Another (slightly different) Fiat airbag warning thread with fix

[Googlebot]

A few times the last few months, the dreaded airbag warning light has come on. Base is a 2013 Fiat Ducato.

I have owned it for 5 years and once got a warning as I got up off the seat a few years back. Put that down to a dodgy connection as checked them all and it never came back.

The last few months though, it has come on about 4 times then cleared. Code reader says low voltage fault or connection error.

Happened to have left the Victron app open last time it came on and noticed how low the starter battery was when the B2B cut in. I only fitted the second B2B this year and it coincides with the warnings.

I am running 2 B2B’s, a Victron XS and another 30amp one, both off a D+.

Checking the graphs, when the lithium is low, the starter battery takes an age to come up to a decent voltage. This may be because my alternator can’t cope (unlikely as it’s a 150amp) or just the fact that it’s getting on a bit.

I thought about it and every time I have had the warning has been when the lithium is low and I start the van and don’t immediately pull away, thus bringing the revs and alternator voltage up.

On idle with low lithium, I have seen the voltage of the starter battery drop to 12.5, not ideal.

I have now set the XS to cut out if the battery voltage drops below 13.1v and so far, no repeat of the issue.

I was preparing myself for a massive bill for a new module, hopefully this is the cause and fix. You can see in the picture below how the voltage gets pulled down as the leisure batteries charge. I probably need a better data logger for the starter battery to be sure.

 

[Googlebot]

I spoke too soon, light came on again yesterday. Went off and on a few times then stayed on. Now have the internal control unit error coming up on the fault codes.

Looks like it’s toast!

On the plus side, I can code it myself with the software I got for the DPF error.

That’s another £250 gone.

 

[Silver-Fox]

These Fiats are at best challenging to say the least.

The Daughters van has thrown up fuel filter twice even though we’ve changed it.

And another fault I’ve forgotten.

Another odd one is the cab battery has drained down enough not to start the van.
It’s the original battery so I changed it yesterday.

French electrics

 

[Lenny HB]

French electrics

They are Italian.

 

[Silver-Fox]

They are Italian.

Even worse

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[Googlebot]

To be fair, the Mercs at work have just as many problems. At least the Italians are consistent in their cock ups.

 

[Bessy765]

We are going to Adams Morey on the way home from Portugal (Portsmouth ferry) to have a new ecu and battery fitted. Had van from new (2019) still the original engine battery but with 700 watts of solar and 2 x 100 Lithium, starter battery has always been maintained and not run low. Good old Fiat and others makes.

 

[Sleeveless]

What's the fault code for the internal ECU error ? B100-49 can usually be easily rectified . Voltage induced errors however usually affect the EEPROM chip's crash data template and need specialist rectification. Regarding the battery voltage with a 150 amp alternator, having also observed the marginal voltage issue, I've fitted 2 timed relays to delay the activation of both the fridge 12v element & DC-DC charger for approx 5 mins after start. From cold start, the glow plugs are still operating and drawing a considerable load during the warm up phase, (later engines employ PWM to control the plugs more efficiently) . With a Renogy DC-DC it's also possible to limit the charge current to leisure batteries by 50% with a switch , especially useful when charging lithium batteries after discharge.

 

[Googlebot]

What's the fault code for the internal ECU error ? B100-49 can usually be easily rectified . Voltage induced errors however usually affect the EEPROM chip's crash data template and need specialist rectification. Regarding the battery voltage with a 150 amp alternator, I've fitted 2 timed relays to delay the activation of both the fridge 12v element & DC-DC charger for approx 5 mins after start. From cold start, the glow plugs are still operating and drawing a considerable load during the warm up phase, (later engines employ PWM to control the plugs more efficiently) . With a Renogy DC-DC it's also possible to limit the charge current to leisure batteries by 50% with a switch , especially useful when charging lithium batteries after discharge.

It is indeed, that code.

I haven’t heard great things about them being repaired and I have the kit to sort a new one at home.

I have a feeling the low voltage error was a red herring, it should be able to withstand less than 12v for a short time in normal use and the amount of failures would suggest the ECU is just not fit for purpose.

 

[Sleeveless]

It is indeed, that code.

I haven’t heard great things about them being repaired and I have the kit to sort a new one at home.

I have a feeling the low voltage error was a red herring, it should be able to withstand less than 12v for a short time in normal use and the amount of failures would suggest the ECU is just not fit for

It is indeed, that code.

I haven’t heard great things about them being repaired and I have the kit to sort a new one at home.

I have a feeling the low voltage error was a red herring, it should be able to withstand less than 12v for a short time in normal use and the amount of failures would suggest the ECU is just not fit for purpose.

It may just need a simple repair , this fault is usually caused by a poor ground contact between the airbag ECU's circuit board and the unit's casing ( which is grounded by being bolted to the chassis) . Fiat issued a service doc involving adding an additional ground strap but the problem is inside the unit. By removing the ECU and taking the back cover off. the ground contact points on the PCB can be carefully cleaned , restoring the contact and eliminating the resistance which generates the fault code , see pic, contact areas circled pink . The fault can then be erased . This ECU is not sealed against the atmosphere so damp can get in . Don't use anything abrasive when cleaning contacts though as they have a very thin silver coating.

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[Googlebot]

It may just need a simple repair , this fault is usually caused by a poor ground contact between the airbag ECU's circuit board and the unit's casing ( which is grounded by being bolted to the chassis) . Fiat issued a service doc involving adding an additional ground strap but the problem is inside the unit. By removing the ECU and taking the back cover off. the ground contact points on the PCB can be carefully cleaned , restoring the contact and eliminating the resistance which generates the fault code , see pic, contact areas circled pink . The fault can then be erased . This ECU is not sealed against the atmosphere so damp can get in . Don't use anything abrasive when cleaning contacts though as they have a very thin silver coating.



View attachment 994092

Thanks for the tip!

Will try that and see how it goes, will update the thread then.

It was indeed, damp as anything in the van with all the mist and fog around.

 

[growly_bear]

Thanks for the tip!

Will try that and see how it goes, will update the thread then.

It was indeed, damp as anything in the van with all the mist and fog around.

That's very interesting. Away today for the first time in a month. Very cold and misty in the Peak District. The amount of condensation on the steel cutlery, pot mugs and even the leatherette backgammon set was crazy!

So all things considered, I'll bet the airbag ecu is just as wet.

If I open the ecu up, I'll be tempted to follow the pcb earth tracks and fit an additional earth to the wiring and not just the case.