Airbag fault light troubleshooting D9 406 HDI

Talk about the 406's electrical system, what wires do what, how to add extra functionality, etc.

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Airbag fault light troubleshooting D9 406 HDI

Post by crazy88 » Tue Dec 05, 2017 7:44 pm

Hi all,

Anyone here willing to provide me with some helpful advice on next steps to troubleshoot airbag faults on my D9 406 please?

The story so far;
airbags warning light and passenger airbag disarmed light permanently illuminated on the instrument cluster.
Messages: "passenger airbag neutrilized" followed by "airbag defective" message flash at startup on LCD display panel.

Scanning with PP2000 a global scan is reporting the airbag ecu has not replied, all the other ECUs respond to the global scan.

Other reported faults:

BSI: Permanent faults. Communication on wire DATA of the comfort VAN
Communication on the DATA wire of the air bag ECU
Communication on wire DATA with the rain sensor

Navigation ECU:
Intermittent fault. Input :. Reverse. Short circuit to positive. Contact always closed.
Remote intermittent fault. Vehicle speed signal absent or incorrect signal.

I've visually checked the multiplug for the airbag ecu under the center console for corrosion/damage as best I can after leaving the battery disconnected for a couple of hours and checked both plugs under the front seats for damage to no avail.

Any suggestions on next steps to trace the fault or how to get the airbag ecu to respond to give half a clue where the problem may lie please?

Thanks in advance.

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Re: Airbag fault light troubleshooting D9 406 HDI

Post by Doggy » Tue Dec 05, 2017 9:45 pm

Getting PP2k to talk to everything is sometimes a challenge. I normally try directly interrogating whichever ecu I'm interested in, but sometimes an ecu won't reply. Next I try the Global test, sometimes this will do the trick and establish comms. Failing that, I try going back to the direct approach and finally try getting there by function, e.g. heating & ventilation will involve typically the engine ecu, BSI & climate ecu's.

For no reason that makes any rational sense, one of these will normally work.....

You could have a dead airbag ecu, it's vulnerable to spilled drinks and the like where it is. Don't think they're coded in any way, try 'liberating' one from a scrappy.
2002 HDi 2.2 Exec Estate, (2008-12)
2003 HDi 2.2 6-speed Exec Estate (2012-19)
2009 Citroen C5 2.0 HDi VTR+ Estate

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