Technical Diesel Ducato Electrics gone haywire

[Larryinkernow]

Hey all, my 2018 Ducato is throwing every warning possible on the dash, even including things like High temp (when cold), immobiliser light is now on permanently so it won't start.

We had the windscreen replaced 3 months ago and just learned about the scuttle problem after 3 months of savage British winter. I heavily suspect it's water ingress, but after drying out and checking ECU/BCM/ looms etc it all looks ok.

I scanned with Multiecuscan and it gave me a shopping list of errors (see attached). Has anyone had anything similar?

Even if i remove the key, the lights will turn on and flicker and the dash/ radio come on. Only way to stop the van draining itself is to disconnect battery.

RAC said there's no hope and gotta take to Fiat Dealer, but they say 4 weeks before they can even look at it.

 

[Communicator]

With my smattering of knowledge in that area, I cannot claim to be an expert on x250/x290 models, however some possibilities do come to mind.

The instrument panel, radio, BCM, are all nodes on the canbus together with the engine management and other processors.
Lights are controlled by the BCM, and faulty BCMs keep being mentioned in these columns. Key code system is also embodied in the BCM

1. I doubt that this is the cause, but a faulty engine block earth strap can cause spurious alarms. Is earth strap sound? It can have internal corrosion.

2. The "rusty junction syndrome" is a hidden problem below the LH headlamp where a wiring form abrades against a tubular frame member, rust sets in and wears through the wiring insulation. As this is close to the ECU, it is conceivable that the canbus wires could be damaged. Eliminate by removing headlamp, and lifting the wiring loom to inspect. Photo courtesy of @Reg 65.

3. Consider having the BCM tested by a specialist company.

 

[Larryinkernow]

With my smattering of knowledge in that area, I cannot claim to be an expert on x250/x290 models, however some possibilities do come to mind.

The instrument panel, radio, BCM, are all nodes on the canbus together with the engine management and other processors.
Lights are controlled by the BCM, and faulty BCMs keep being mentioned in these columns. Key code system is also embodied in the BCM

1. I doubt that this is the cause, but a faulty engine block earth strap can cause spurious alarms. Is earth strap sound? It can have internal corrosion.

2. The "rusty junction syndrome" is a hidden problem below the LH headlamp where a wiring form abrades against a tubular frame member, rust sets in and wears through the wiring insulation. As this is close to the ECU, it is conceivable that the canbus wires could be damaged. Eliminate by removing headlamp, and lifting the wiring loom to inspect. Photo courtesy of @Reg 65.

3. Consider having the BCM tested by a specialist company.

Thanks, i'll check the rusty junction and report back. For BCMS, do you need to take and send off, or get someone to visit?

 

[deejays]

To rule out any earthing or supply issues to each Electronic Control Unit use MES to monitor the voltage supply rail in the Parameters Tab for each ECU. If that checks OK, then likely issue is CANBUS continuity either due to water ingress in connectors or chaffing etc. A PicoScope would be the best tool for that. How good is the starter battery itself?

 

[Larryinkernow]

To rule out any earthing or supply issues to each Electronic Control Unit use MES to monitor the voltage supply rail in the Parameters Tab for each ECU. If that checks OK, then likely issue is CANBUS continuity either due to water ingress in connectors or chaffing etc. A PicoScope would be the best tool for that. How good is the starter battery itself?

That's a good idea. Starter battery is solid, I don't think there's any issues there.

Just checked all the rusty junction bits and nothing off there. Gonna check the c010 earth's tomorrow.

Hopefully can find an auto electrician to take a look at it. Anyone know any ducato specialists in mid Cornwall?

 

[Communicator]

Thanks, i'll check the rusty junction and report back. For BCMS, do you need to take and send off, or get someone to visit?

Remove and send away. I have a memory of a recent thread relating to failures of BCMs in early 2008? vehicles. As I recall two members were recommending the same repairer, but I think that the work was for cloning recovered BCM's. Perhaps you can search for the thread?

 

[Larryinkernow]

Ok, so coming back with some more info and a suspected culprit. Autosparky came out and had a look, couldn't find anything that was causing a problem, and able to "talk to" ECU, BCM and other modules. The one consistent error that kept coming up was the Airbag ECU. When trying to talk to Airbag the Fuel gauge dropped on the dash and the temperature display read _ _. On investigation, we found corrosion in the right hand connection/ harness. One pin on the Airbag ECU is corroded off.

Apparently this could well be the cause as the Airbag "wakes up" the system along with the door opening - hence the crazy electrics when the van battery is connected? Apparently the CAN BUS is a lazy bit of kit that can draw from otherplaces, or get interupted by faults when it's trying to communicate. I'm not sure if this explains the sidelights turning on intermittently, but we'll find out.

I'm going to order a new Airbag ECU, and i believe i can then do a proxy align with MES? More research to do and reading up the Airbag threads on it, but if anyone has any thoughts please do let me know. Much appreciated!

 

[Larryinkernow]

Also to add, Auto sparky didn't think it was the BCM because it wasn't clicking in before the issues start. I assume he's referring to relays or something.

 

[Larryinkernow]

Ok, so airbag ECU replaced with brand new part, all connections squeaky clean but still no joy.

Main symptoms:
Van wakes up with key out when the battery is connected: radio comes on, sidelights/headlights come on intermittently, and there is a high pitched buzzing when they do

Dash warnings go crazy. Sometimes it behaves normally, I can drive it, then after parking it may start flickering again.

Engine runs perfectly, and drives great without all the warning lights, if I can start it when the intermittent immobiliser lamp isn't on.

What’s been done:
Auto electrician can out and couldn't find anything amiss except airbag ecu. This was corroded with a broken pin, now replaced.

PROXI alignment completed.

Earth strap replaced

Under-bonnet fusebox checked, ECU connectors reseated, steering column/rack plugs checked.
Diagnostics:

CAN resistance at OBD pins 6–14 = ~61Ω (so CAN pair/terminations seem OK).

MultiECUScan: I can usually connect to Engine ECU, and just got the gendan adapters but the Body Computer (BCM) is sometimes “Unable to connect” (it did connect earlier in the process). Sometimes it shows Vin as?????

Errors:
There are loads, but themes repeat across modules:
B-CAN/C-CAN missing messages / “general electrical failure”
Instrument panel signal/message invalid
Brake pedal switch signal invalid (in ABS)
Steering angle calibration/missing message
Previously had immobiliser/key-related errors too (immobiliser light was stuck on earlier, but it did clear and the van started).

Question: Given airbag ECU replaced + PROXI done, CAN resistance looks normal, but the van still wakes with key out, radio comes on and headlights lights turn on intermittently, where would you focus next?

Does this sound more like ignition backfeed, BCM/under-dash fusebox power/earth issue, high resistance main feed/ground, or something else? I'm learning as I go so any thoughts appreciated!

 

[lycopersicum]

Not sure about the 2018, but on my 2013 model there are two CAN buses, I think only the B bus is available at the OBD connector and the C bus is not. The BCM is the junction between the two buses.

If the system architecture is substantially the same as mine, then some of the nodes you're getting errors about are on CAN B and some are on CAN C. As both buses seem to have problems, that would in my opinion exclude the individual buses and point towards:
- a fault in the BCM itself
- a fault in the BCM junction box and its connectors
- unstable ground or power, to be diagnosed with an oscilloscope (a multimeter won't cut it)

 

[lycopersicum]

See also: https://www.fiatforum.com/threads/haunted-ducato.506087/

Where the issue was the BCM.

 

[Larryinkernow]

See also: https://www.fiatforum.com/threads/haunted-ducato.506087/

Where the issue was the BCM.

Ah yes, I did read this as I'm sure my van is also haunted! Thanks for your info on the CANBus junction, that would make sense, all connections are clean and I've checked most earth's I can find, a faulty BCM is my top suspicion.

 

[Communicator]

See also: https://www.fiatforum.com/threads/haunted-ducato.506087/

Where the issue was the BCM.

And there have been others!

 

[Larryinkernow]

So i replaced the BCM with a cloned version from Dashmaster, sadly no fix there. This is some feedback from the latest diagnostics:

I know what circuit we are looking for I can start closing in on it.I have this blue and yellow wire that has around 145ohms to the effected ignition circuit. I can simulate the fault by injecting 1.8v into the ignition circuit, but also by doing the same to this blue/yellow wire I see around 1.2v which is inline with the fault Impedance of 145ohms, that resistance increases as voltage increases which strongly points to that being the fault. When I put my meter on I get a reading that gradually decreases, it's a red flag, it shouldn't be transient. The fault only occurs when both are connected to the BCM dispite the fault current being on the wires when disconnected so although the fault exists pushing current into the circuit, the only symptom would be the airbag light flickering, there would be no sidelight, stereo etc.. Without the BCM involved.This proves a few things.The fault exists when disconnected from BCM but it doesn't cause a wakeup. It's also not a full wakeup. When the fault drops below threshold it goes back to sleep in seconds, where as turning hazards on causes a wakeup and sleep cycle lasting over a minute.We know there's voltage creeping into the dash ign output from BCMThere's 2 circuits with low transient Impedance between them when seperate from BCM.The fault Impedance behaves like a wiring fault. Resistance drops with a very low voltage across it, but goes up when loaded and then tails back off when removed.The fault is always detectable at around 0.7v. It creeps up to around 1.1-1.2v where we start to see the airbag light flicker.Over 1.2v the interior light starts to come on and off with the stereo. It also triggers the sidelight relay. That current draw seems to cascade into more regular fault current as I'm guessing it's drawing across its own fault circuit causing a feedback loop between the fault showing symptoms, and those symptoms causing the fault to become more unstable. Then all of a sudden the cycle breaks and it drops back to 0.7v. Even up until the point I snipped that blue wire I still couldn't get my head around how it wasn't the BCM, but it does make sense now.


£1000 down and we are still no closer to finding the cause of the random wakeups

 

[348azeus]

I had a similar problem with my dash panel going nuts. Often the engine compartment fuse box can suffer from water ingress. I changed mine for good measure but I had actually suffered water ingress into the engine ecu. If it was damp or rainy the van would cut out and the dash would start flashing like a pub disco. A virginised ECU cured it together with a diversion of the scuttle drains.

 

[Larryinkernow]

So after a long long time of searching, we found the cause of our electrical gremlins. It was a spare plug with a cap full of water in the footwell. Power and return feed had created their own connection through electrolysis, which gave variable voltage, but just enough to make the bcm think it was getting a wake-up signal. Cleaned up and all good now.

(I know the vans filthy, was a ex work van)

 

[jackwhoo]

So after a long long time of searching, we found the cause of our electrical gremlins. It was a spare plug with a cap full of water in the footwell. Power and return feed had created their own connection through electrolysis, which gave variable voltage, but just enough to make the bcm think it was getting a wake-up signal. Cleaned up and all good now.

(I know the vans filthy, was a ex work van)

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View attachment 486917

Hats off to you for finding the fault, amazing