Fiat Coupe Club UK

Airbag reset with 2 wires for diagnostic?

Posted By: Anonymous

Airbag reset with 2 wires for diagnostic? - 16/09/2014 13:40

Hi

I have tried searching how to reset my airbag light but the threads are quite old and seem to refer to the system with 3 wires going to the diagnostic port.

What do I need and where can I get software and cables to reset my airbag where there are only two wires to the diagnostic port?

Thank you
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 20/02/2015 13:55

I too need to reset my airbag light and have been trying to make sense of all the various threads on how to do it.

The simple "non answer" is to get a cable to connect a laptop to the airbag ecu and run one of "fiatecuscan" or "multiecuscan" or "trw2scan" and depending on the model of airbag ecu you have one of these should be capable of resetting it.

I found details of the cables required in this thread CLICKY

So I ordered this LEAD

I've located and download versions of each of the mentioned software and I am just waiting for the leads to be delivered. I'll update on how I get on with the software.

However while waiting I've been thinking - dangerous I know...

It's just a USB cable at the end of the day. Those flyleads surely don't feed power back to the computer so do they they suppy power to the 3 pin ecu connector ? I don't believe they would so I assume they are not really necessary - anyone know ?

Further as there are only 3 connector pins on the ecu plug why cant I just get an old USB cable and connect the right conductors directly to the ecu connector ? I don't supose anyone knows which USB pins end up on the ecu connector ?

Obviously when my cables arrive and I can test them and determine the answer. But I'm curious now.
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 20/02/2015 14:12

It's not just a USB cable, it also has an interface with a microcontroller and voltage conversion hardware built in, it just talks to the PC end via USB.

The +12v power connection is required to power the interface hardware, without that it won't work at all as the 3 pin socket in the car doesn't supply power. A full OBD socket does supply power to the interface, hence why the power connectors are only on the 3 pin adapter part and not on the OBD plug itself.
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 20/02/2015 14:25

Oh OK so that's not just an ordinary black socket it has electronics in it. Good job I never pretended to know anything !!!

Thanks Graham.
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 20/02/2015 14:36

Correct, that's why the blue bit with "VAG KKL" on it is so big, it has a small PCB in there.
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 27/02/2015 12:33

Finally gathered together all the cables etc but still having problems connecting to the airbag ecu. Fairly sure programs and drivers are ok as the KKL utility supplied with the cable scans and identifies the Com port. Multiscan and Fiatscan won't connect to the ecu.

I know from reading other threads that the climate ecu connector is in the same location so I need to determine if I am indeed connected to the airbag ecu but I can't find a second connector.

What I have is a yellow sheathed cable leaving the box mounted on the tunnel behind the console. This cable crosses the tunnel and splits into 3.

One branch goes to what I am assuming is the airbag ecu port. It has a 3 pin plug and a black and a white wire going into it. Another branch has two black wires (still sheathed in yellow) which disapears back into and under the tunnel. The third branch (too well covered to ascertain the internal wires) goes up towards the console and dash.)

Can I assume at least I have the right connector for the airbag ecu or should I track those other branches for another connector plug ??

Thanks guys
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 27/02/2015 12:51

Airbag connectors/cables are all yellow-sheathed. You're in the right place.
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 27/02/2015 16:39

Frustrating afternoon trying to get any software to talk to the ecu. Beginning to think I have "that" version of airbag ecu that nothing will talk too.

Tomorrow will try Startrek on the engine ecu in order to verify cables and setup.

I just want that damn light out !
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 27/02/2015 16:40

If multiecuscan won't connect then try trw2scan.

Or try connecting to the engine ECU to verify the cables and driver installation are OK.
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 28/02/2015 09:15

I've done this on my coupe once and a couple of times for Brian (forum name Rosso) who's had coops with both airbag ECU types.
Might be some useful details in my post here.

Two important points:
1) VAG COM KKL interface cable must have FTDI chip inside to work with trw2scan.
2) It might be necessary to link together ground pins 4 & 5 in the OBDII connector. My cables do not work without this modification (simple to test by inserting a bit of bare wire).

Sometime next month I'll be driving down from Scotland to JBT's in Shepshed. If you're located anywhere in-between I'd be happy to do a detour, bring my cables and do an airbag reset or two.
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 28/02/2015 16:22

That's a very kind offer Barney but I'm well south of London. Thank you though.

I've made progress of sorts. When installing the cables I have been unable to force the FTDI drivers on them , they want to use CH340 !

That aside I managed to connect to the engine ECU using Star trek, although it can be intermittent. Star trek tells me the immobiliser isn't connected to the ECU. I found a thread where Barnacle suggests a solution to that one.

I can connect to the engine ECU using Multiecuscan and it gives me the same ECU id as Star trek , so some progress.

Incidently I read in the Star trek source code that the Bosch ECU connects at 4800 baud does this mean the com port should be set to 4800 ? One for Barnacle ?

However I still can't connect to the airbag ecu. Multiscan offers two airbag modules TRW2 won't connect and TRW gives a "worrying" warning about using resistors on the squib. Can I try this one ???

I tried the TRW2 program but it tells me there are no connected FTDI devices. So I presume I need to find a cable with the FTDI chip set. Reading the FTDI documentation it seems you can force the drivers by editing the .inf files and setting the Vid/Pid numbers. I might try this.

I also need to try connecting those two pins.

The thread Barney linked to was a great help, but no definitive reset yet. All ideas will be tried with gusto !!!
Posted By: Rudidudi

Re: Airbag reset with 2 wires for diagnostic? - 28/02/2015 17:03

Ive a acr code reader that should clear codes, sw london
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 28/02/2015 20:41

If it's a CH340 you'll have no luck with trw2scan. FTDI drivers won't support it even if you change the id numbers.
I think changing id relates to customisation for manufacturers who use FTDI chips in their products. It allows them to put their own unique company and product numbers in but the chip and driver remain the same.
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 28/02/2015 21:54

The startrek code sets the baud rate internally. However it relies on some low-level driver (an initialisation at 5 baud) which is not supported reliably on non-FTDI chips.

For 16V, it needs an obscure baud rate - 7812.5 - which is, again, not supported by non-FTDI chips.

There are a lot of fake FTDI and Broadcom chips out there which implement the basic protocols but not the fine details.
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 01/03/2015 14:13

Rudidudi - that's a great offer. Thanks. I have just ordered a cable that uses the FTDI chip set. If that doesn't work I'll get in touch to sort something.
Posted By: Rudidudi

Re: Airbag reset with 2 wires for diagnostic? - 01/03/2015 17:08

Also worth trying multiecuscan or whatever it is called now, that also shifts codes

I havent found any one system to be 100% reliable in clearing codes, i once had to replace the ecu. They are cheap as chips though...
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 02/03/2015 12:32

Just out of interest - does anyone know what happens if you use MultiEcuScan to connect to the TRW2 airbag module. It gives a warning saying to "Disconnect the squibs and insert simulation resistors before continuing"

It's like a red rag to a bull , I want to try it !!!! Do the airbags go bang ??

Just curious whilst awaiting my cable.
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 02/03/2015 12:45

You're talking to an ECU that controls explosives. The software includes actuator tests...

You work it out!
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 02/03/2015 14:32

Yes I guessed it might go bang at some point but the MultiEcuScan software gives this warning BEFORE it connects to the airbag ecu.

I wondered if it would connect safely but go bang when you tried to do something. It seems bizzare that connecting in itself could set something off.

I guess the only way to find out would be to disconnect both airbags before trying and at this point I'm getting less curious !
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 02/03/2015 14:53

When you connect anything with a comms system to something else with a comms system, there is always the possibility, no matter how careful the designers have been, that an incorrect command finds its way into the system.

Warning after you've connected might be a bit late.
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 04/03/2015 11:47

YES - cleared the light finally.

I ended up using a cable known to have the FTDI chips in and the program Trw2Scan. (Just like Barney said wink )

For anyone interested here are a few things I found on the way. (Additional info and credit from this THREAD and this THREAD No claim to originality on my part , everything is a distillation of whats already out there. )

There appear to be four different airbag ECUs used on the Coupe. There was an early one from Becker. That is the one that has three wires to the diag socket and can be interrogated and reset by grounding one of the leads. The others 3 have two wires to the diag socket and were from TRW:

46306560 - A TRW2 type. Can be reset with TRW2SCAN.
46306172 and 46316266 - MY97 types. Can be reset with multiecuscan (or fiatecuscan).

Mine was a TRW2 type (it had 46306560 printed on its barcode.) So I can only comment on that from here on in.

Cables :- There are typically 3 types of KKL VAG OBD cables sold on ebay and as mentioned elsewhere you will also need the 3 pin Fiat adapter.

Cable 1 is a bog standard KKL/VAG/OBD . It will require CH340 serial drivers and WILL NOT work with Trw2scan. It will however give intermittent connections to the engine ecu using startrek and multiecuscan.

Cable 2 is the same as the above but has a 4 way switch incorporated into the body of the connector. I'm still waiting for delivery on this item.

Cable 3 is a KKL/VAG/OBD cable with the FTDI chipset. This is the cable that works "out the box" with Startrek / Multiecuscan and Trw2scan.

You can read all about the different programs on that link to the alfa forum given above but if you have the TRW2 airbag you will need to download the TRW2 program from HERE and the FTDI drivers from HERE

Note on Trw2scan : This is specifically for a TRW2 Airbag ECU which is found on some of the early cars and has TRW part number 60631206 printed on it's label (or 60625181 for the GTV 916 Phase 1). This model of Airbag ECU cannot be diagnosed or reset by any other DIY software available on the market.

If you have read earlier parts of this thread you can see I mentioned the dire warnings given by MultiEcuScan before attempting to connect to this type of ecu. Well the documentation for Trw2Scan gives the same dire warning but the program itself does not. So unless you read the documentation first you wouldn't see the warning. But then again its the only program that will work with the ecu so what choice do you have ???? Do as I did. DON'T sit in the car whilst connecting to the ecu.

Anyway once you have the right cable/software and driver then for this TRW2 type ecu simply run the program , (you must have the ignition on) it will connect and if it finds any errors it will report them and then ask if you want to reset the ecu. Just answer yes at which point the program will attempt to reset the warning light and exit.

Once the program exits the airbag warning light on the dashboard will still be lit. You have to switch the ignition off and back on for the light to clear. (Give it a few seconds as per usual)

The frustrating thing is that all the right info is on the forum but it took me so long and so much trial and error to sort it.

Thanks to the forum
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 04/03/2015 16:37

Nice one. thumb It's a great feeling when it finally works. smile
Posted By: dazzle

Re: Airbag reset with 2 wires for diagnostic? - 13/04/2015 15:03

Can you post a link to the correct cable that has the FTDI chipset please? Thanks
Posted By: Downhillryder

Re: Airbag reset with 2 wires for diagnostic? - 13/04/2015 22:47

Here's the link to both cables. (Replied to your pm)
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 14/04/2015 17:11

Downhillryder, thanks for all your investigation work on this subject. Well done for piecing it am together and supplying links. You'll save people (including me) substantial time and hard work.
This thread should definitely be a sticky.
Posted By: ScouseCoupe

Re: Airbag reset with 2 wires for diagnostic? - 10/07/2017 11:09

Originally Posted By Downhillryder


There appear to be four different airbag ECUs used on the Coupe. There was an early one from Becker. That is the one that has three wires to the diag socket and can be interrogated and reset by grounding one of the leads. The others 3 have two wires to the diag socket and were from TRW:

46306560 - A TRW2 type. Can be reset with TRW2SCAN.
46306172 and 46316266 - MY97 types. Can be reset with multiecuscan (or fiatecuscan).

Cable 3 is a KKL/VAG/OBD cable with the FTDI chipset. This is the cable that works "out the box" with Startrek / Multiecuscan and Trw2scan.


Thanks to the forum


Your great post sorted me out, though I would like to add over and above your comments that maybe there is 5 types ( 4 x TRW Type ) of ECU as mine is 46316722 from a 1999 reg Coupe connected with a KKL/VAG/OBD cable with the FTDI chipset, resets with multiecuscan under MY97 Types.
Posted By: Skiday

Re: Airbag reset with 2 wires for diagnostic? - 12/09/2018 18:32

The problem of an illuminated air bag light looks like it's a real nightmare. My coupé has been off the road for a year and I have swapped the steering wheel. Now I can't tax it because it has failed its MoT due to the air bag light, and the garage's computer can't talk to the air bag controller. So is there anything to do before going through everything on this and other related threads and buying a suitable cable? My car is a 2000 6sp+, does that narrow down the type of controller it has? And is there a cheat that will get me through the MoT so I can fix it at my leisure?
Posted By: Countrycruising

Re: Airbag reset with 2 wires for diagnostic? - 13/09/2018 07:06

Originally Posted By Skiday
The problem of an illuminated air bag light looks like it's a real nightmare. My coupé has been off the road for a year and I have swapped the steering wheel. Now I can't tax it because it has failed its MoT due to the air bag light, and the garage's computer can't talk to the air bag controller. So is there anything to do before going through everything on this and other related threads and buying a suitable cable? My car is a 2000 6sp+, does that narrow down the type of controller it has? And is there a cheat that will get me through the MoT so I can fix it at my leisure?


Check your emails Andrew.
Posted By: Skiday

Re: Airbag reset with 2 wires for diagnostic? - 13/09/2018 09:29

Thanks Joe. I covered the light with tape, but the tester would not accept that, so I'll try the bulb. According to the .gov web site it cannot be refused then. (but it seems much depends on the individual tester and how happy they are that day)
https://mattersoftesting.blog.gov.uk/common-mistakes-made-by-mot-testers/

I still want to make a proper fix though. I have ordered a VAG-COM KKL cable 409.1, but still need a fiat adapter. All Fiat/alfa adapters on ebay look as if they go from the big VAG-com block to a block about the same size, but the Coupé's connectors are all 22mm x 10mm. All the links from past posts are now dead, so what adapter do I need?

I did think that the ecu port with three wires (green/yellow , orange/white, and black) was the airbag port, but after much digging I know I was wrong and I have now found the correct port (with two wires and yellow sheathing). It is tucked behind the extra bit of triangular carpeted panel (pass side) that is by the heater above the carpet and has a vent hole in it. I think my garage made the same mistake so no wonder their reader couldn't talk to it.

It seem strange to me that a VW Audi Group cable is what is required. Is that what a Fiat dealer would have used when working on a new car?
Posted By: Countrycruising

Re: Airbag reset with 2 wires for diagnostic? - 13/09/2018 11:20

Along with the VAG cable you've ordered you'll also need this one, which is cheap as chips.
Posted By: Skiday

Re: Airbag reset with 2 wires for diagnostic? - 13/09/2018 12:58

Thanks Joe. That's the one. To save the problem of dead links for future readers of this, look in ebay for; "3 Pin to 16 Pin OBD2 Adapter Connector Diagnostic Cable Lead Wire for Fiat" Hope that helps others.
Posted By: Countrycruising

Re: Airbag reset with 2 wires for diagnostic? - 13/09/2018 13:34

thumb
Posted By: Skiday

Re: Airbag reset with 2 wires for diagnostic? - 14/09/2018 11:35

With great relief I can now say my air bag system is reset and the light is out, and the MoT is done. But it was not from the cables and software recommended on this forum. After showing the garage the correct ecu port they were able to talk to the ecu with their machine, which is a 'Snap-On Modus Ultra' but with using leads from their previous diagnostic machine, a Solus Probe (the engineer thinks that the Solus Probe would have worked too, but cannot confirm that). This is great because I tried to download the trw2scan and was told a FTD2XX.dll file was missing and I thought "Here we go", round and round trying to get the software downloaded, but the garage phoned today and told me the good news. Perhaps the cables I have bought will be useful for other diagnostic work later.

So the conclusion, your local garage can reset your air bag if they have the right machine and know the correct ecu port to enter.

Remember, the light not going out is an MoT failure, so get it fixed or, If you're happy for the air bag to be disabled, remove the bulb remove before putting the car in for MoT (You can't take it out after an initial fail as the tester knows the air bag is not funtioning, if there is no light in the first instance then he can't know there is warning system at all).

Love and pace to all.
Posted By: Countrycruising

Re: Airbag reset with 2 wires for diagnostic? - 15/09/2018 08:06

Well done Andrew, the cables recommended would rest it but like yourself I use a more modern Modus unit with older cables.
Posted By: godders

Re: Airbag reset with 2 wires for diagnostic? - 17/09/2018 00:10

Simply unplugging the connector from the Airbag ECU which is bolted to the transmission tunnel, behind the centre console, is far quicker than removing bulbs from the dash.
Posted By: Skiday

Re: Airbag reset with 2 wires for diagnostic? - 18/09/2018 11:29

I did quite a bit of rooting around looking for the correct port but I didn't see the ecu itself (or if I did I didn't realise it), so if anyone has a photo of it that might be handy.

So now I have cables to tap into the ecu (not just the airbag ecu but also other systems I presume as all the ecu ports seem to be the same) what other uses might they come in useful for?

btw, the air-con is now working after some 5 years or so without it. Yipee! It only needed a new condensing rad and dryer! I had to turn it off on the way home from getting it charged as it was too cold!
Posted By: DaveG

Re: Airbag reset with 2 wires for diagnostic? - 19/09/2018 10:46

The airbag ECU is bolted to the central raised part of the floor underneath the heater / centre console. If you have "plus" carpet extensions, the ECU, cabling and diagnostic socket will be hidden. Otherwise, all that stuff is easy to locate when looking from the passenger foot well.

Just look for the cables with a yellow sleeve. This pic shows the cables/sleeve, and shows the paper label still attached referring to "EURO-BAG" (and "CRASH SENSOR" on the ECU) as a clue. Here's a clearer pic of the ECU and diagnostic socket (lower left, it plugs into a dummy connector attached to a metal bracket).
Posted By: Skiday

Re: Airbag reset with 2 wires for diagnostic? - 21/09/2018 07:53

Thanks Dave thumb
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 23/10/2018 12:24

Downhillryder said
There appear to be four different airbag ECUs used on the Coupe. There was an early one from Becker. That is the one that has three wires to the diag socket and can be interrogated and reset by grounding one of the leads

well my car has a three wire socket so i would like to try to reset the light BUT - which of the three wires do I ground?
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 02/11/2018 14:44

well I am moving forward now - joined the club and got access to the manual and using the flashing codes of the air bag light I seethat I have three error codes :
4 blinks = wiring of module trigger circuits in contact with earth
6 blinks = resistance of passenger's module trigger device outside tolerance
7 blinks = supply voltage less than 9.5V.

Well I checked the voltage at the battery and get 13.5V. so that is a start. I suppose I now need to check the voltage at the fuse supplying the airbag control unit.
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 02/11/2018 15:59

I think one of the options is to reset the system. That would be a good place to start, since it will get rid of errors that have appeared in the past but are no longer present.
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 03/11/2018 12:05

a good idea barnacle - but how to do it?
p.s. if the fuse supplying the control unit is the one shown in my handbook ( just one of the general fuses in the box in the footwell) that is ok and giving around 13.5V.
Any advice on how to reset it would be most welcome please;
cheers
geoff
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 03/11/2018 20:29

According to the manual:

Originally Posted By Mr Fiat

After repairing the fault, repeat the test to make sure there are no other faults present. Bear in mind that the control unit communicates one fault at a time, until the system has been fully repaired. After completing the repairs, delete the memory by connecting the terminal no. 3 of the control unit for between 1 and 5 seconds. All the errors in memory must be deleted one at a time, repeating the procedure each time until the memory is deleted.


Which is not terribly clear, but I read as saying repeat the test multiple times until you get a single blink.
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 06/11/2018 12:42

no, it is not clear at all :
"delete the memory by connecting the terminal no. 3 of the control unit for between 1 and 5 seconds"
connecting it to earth ? I can only assume so.
I am getting three errors - one of which is :
7 blinks = supply voltage less than 9.5V.
I would like to clear this one up first because I think it might be causing the other two errors.
I guess this is the supply voltage at the fuse. Can anyone confirm it this is the regunar fuse in the fusebox or if there is a separate one for the airbag control unit?
Posted By: Anonymous

Re: Airbag reset with 2 wires for diagnostic? - 06/11/2018 12:56

The voltage error doesn't mean that the voltage is low right now, it means that at some point since errors were last cleared that the airbag ECU has seen a low voltage (maybe even just for a second) and as that may have caused a "brown out" fault or corruption of the ECU then it's flagged as an error.

Most likely your battery voltage got low at some point, but if it's OK now there's no point in checking fuses and voltages expecting to see a low reading.

Once the errors are cleared if you see the low voltage error again then you may want to replace your battery if the car is left standing without starting for a week or two. If the car is driven every day and you see the low voltage error appearing again then it would be time to start investigating the electrics for problems or a high current drain.
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 06/11/2018 17:53

I would agree with your assessment: connect it to earth (middle pin if I recollect correctly).

Each time you do it, it will flash out any stored errors. It will also clear those which are no longer active. So I'd take several attempts to read the errors and see if you get back to a no-error state. Or at least just one error to fix.
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 08/11/2018 07:43

so, thanks Barnacle. We are moving forward. I have now reduced the fault codes down to one.
4 flashes = wiring of module trigger circuits in contact with earth.
Has anyone figured out what this could be ,
cheers
geoff
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 08/11/2018 17:33

That sounds like a short circuit on the loom somewhere. The back of the radio is a common area for short circuits, and the wiring is probably going to be going somewhere in that area.

I *believe* that the 'module trigger circuits' are the drive signals that fire the airbags - either the passenger's above the glovebox, or the steering wheel.

Hmm, perhaps there's an issue with the clockspring in the steering wheel?
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 18/11/2018 10:40

thanks for this Barnacle. sorry for the late reply. (Been to Uk and was very pleased to see the lovely display of Coupes at the NEC. Thanks to all involved. I know from my time with the Panhard club that it is very time consuming.)
Ref your first sentence, do you think I only need to restrict my search to the yellow sleeved part of the loom - or the whole loom in general?
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 18/11/2018 21:02

It's been a few years since I've looked at the loom in that area, but *as far as I remember* all the airbag loom has yellow sleeves.
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 20/12/2018 16:43

so nothing obvious visibly so far in the centre console but we still have
"4 flashes = wiring of module trigger circuits in contact with earth" so I need to now start dismantling either the drivers or the passengers airbag to invesigate further.
I would appreciate some advice on which side is the most likely culprit?
cheers
geoff
Posted By: barnacle

Re: Airbag reset with 2 wires for diagnostic? - 23/12/2018 06:13

The moving parts are in the steering wheel, where the clockspring carries the signal. Other than that, you're looking at vibration chafing the insulation in the loom. I think it's unlikely to be anything in the airbag units themselves.

One thing to remember: the airbag is an explosive device... when dealing with it, first remove the battery and wait half an hour for any residual capacitors to drain before you dive into the wiring.

When you put it back together, *particularly* as you have a fault on the system, turn the ignition on first and only then reconnect the battery. That way, if it does go bang you're on the outside of the car...
Posted By: Yann

Re: Airbag reset with 2 wires for diagnostic? - 09/01/2019 18:57

Error n°4 is probably the clockspring.

I had a few errors previously and n°4 was one of them :
https://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1587739#Post1587739

Today I fitted another ECU. Again, as I fried the previous one at the same time I fried the main ECU... Light off, but only for a few seconds. I've been able to clear 2 of them, the one about the voltage, and the one about the bulb wiring (will maybe reappear). The unknown error n°9 is no longer there, and error n°4 neither. I repplaced the clockspring a few months ago (but the ECU was dead) so it must be the reason.

Now I still have one error, and it wasn't present (I think, I don't remember if it was present when I last checked the dead ECU):
6 - Resistance of passenger's module trigger device outside tolerance

But I don't have a passenger airbag. There is a resistor (I think) behind the glovebox, it gives me 3 Ohms when I measure it.

I don't understand this error. I don't understand how the ECU can know it comes from the passenger side as all the cables going to the driver and (supposed) passenger airbag are connected together on the ECU plug.

Maybe it says it comes from the passenger side by default (because it can be disabled manually if present) and in reality it comes from the driver side ?
Posted By: Yann

Re: Airbag reset with 2 wires for diagnostic? - 10/01/2019 12:43

I tried disconnecting the driver airbag, and it triggers the error related to it, so it's not the culprit. Maybe the resistor in the passenger side is not correct anymore.

Anyone knows what the resistance value should be ?
Posted By: Yann

Re: Airbag reset with 2 wires for diagnostic? - 19/01/2019 18:05

After searching the forum, I found that 2.2 Ohm resistance should do the job (and now I see in the manual that the airbags are 2.15 Ohms +/- 0.35). THe one installed is 2.7 Ohms.

So I tried with a 2.2 one, tried to clear the fault, it didn't work, but after starting the engine, the light turned off. I decided to replace the old resistance by the new one on the original plug, and tried again. Light came back. And starting the engine / trying with another resistance without soledering it doesn't change anything.

What's wrong ? Can the light go off if I drive the car a bit (the manual states there is an initial test when switching the ignition ON then a continuous test while driving) ?
Posted By: Yann

Re: Airbag reset with 2 wires for diagnostic? - 29/01/2019 16:20

Ok, easy fix. Fitted another airbag ECU today after reading this http://forum.alfa145.com/index.php?showtopic=9670, no more passenger airbag error. I will ask for a refund for the defective unit.
Well, light came back.
Posted By: mli

Re: Airbag reset with 2 wires for diagnostic? - 31/01/2019 20:52

renault and Yann

I didnt read all post - but at least a few comments:

1) I used trw2scan with a standard VAGCOM/KL OBD cable and the 3pin Fiat adapter - connected to the loose cable-connector coming out from airbag sensor unit behind the radio.
(I did have to fiddle with port/conn a bit as I recall)
With this I could reset all but one error - which was a real error...

2) I had water from heatingsystem dripping into cables/connector on ABS-unit :-/
= giving internal mem-error on the airbag unit (reported by trw2scan

3) I the end I made a short from ABS to airbag lamp behind dash - neatlyturns on/off together (= looks correct).

see more here:
https://www.fiatcoupeclub.org/forum/ubbt...248#Post1621248

contains info on different airbag units as well... (from some other clever bloke)
You can't always exchange airbag units btw diff coupe models.

Cheers,
M
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 02/02/2019 13:22

what a great idea mli - shorting the lamp to the ABS one !!
I think I will do this as a temporarry measure to get through the controle technique.
cheers
geoff
Posted By: Yann

Re: Airbag reset with 2 wires for diagnostic? - 04/02/2019 17:01

Originally Posted By mli
renault and Yann

I didnt read all post - but at least a few comments:

1) I used trw2scan with a standard VAGCOM/KL OBD cable and the 3pin Fiat adapter - connected to the loose cable-connector coming out from airbag sensor unit behind the radio.
(I did have to fiddle with port/conn a bit as I recall)
With this I could reset all but one error - which was a real error...

2) I had water from heatingsystem dripping into cables/connector on ABS-unit :-/
= giving internal mem-error on the airbag unit (reported by trw2scan

3) I the end I made a short from ABS to airbag lamp behind dash - neatlyturns on/off together (= looks correct).

see more here:
https://www.fiatcoupeclub.org/forum/ubbt...248#Post1621248

contains info on different airbag units as well... (from some other clever bloke)
You can't always exchange airbag units btw diff coupe models.

Cheers,
M



The ABS light trick is a known one.
I prefer to fix the problem first. If I can't, I will probably just disconnect the ECU, it may pass the MOT as it doesn't seem to be in the list of MOT defaults.
Originally Posted By renault
what a great idea mli - shorting the lamp to the ABS one !!
I think I will do this as a temporarry measure to get through the controle technique.
cheers
geoff

Même souci, ça va surement finir de la même façon... Je me demande si le fait de débrancher l'ECU (donc pas de lumière) ne passerait pas, ce n'est pas dans la liste des points soumis à contre visite...
Posted By: renault

Re: Airbag reset with 2 wires for diagnostic? - 04/02/2019 17:22

je ne suis pas sur en angletere, mais on france il faut allumer la lampe pour passer le controle technique.
It is necessarry for the light to show and then to extinguish in order to pass the controle technique here in france.
Posted By: Yann

Re: Airbag reset with 2 wires for diagnostic? - 12/02/2019 20:56

Looks like I fixed my error about the passenger resistance. As the new resistance I fitted wasn’t working better than the old one, despite its lower value and another ECU was showing the same error, it must be the wiring. I already checked the continuity but it was fine. I was going to try another wiring, but someone advices me to put the resistance directly on the ECU, easier, faster and no problem because of the wires. So I opened the red plug and fitted the resistance between cables 2 and 5 and reassembled the plug as it should be. I removed the resistance from its original place, behind the glovebox.

Ignition ON, and light went off as it should, no need to reset the ECU.
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