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#1620245 - 10/05/2018 00:15 Re: 20vt airbag light on - whats the usual reasons? [Re: mli]
GrahamL Offline
Forum is my job

Registered: 17/12/2005
Posts: 3530
Loc: Pothole City
Strange, there must be something more going on than the basics shown in the circuit diagrams, or the diagrams are wrong (wouldn't be the first time).

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#1620543 - 17/05/2018 16:53 Re: 20vt airbag light on - whats the usual reasons? [Re: mli]
mli Offline
Club member 717
Reaping the fruits

Registered: 02/10/2010
Posts: 68
Loc: Denmark
Hi Graham et al

Was busy with parties and work...

Yes I believe there is more to the LED circuit in the dashboard than diagram shows.
Probably something that requires specific voltage on the LED signal wire.
So if ECU short it or its open circuit then its lit.

This can be seen on some diagrams of other cars (Google).

I have a friend which has good electronic knowledge - we will try to work something out.

In the meantime I'm going to try a used unit from BBR! smile

I'll be back after playing around...

Cheers
M
_________________________
SprintBlue 20vt '97
Prev.:Coupe16v'94,Alfa156/33,MareaSW,2xPunto,2xUno

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#1620575 - 18/05/2018 13:01 Re: 20vt airbag light on - whats the usual reasons? [Re: mli]
DaveG Offline
Club member 311
Forum is my life

Registered: 16/12/2005
Posts: 6954
Loc: Lightwater, Surrey, UK
The wire for the CODE warning light is BG (white-yellow) from CODE box connector B pin 2 to connector A pin 7 on the instrument panel . The wire for the airbag light is S (pink) from airbag ECU connector pin 13 via connector 246 to CN (orange black) wire on connector E pin 6 on the instrument panel. That's according to the XII-96 update to the Instrument panel Connection diagram, but the later 1999 onwards diagram shows the same thing. So it looks like you have done that correctly.

If you just earth connector A pin 7 on the instrument panel, does the CODE light come on? If you earth connector E pin 6 on the instrument panel does the airbag light come on? You could try to use the ABS warning instead, the GV (yellow-green) wire from ABS ECU pin 21 to connector E pin 5)?
_________________________
1996 Portofino 20vt & 2000 Pearl White Plus
1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake

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#1621248 - 02/06/2018 09:08 Re: 20vt airbag light on - whats the usual reasons? [Re: mli]
mli Offline
Club member 717
Reaping the fruits

Registered: 02/10/2010
Posts: 68
Loc: Denmark
Hi All

Im a very happy man :-)
The car went through DK MOT today so now I have plates on it - ahhh...

A few notes:
. The instrument panel (flex PCB) IS made exactly as the diagram - only bulb w 12v supply and a wire to ECU!
(so the ECU are supposed to GND the wire a few sec after ignition on - probably with a transistor)
. My problem was a SHORT-CIRCUIT to GND in the *harness* or *connector* close Airbag ECU - this means power to bulb all the time - and probably the reason for ECU failure as well...
. I found this after checking resistance to GND on the lamp wire (1ohm ~=GND) - after disconnecting the E-plug on backside of instrument panel.
(note airbag lamp wire changes colour after conn 246 en-route to E-plug - from 'pinkish' to orange-black)
(note2: the ECU was disconnected all the time)

Fix:
. I then cut the lamp-wire close to ECU (luckily short to GND was closer to ECU than the cut :-)
. then I put a short wire from GND side of ABS-lamp to GND-side of Airbag-lamp (no transistor as bulbs are only 0.1mA load - maybe should add transistor in the long run)
So, Airbag light now follows ABS-light - good enough for MOT.

Next:
Now I can try to remove the short circuit from harness/connector.
Maybe I can then clear the 'ECU Failure' error that trw2scan detects from the airbag ECU?

Thanks for the support from all of you!
- and thanks for the effort by BBR...

Have a great weekend !
Cheers from sunny DK (25-30degC for 3+weeks now)
M
_________________________
SprintBlue 20vt '97
Prev.:Coupe16v'94,Alfa156/33,MareaSW,2xPunto,2xUno

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