Fiat ducato air bag warning light is on…..AGAIN.

Camper634

Camper634

Joined
Dec 18, 2011
Posts
777
Likes collected
535
Location
Hull
Funster No
19,200
MH
Autotrail 634
Exp
Since 2006
For the 3rd time in less than 12 months the air bag warning light is back on the dash.The last time was 6 weeks ago when it cost me £88 with crashdata to have the module reprogrammed.I did ask the question then why has it gone again.One of the replies it could be high voltage when starting the engine.So every time since the last replacement i have turned the ignition to on and waited until the various lights went off before cranking the engine.This morning i only tuned the ignition on to check mu LPG levels and almost immediately the air bag light came on.
I am at a loss what to do next.I cant keep paying £88 God knows how many times.Has anyone please got/had this problem and found out a reliable fix?Any help greatly appreciated.
 
Sort by date Sort by votes
Bramidan said:
Right I am a newbie and know nothing so please be gentle.
If this warning light is on does it fail the MOT?
Does it mean the airbag won’t work?Can you drive the vehicle with the light on?
Coukd you just disconnect it?
Click to expand...
It’s a mot fail.
Airbag is out of action.
Yes you can drive I did for several weeks with no other effects.
 
Upvote 0
TheBig1 said:
Now bear with me as I explain a little background info. If we want to run something sensitive to the supply voltage in the van, we fit a device between supply and device. This is called a buck/boost voltage stabiliser circuit. I use them for running the 12v router and protecting from under or over voltage.

This device takes the incoming voltage and the circuit either amplifies the voltage whilst lowering the current of the output or detects over voltage and cuts it off at the precisely set required output. If you use a good one, it will detect and block voltage spikes and cut these off too. All for a minimal power drain on the supplying system.

Now reduce the airbag circuit and it's ecu to a diagram and you will see that some, but not all of the components rely on a voltage change to detect a fault in the circuit or worse a possible impact, so compares the reference voltage being supplied with the "fault/alarm". If the incoming positive feed to the ECU is corroded or significantly under or over voltage the memory on the ecu can get corrupted. Hence reflashing the code fixes most faulty ecu's

Back to the buck/boost circuit. Why can't we fit a buck/boost in the supply wiring to the ecu? This would be pre-set to the exact voltage the ecu needs and assuming care was taken to avoid the plug/socket getting corroded would prevent this issue happening again. Obviously it will not stop the ECU from developing a hardware fault, but will go a long way to saving low or high voltage scrambling the memory it holds.

Another possible issue is dry solder joints, letting go due to constant vibration in a vehicle, especially being mounted on the metalwork close to the engine and drivetrain. I am sure that crashdata but these faulty units on a test rig and install a standard copy of good data. If they won't take data they get inspected for damage, but doubt they test all the solder joints as it is time consuming. A unit that repeatedly goes into fault at random likely has this issue
Click to expand...
I use these to supply my router and also my Truma Combi4. The boiler used to go into jet engine mode followed by the red light cut-out, under certain conditions, usually if the water heater had been on and then the space heating was switched on. I am convinced this was caused by a voltage spike due to the battery charger engaging because a large amperage was drawn by the Combi sending the charger into boost mode 14.4v. I replicated the fault many times. I then tried the system with the onboard charger off. The fault did not occur. I used a 6amp 12v power supply by simply using the Combi feed as the input and connected the output to the Combi. Result, the fault has not occurred for a year or more.
So yes the addition of a regulated power supply to feed the airbag module should negate any high or low voltage problems.

Geoff
 
Upvote 0
Think yourself lucky that motorhomes are still relatively a commercial vehicle. An airbag fault on some cars will put the vehicle in limp home mode and display a "contact dealership immediately" message on the screen for safety. Most on here have driven loads of vehicles before air bags were a thing on vehicles, even before seatbelts as well

Subscribers  do not see these advertisements

 
Upvote 0
This site contains affiliate links for which MHF may be compensated.
Upvote 0
I think the air bag ecu is damaged (electronically) and is then tested with multiscan. I don’t think the repair is as simple as just clearing the fault code in the unit. Otherwise the main dealers wouldn’t be fitting new units.
 
Upvote 0
Having seen Gellyneck photo of Multiecuscan print out
i checked the Multiecuscan website and found this reply on the forum.
No garentee that this would work, but if you have MES and the problem.


04 Feb 2022, 10:22

Thanks for the reply.
I did the Proxi Aligment and the airbag light went out - even with nothing (not even a resistor) connected to the pretensioner lead.

I wonder if the proxi alignment sort of says to the vehicle to calibrate itself to as it is at that moment in time and if anything changes in the future then it lets you know with a warning light?

Anyway, all is good (at the moment!).

Another post concerning connection to airbag ecu (whether this was with a KKL or obdlink cable i'm unsure)

I did, in fact contact MES support, and they were great! Solution (or workaround!) is to "Shift+F10" to connect to the airbag module, which forces the unit to switch into KKL compatibility mode
:)
It worked
:)


ps this is undoccumented
 
Last edited:
Upvote 0
Someone asked if this also affects Citroen/Peugeot. The answer is yes since these elements are common across all three ranges. I am presently waiting the return of my airbag controller from CrashData for my Citroen-based PVC. This is the second occurrence in 12 months and I have now removed the link between my solar controller and the van battery/alternator to see if that prevents these alleged “high voltages”.

My understanding is the “resetting” done by CrashData may involve re-flashing an eeprom within the controller. I doubt that this is done with MultiECUscan, although the latter is clearly used to provide before and after testing of the controller as seen in the supplied printouts.
 
Upvote 0
I have a '68 Elddis on a Peugeot Boxer, airbag warning light came on about 3 weeks ago Code B0100-8F.

Not sure 100% on timing but over the same weekend I lost output from the dash 12V cigarette lighter socket which I use for a supplementary garmin truck satnav.

Possibly a spike has taken out it's supply fuse (not located it yet, think it's in the under the bonnet fuse panel somewhere?) and maybe put a high supply on the airbag ecu?

Regarding TheBig1 's thoughts on providing a regulated 12V supply for the airbag ecu.
I have a spare Cello TV regulator unit like this one. Would it be possible to re-purpose it by cutting off it's cigarette lighter plug and splicing it in to regulate the airbag ecu supply?
 
This site contains affiliate links for which MHF may be compensated.
Upvote 0
🤔 I wonder if these high voltage fault codes are triggered by transient high voltage spikes, maybe when the starter motor stops. Some of the reports show 14 odd volts but that isn't high.. something's triggered it. 🤔

If mine goes I'd fit a 16v Zener diode on the power supply.

Subscribers  do not see these advertisements

 
Upvote 0
Richard n Ann said:
🤔 I wonder if these high voltage fault codes are triggered by transient high voltage spikes, maybe when the starter motor stops. Some of the reports show 14 odd volts but that isn't high.. something's triggered it. 🤔

If mine goes I'd fit a 16v Zener diode on the power supply.
Click to expand...
Hi
Why not fit one before it goes? It's a bit later after :unsure:

Geoff
 
Upvote 0
Camper634 said:
For the 3rd time in less than 12 months the air bag warning light is back on the dash.The last time was 6 weeks ago when it cost me £88 with crashdata to have the module reprogrammed.I did ask the question then why has it gone again.One of the replies it could be high voltage when starting the engine.So every time since the last replacement i have turned the ignition to on and waited until the various lights went off before cranking the engine.This morning i only tuned the ignition on to check mu LPG levels and almost immediately the air bag light came on.
I am at a loss what to do next.I cant keep paying £88 God knows how many times.Has anyone please got/had this problem and found out a reliable fix?Any help greatly appreciated.
Click to expand...
It would be interesting to see what Camper634's fault was this time round, if it is high volts and he has a solar panel charging the vehicle battery then this maybe the issue as there is nowhere else the high voltage can come from as the engine wasn't running. Someone else mentioned ambulances, they too have the same setup as Motorhomes regarding solar panels.
 
Upvote 0
BobJayne said:
Why 16V though when quite a few people have had reports back saying High Voltage of 14.6V detected?
Click to expand...
I'm no expert but 14.6 isn't particularly high, maybe a transient Spike of a few hundred volts triggers the overvoltage alarm and it's that brief the normal voltage is recorded as the fault.
Oh also I've got 16v 1.3w ones in stock 😜
Could be that the ecu's own suppression zener goes faulty, therefore they can be fixed but after a few starts you're back to the fault code again.

All just guesses, it probably none of the above 🤣
 
Upvote 1
Hi,
The voltage reported is just the freeze frame data at the time of the fault occurring. The voltage may not have been the problem.
Crash data sent me mine back saying 14.4v was too high - when I asked what was acceptable they would not reply to me.
My repaired unit blew again within an hour on the first trip out so I replaced it with a new unit from Crash data. Not cheap but so far no further issues.
I also noted that the airbag ECU over reads the input voltage by around 0.5v whereas the engine ECU reads correct.


Andy

Subscribers  do not see these advertisements

 
Upvote 0
The thing is the alternator voltage would be higher than that anyway and maybe a ehu charger too.
Also, what wattage zenor diode, 1.3W available on the-bay. Would the zenor diode not just blow anyway with a spike?
Anyone got a dud ecu to open it to see what's inside component wise?
 
Upvote 0
BobJayne said:
The thing is the alternator voltage would be higher than that anyway and maybe a ehu charger too.
Also, what wattage zenor diode, 1.3W available on the-bay. Would the zenor diode not just blow anyway with a spike?
Anyone got a dud ecu to open it to see what's inside component wise?
Click to expand...
I fit a 10 ohm resistor in series, I suppose the current will be that brief it won't overload the Zener.
 
Upvote 0
Upvote 0
Interesting that the ECU detects the input voltage, previously my Sargeant EC500 PSU was being tripped by my solar panel in bright sunlight only, the solar panel controller was outputting 14.8V and the EC500 is set to trip at 15V. With the help of Sargeant support the fault was diagnosed as the EC500 reading 0.3V high. The unit was replaced and been OK for the last three years. I am also waiting on the return of a faulty ECU and seeing high voltages quoted above as 14.4V, 14.6V, certainly a lot lower in what my solar panel controller is capable of outputting (14.8V with bright sunlight), food for thought.
 
Upvote 0
I copied the one from Richard n Ann, no idea why it showed as you.
The images are from a previous thread

BobJayne said:
The thing is the alternator voltage would be higher than that anyway and maybe a ehu charger too.
Also, what wattage zenor diode, 1.3W available on the-bay. Would the zenor diode not just blow anyway with a spike?
Anyone got a dud ecu to open it to see what's inside component wise?
Click to expand...

FIDGET said:
Hi Larby , where did you find my original post , I can't remember ever posting it. thanks
Click to expand...
 
Upvote 0
Camper634 said:
We could start by making sure never to buy another Fiat but that would rule out 80% of motorhomes.Dealers aren't interested once you hand over your cash and drive away.If this was in the car industry there would be hell on.
Click to expand...
What you could do is get legal help as a group, if a lot of people sign up for it then fiat will jump into action!
 
Upvote 0
cgwcmlw said:
It would be interesting to see what Camper634's fault was this time round, if it is high volts and he has a solar panel charging the vehicle battery then this maybe the issue as there is nowhere else the high voltage can come from as the engine wasn't running. Someone else mentioned ambulances, they too have the same setup as Motorhomes regarding solar panels.
Click to expand...
Solar panel regulator max voltage output is near enough the same as the vehicle alternator. "High voltage" is likely to be triggered by a spike a lot higher than those mentioned so far. By the time the fault code is triggered only system voltage will be available to read. I think I'd consider finding the point at which the SRS ECU connects to earth and checking whether the connection is sound and not shared with a high current device.

Subscribers  do not see these advertisements

 
Upvote 0
I don't see how they can claim 14.6v is high voltage when the alternator kicks out 14.5, the 14.6v they are quoting is from their Multiscan reading.

They still haven't received my unit I sent it special delivery on Thursday, and they said they would want me to pay again to reset it, it failed less than two weeks after getting it back, not impressed.
I've asked them if they will credit the original payment against a new unit they have sort off agreed.
 
Upvote 1

Join us or log in to post a reply.

To join in you must be a member of MotorhomeFun

Join MotorhomeFun

Join us, it quick and easy!

Join us

Log in

Already a member? Log in here.

Latest journal entries

Back
Top