Fiat Coupe Club UK

20vt airbag light on - whats the usual reasons?

Posted By: mli

20vt airbag light on - whats the usual reasons? - 02/05/2018 17:25

Hi All

My 20vt now have airbag light permanently on frown
(first time for me)
I tried a couple of searches on the forum but don't seem to find reasons.
Several notes on 'reset with PF' (which I guess means using some PC-tool or similar).
Then 1 note re 'replacing a spring'...

Any hints to reasons incl. the above?

(I need to fix it today or tomorrow frown )

I have an old Bluetooth OBD thingy - which should work with an App - havent tried really. Dont know if I can reset fault codes.
(note I'm quited trained in using the Peugeot 'PP-tool' wink )

Thanks!
M
Posted By: Heatseeker

Re: 20vt airbag light on - whats the usual reasons? - 02/05/2018 18:31

you need the Fiat/Lancia connector and something like startrek or multiecuscanner
Posted By: barnacle

Re: 20vt airbag light on - whats the usual reasons? - 02/05/2018 19:15

Startrek doesn't talk to the airbag; I *think* multiecuscanner works but you might need the paid version.
Posted By: DaveG

Re: 20vt airbag light on - whats the usual reasons? - 02/05/2018 22:36

Sykes ACR will talk using the ABS/Airbag pod (or MAP) but it could well be the "clock spring" which is as per this link (but note they have just sold out, so use part number or description "fiat coupe click spring" to find new or used) and a How To that shows how to get to it is here
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 04:29

Thanks guys.
In my cable drawer I found a 3-pin to OBD adapter and an OBD cable (hope its KL - used it for vw lupo).
So I'll install multiecuscan and try to clear error.

Thanks DaveG for guide to fix.
I don't think I can get parts in time, so hopefully clearing error is enough. But good to know fixing method...

Cheers,
M
Posted By: DaveG

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 05:51

I managed to clear the fault twice, including once for an MoT but eventually had to replace the clock spring. Good luck!
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 12:47

Hi Guys

A bit panic frown

I managed to get multiecuscan working with KL-cable and 3-pin adapter- can connect and read codes from ABS-unit.

But it can't find the airbag ECU...
I connect to a yellow cable below radio in center console.
There's also a 3-pin connector above feet in passenger/RH side (note its an LHD car) - no response here either...

Multiecuscan warns me when trying to connect to a TRW2 Airbag ECU - read on some sites that I should disconnect airbag first? arghh...

1. do you know exactly which connector to use ?
2. which module to use in multiecuscan? (TRW MY97? or TRW2).
3. did you disconnect airbag first (if so how?)

Thanks,
M
Posted By: DaveG

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 13:16

It should be the 3 pin connector under the radio, with a cable wrapped in a yellow sheath, so it sound like you have the correct cable. The other connector on the passenger side is for the ventilation system. There should be no need to disconnect the airbag - the connection is via the "clock spring" in the steering wheel (assuming it is this which has failed) - if you disconnect it, there will be a fault generated! rolleyes

Have a read of this thread - it might help?
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 14:40

@daveG: thanks !

Will read through other thread (strange I didnt find this)
Seems I should try TRW2scan...

Cheers,
M
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 19:17

Update:
I do have TRW2 airbag ECU 46306560.
So TRW2scan should work acc to other thread.

After failed attempts with trw2scan I realized from an alfa forum that one should use a settings file trw2.obd.
Now it can talk to ECU smile

Several Fault codes found - one of them 'low battery'
They were cleared an ignition off for 10sec. Ignition on: still airbag light on :-(
Read fault codes again - now different...
Cleared several times but no luck.

Needs some actual fixing it seems...

Cheers
M
Posted By: DaveG

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 19:28

Did any of the other faults that came up make any sense?
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 03/05/2018 20:05

Got actually only 2 faults "0x21" on mem location 0x02:
. ECU fault (0x01)
. Low battery voltage (0x20)

Second makes sense after standing without car battery.
This got cleared.

First one cant be cleared - comes back.
No more details on what's actually wrong with ECU.

......
First read:

Received ISO Code:
<0x55 0x45 0x80 0x0e 0x13 0x3b
Read ECU ID

<0x03 0x90 0x97 0x00 0x36 0x02 0x57
Read Fault at 0x02

<0x02 0xfd 0x21 0xde
Fault Description

Found error code 0x21 on address 0x02:
ECU fault
Low battery voltage

......
After clearing:

Received ISO Code:
<0x55 0x45 0x80 0x0e 0x13 0x3b
Read ECU ID

<0x03 0x90 0x97 0x00 0x36 0x02 0x57
Read Fault at 0x02

<0x02 0xfd 0x01 0xfe
Fault Description

Found error code 0x01 on address 0x02:
ECU fault
Posted By: DaveG

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 05:06

Hmmmm, time to get a replacement ECU I think?
Posted By: Blueboyracer

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 05:45

mli, I have a couple on the shelf.
Not sure if they will be compatible
One came off my Portofino 97 20vt but had an airbag fault I could not clear at that time
I will try and connect TRW2scan with the correct obd file (thanks for the tip) and see if I can clear the code
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 05:45

Yes. Looks like it.
But very hard to find in DK. And not many for sale elsewhere :-(
Fiat dealer checked for new ones in dk & part of eu - none. Part is obsolete - and so is the (newer) replacement part.
I just asked for dispensation re MOT - no way.

I have seen some offering reset of unit - might be worth trying.

Frustrating... frown

Cheers
M
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 05:47

Hi BBR

Sounds good :-)
Looking forward to hear news.


Cheers
M
Posted By: Jay1984

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 07:27

The actual ECU itself will sit right at the centre behind the dash. Easy enough to see it from the driver side footwell area (although, may be Passenger side if a LHD car). It's a yellow box and you should see the serial number on top of the box. If you post that number here, someone will hopefully have a working spare. Very easy to swap over (just disconnect the battery before you start).
Posted By: Anonymous

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 07:30

You could disconnect the airbag ECU to get rid of the warning light, that may or may not get you through the MOT.

Or if the light has to come on and go off you could connect it to one of the other dash lights like the key code light. That would probably be the easiest short term solution as the output for the key code light is available at the yellow code box above fuse box, would just be a case of running a link wire from there to the correct pin on the (unplugged) airbag ECU connector.

With an ECU fault the airbags won't fire in an accident anyway so you'd be losing nothing by disconnecting the ECU.
Posted By: DaveG

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 07:45

The other thing that might work trying to "reset" the ECU by just disconnecting the battery for a while, this often works for CODE problems. I have seen however that allowing the battery to die can corrupt the EEPROM in the CODE ECU, perhaps the same has happened here in the Airbag ECU, since you have had that "low battery voltage" error?
Posted By: Dazvr6

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 10:09

I replaced the airbag ECU on my coupe with a used replacement from this guy at Autosportivo (UK)
No problems since then:

Airbag ECU
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 04/05/2018 20:03

Hi guys

Lovely to get all this response smile

@jay: i have located and connected - see # above. Hopefully BBR will have a working one smile

@graham: Disconnect: the DK MOT will check for on&off. evil
Tie to other light: I have been thinking along these lines as well. But due to prep for big party tomorrow didn't have time to play with it.
About loosing nothing: I got a garage to quickly test ECU as well - he said most 15+ year old airbag will only give a small puff anyway (don't if it's true).

@Dave: Actually I did try this last night... No effect. My old battery exploded on me some months ago - might be at this time EEPROM got corrupted? Or a bit earlier when it ran completely flat? Who knows.

@dazvr6: thanks - now I'm hoping for good news from BBR. Otherwise I'll do the wire trick.
Posted By: Blueboyracer

Re: 20vt airbag light on - whats the usual reasons? - 05/05/2018 05:23

I’m going to try anyway mil, but I suspect I have the wrong cable as I have been reading Downhillryder post again.
Posted By: Blueboyracer

Re: 20vt airbag light on - whats the usual reasons? - 05/05/2018 10:20

Sorry mli
One of my Ecus is not responding
The other won't let my registered multieuscan clear the codes
I believe the cable I have is not fdti and therefore won't work with rw2scan
Sorry
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 05/05/2018 20:37

Hi BBR

thanks for trying.
Maybe you could send best of them to me for playing around?
PM on this?

FYI (all in thread):
I promised my daughter to give a ride today in the coup w her friends (special day).
Managed to do this w/o MOT (stretching the rules).

Thanks for support.
Cheers
M
Posted By: Blueboyracer

Re: 20vt airbag light on - whats the usual reasons? - 06/05/2018 06:46

PM sent
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 08/05/2018 20:12

@graham: tried today to 'drive' it with code lamp wire.
Not working. (Result was both light up)
Actually airbag light is still on even when ECU and airbag is disconnected... A bit spooky.

Going to try with abs light. But I couldn't find conn 155 today (shoukd be around RH door hinge) evil

Cheers
M
Posted By: Anonymous

Re: 20vt airbag light on - whats the usual reasons? - 09/05/2018 06:55

Did you have the airbag connector unplugged but the code box connector still plugged in when the wires were connecting the two?
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 09/05/2018 13:11

No.
I disconnected battery - then the airbag and then the ECU (plug off).
Then I reconnected battery.

Blimey, I just realize I still have passenger airbag connected on the wires - hmmm - but as I read wiring diagram then there should be no power to the passenger airbag with ECU disconnected.

Cheers
M
Posted By: Anonymous

Re: 20vt airbag light on - whats the usual reasons? - 09/05/2018 14:09

The code ECU plug would need to be plugged into the code ECU to control the code light and airbag light with the link wire. Just have the airbag ECU plug unplugged.
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 09/05/2018 19:31

Sorry maybe a bit cryptic writing.

I had airbag disconnected (wheel airbag)
I had airbag ECU disconnected (plug out)
I had code ECU connected normally.
I then had a link wire from code light wire on code ECU (white-yellow) - to the airbag light wire on the airbag ECU plug (pink).
But it meant that code light (also) stayed on...

Cheers
M
Posted By: Anonymous

Re: 20vt airbag light on - whats the usual reasons? - 09/05/2018 22:15

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).
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 17/05/2018 14:53

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
Posted By: DaveG

Re: 20vt airbag light on - whats the usual reasons? - 18/05/2018 11:01

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)?
Posted By: mli

Re: 20vt airbag light on - whats the usual reasons? - 02/06/2018 07:08

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
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