Technical Airbag light cant turn off

[Mickit]

Hi,

Background:
- Bought a Fiat Qubo with a handicap passenger seat installed. (Airbag, seatbelt wires etc. were not used, just laying under the seat)
- Replaced the seat with an original from a another Qubo (plugged in airbag, seatbelt wires etc.)
- Now I have an error light on the passenger airbag

Solutions i have tried:
- Went to a garage who had a tester/reader
- They were not able to turn off the airbag light
- If we unplugged the airbag cable from the seat, the warning light goes off.
- With the tester he could read the ohm resistance on the airbag unit. As soon as the wires were plugged in, it read to low resistance, and gave the error.
- Unplugging the wires, and the tester read normal resistance, and no error

Thoughts from the mechanic:
- He thinks the company who installed the handicap seat, has done modifications to the airbag ecu, so it thinks something is plugged in, even if its not
- Or there could be soldered in a resistance somewhere on the harness to the airbag/seat

The mechanic was not able to do changes to the ECU with his tester.

Do anyone have any suggestions/experience how to look even further into this? And how one could modify the airbag controller/ECU again, so it sees the airbag resistance correct.

All ideas are welcome, would love to have the airbag plugged in, with no errors! I will try and look through the harness, but i need to disassemble a bit...

Hope someone can help me further

 

[bugsymike]

On my daughters 2012 Punto Evo, previous owner had tried to repair the passenger seat sensor and shorted the BCM (body computer) Genuine Fiat part was around £140 odd for sensor, I got a Chinese basic seat sensor (£6)and soldered in the old resister from the damaged seat sensor as the chinese one had no sensor, I then had to replace the damaged BCM (new £149 eBay), finally I had to use my friends Snap On diagnostic tool to run a program called "proxi alignment" this basically checks what is connected to the air bag system and then tells it to "talk" to the BCM, everything was good after then deleting any old error codes etc. Hopefully you just have to run the proxi alignment program.
I understand many on Forum use MES tool which is more Fiat based to do the same job, so other members can advise.

 

[Mickit]

It might be that the proxi alignment program could be enough. I must see if i can find someone with access to MES in Denmark.

But might as well check all the wiring first to see, if anything has been soldered on somewhere.
Anyone know how/where the airbag wiring harness is running in the Qubo passenger side?

 

[bugsymike]

It doesn't have to be MES, a good garage diagnostic equipment such as I used , the Snap On Zeus can run the "proxi alignment program".
Be wary of shorting any wires as I think the previous owners poor repair of the seat sensor is what caused the BCM to fail! It needs the Ohms of the resister to protect the ABS circuit from overload/short.

 

[Mickit]

It doesn't have to be MES, a good garage diagnostic equipment such as I used , the Snap On Zeus can run the "proxi alignment program".
Be wary of shorting any wires as I think the previous owners poor repair of the seat sensor is what caused the BCM to fail! It needs the Ohms of the resister to protect the ABS circuit from overload/short.

Sadly i dont have a "friendly" garage nearby, where i can borrow and play with their diagnostic tool.

Now considering buying a OBDLink MX+ and the Multiscan iPad app, to just be able to do it myself.
Guess i can always sell the OBD adapter again, or help other people around me with their Fiat

 

[bugsymike]

If you check in the MES section of Fiat Forum you may find some near to you who has it.

 

[Mickit]

Solved! Followed the cable from the airbag connector. Under the carpet in front of the passenger seat, there was 7 cm of electrical tape in a different colour, than the rest. Removed it, and in there, voila. A resistor soldered in between two wires.

Cut it off with small pliers, new electrical tape in each wire, and then new around the whole bunch after.

Airbag error gone!

 

[bugsymike]

Yes , that makes sense, if the previous owner had had a non standard seat with no airbag system / seat sensor connected then having a resistor in the circuit made the BCM think it was connected but seat not occupied, so when you reconnected it then it probably had two lots of resistors in the circuit. As I mentioned on my daughters car I replaced the previous owners damaged seat sensor with a cheap basic sensor but had to fit the resistor from the damaged seat sensor to activate. In your case you were fortunate that there was no damage to the BCM.