelanpa]

So here are the pictures. If you have this error I’d recommend starting by examining the earth, and adding the extra wire - and as you are there, disconnect the battery first and charge it. Most likely the earth wire as suggested by Green Vanper (thanks again) sorted it so try that first.