Resolved VW Crafter with Airbag fault codes

[Aldervai]

Hi folks,

I have a 2016 VW Crafter with the two following fault codes -

9241 - Driver Safety Belt Tensioner Igniter (N153): Resistance too low
9250 - Front Pass. Safety Belt Tensioner Igniter (N154): Resistance too low

I've removed the door pillars and inspected the tensioner connections. When I disconnect a particular sides connector, that specific code changes from resistance too low, to resistance too high.

Also, the VCDS shows an additional code that's a little worrying -

9023 - Central locking: emergency opening activated: msg from elect. ign/starter switch

The van did have some water ingress, and I found a forum post elsewhere regarding a VW Transporter that describes the same codes, which was caused by a water damaged ECU which was under the seats.

On a crafter it is listed as under the front console, which would be a royal pain to remove.

Does this sound like a vehicle that suffered a front end shunt? There are other factors that make that unlikely, but not an impossibility. It's the fact that the sensors move from low to high resistance when unplugged that has me thinking its two fired seatbelts. Anyone have any ideas it would be much appreciated?

 

[Dr Sheldon]

I've removed the door pillars and inspected the tensioner connections. When I disconnect a particular sides connector, that specific code changes from resistance too low, to resistance too high.

That is valuable knowledge !!

For sure we now know that all the wiring to the Belt Tension Ignitors is good, Airbag Module is good, the DTC reporting is accurate, VCDS is reading the system corrrectly.

What is left ? Both Seat belts need replacing, they likely have been ignited in a collision.

 

[Dr Sheldon]

It's the fact that the sensors move from low to high resistance when unplugged that has me thinking its two fired seatbelts.

Exactly that !!

 

[Uwe]

Both Seat belts need replacing, they likely have been ignited in a collision.

How does an igniter's resistance get lower after it has been fired? I would think it would be open circuit after having been fired.

Do these tensioners have shorting bars in their connectors to prevent static from unintentionally firing them when they are disconnected?

-Uwe-

 

[Dr Sheldon]

See if can unravel this Conundrum !!

How does an igniter's resistance get lower after it has been fired?

It does not go higher or lower - The Ignitor remains the same. As in my Electronic Cigarette lighter !

Being pedantic then as it fires the heat will have some negligible effect on Resistance - That would be momentary ?


That is making the assumption that the Ignitor, when fired, will melt and destroy itself. That there would be a design built with very fine tolerances. There would be no way for the ECU to know or guarantee it has effectively fired the pyrotechnic ?

OP is promoting change by unplugging them !!!

I personally would put a Variable resistor in there to prove the Wiring & Module Reaction !


I dont believe it goes Open or High ? Neither do i think the "element" destroys itself.

I think as it ignites and mechanically pulls the belt back a connected mechanical device moves and shorts the 2 wires in there permanently forcing a short circuit - Low or No Resistance - Confirmation that that it has fired and it has functioned mechanically and then a DTC that will never clear rendering the belts useless.

Do these tensioners have shorting bars in their connectors to prevent static from unintentionally firing them when they are disconnected?

Yes Correct.

• When Unplugged the ECU cannot see the "Shorting Bars" they are in the seat belt ? Detached !
• When plugged in the ECU still cannot see them as they are pushed out of the way ? No longer part of the circuit.

Those shorting bars have no contribution to make in this thread or diagnosis ?

 

[Dr Sheldon]

Does this sound like a vehicle that suffered a front end shunt? There are other factors that make that unlikely,

No! Seat belts are the first thing to go off !! Have heard stories where a good Pot hole can pop them.

 

[Uwe]

The Ignitor remains the same. As in my Electronic Cigarette lighter !

There's a big difference between a cigarette lighter and a pyrotechnic igniter. The former is intended to be used over and over again, likely designed for thousands of cycles, and it's acceptable for it to take several seconds to get hot enough to do its job. A pyrotechnic igniter on the other hand needs to work "instantly" (within miliseconds), but it only needs to work once. If you put enough energy into a tiny bit of metal to heat it that fast, chance are you will destroy it, because you won't know when it has done its job, i.e. you won't know when to stop applying power until the circuit opens. Thus my expectation that a blown igniter would show open circuit or Resistance too high, not Resistance too low.

Those shorting bars have no contribution to make in this thread or diagnosis ?

Unless there's something that's preventing the shorting bars from un-shorting when being plugged in, in which case you would indeed see "Resistance too low" when those belt tensioners are plugged in and "Resistance too high" when they are not.

-Uwe-

 

[Dr Sheldon]

Unless there's something that's preventing the shorting bars from un-shorting when being plugged in,

They are Cleverly designed. If they were deformed then it would make it hard if not impossible to attach the connector and lock it in place.

If the bars were missing then in this case we have a moot point. The thing could accidently be deployed but not cause OP 's fault.

cigarette lighter and a pyrotechnic igniter. The former is intended to be used over and over again, likely designed for thousands of cycles,

Agreed

If you put enough energy into a tiny bit of metal to heat it that fast, chance are you will destroy it,

That depends on its design and construction ?? There maybe a resistor in Parallel in there. Should the Ignitor melt then resistance would be lower ? That lower resistance reading being confirmation that the Ignitor element is no longer there.

With the resistance in there only being ~2.5 ohms it maybe that the Ignitor detonates a small charge which in turn makes the Bigger Bang ?? From my training days I do know that a capacitor is used to fire far more than battery Voltage in there - I seem to recall figures between 40 - 60v.
As a side note I have popped these devices with a 9v battery. I am thinking the Higher Voltages would enable faster, more precise, powerful detonation ?

because you won't know when it has done its job, i.e. you won't know when to stop applying power until the circuit opens.

My theory is that it will know when it has deployed, and over the entire scope of its movement because a mechanical device is in there that will move / slide alongside the belt retraction mechanism and short the two wires causing low or no resistance.

@Uwe - This is not beyond the realms of possibility or probability ?


Hopefully OP can swing by and do some simple testing to enlighten us on our equally plausible theories.

I am both stupid and clever enough to measure the resistance of the ignitors using long wires and a secure container having paralysed the "shorting bars". I deem it unwise to ask OP to risk life and limb to do so.

 

[Aldervai]

No! Seat belts are the first thing to go off !! Have heard stories where a good Pot hole can pop them.

This is really interesting. Thanks Sheldon and Uwe for the comprehensive discourse. I am going to see if I can probe the seat belt ignition connector with a multimeter and test the resistance, whilst releasing the shorting bars. If I understand correctly, it should read between 2-3 ohms if operating correctly.

If it were just one side giving an issue, I would consider a faulty connector or similar issue. However, as it is both sides, and both show resistance moving from low to high when unplugged, I have a strong feeling it's both belts have fired.

I will update with the resistance readings if I get them. So far I haven't found a code or message that would definitively indicate that the seat belts did indeed go off.

 

[Dr Sheldon]

I am going to see if I can probe the seat belt ignition connector with a Multimeter

DO NOT DO THAT !!

They are not to be tested with a meter !!

You DO NOT know that they have deployed or not !!

They have the Potential to cause harm !!

What you can do is put a 2.5 ohm resistor in the plug and see if the code clears.

So far I haven't found a code or message that would definitively indicate that the seat belts did indeed go off.

You wont get that !!

Usually if the have deployed you can see it and the belt will be all saggy and horrible. Alternatively you may have 2 faulty ones ?

Did you buy that way ?

Are you the only driver ?

What is the story to this fault - How has it come about ?

Thanks Sheldon and Uwe for the comprehensive discourse.

@Uwe

Well he hurt my head with those challenges -Bordering on Mental Health issues

 

[TTT]

I’ve heard / seen others testing airbag systems with multimeters. Man, these people just don’t have a clue what they’re playing with. Just no clue.

 

[Aldervai]

Found this video and the guy seemed content with using a meter on the connector, but will take your heed and leave it be. Don't have a 2.5ohm resistor to hand but will get one ordered.

Man, these people just don’t have a clue what they’re playing with. Just no clue.

Happy to take advice, and I understand that there is an explosive charge inside which rapidly retracts the seat belt as per design.

I am a qualified engineer and understand both mechanical and electrical systems to a relatively high degree. I planned to test as Sheldon described, with an isolated container and long wires before using the meter.

What is the story to this fault - How has it come about ?

The van has been used by a friend during my ownership. It's in the middle of a camper conversion, and had some water ingress due to a faulty fitted skylight. I had though there was some merit from this thread where the OP discusses water damage of the Airbag ECU causing the same codes to appear. But that was on a Transporter.

Air Bag woes!! Airbag light stuck on and due MOT! :(...

Hi,i have a vw transporter t5 (t30) that has issues with the air bag system. vcds faults; 3 faults found 00588-airbag igniter,drivers side (N95) 33-00- resistance too low. 00654- seat belt tensioner igniter;drivers side (N153) 33-00-resistance too low. 00655- seat belt tensioner igniter...

www.vwt4forum.co.uk

 

[TTT]

There is a reason why that guy’s last video was 10 years ago! Last he saw was a flash?

 

[Dr Sheldon]

So far I haven't found a code or message that would definitively indicate that the seat belts did indeed go off.

Some cars / vans will record Crash Data and some dont - it is a lottery ! Plus we have the so called "Diagnostic" monkeys out there that make light work of clearing that Crash Data

 

[Dr Sheldon]

Don't have a 2.5ohm resistor to hand but will get one ordered.

https://www.amazon.co.uk/dp/B079Z7VHBG

 

[Aldervai]

There is a reason why that guy’s last video was 10 years ago! Last he saw was a flash?

ha, fair point.

Thanks Sheldon, I'll get that ordered. Will report back what I find. If I don't, maybe I went in a flash.

 

[Aldervai]

Usually if the have deployed you can see it and the belt will be all saggy and horrible. Alternatively you may have 2 faulty ones ?

Ah I forgot to mention. Both belts work fine, as normal. The van didn't have these dtc's several months ago. The airbag warning appeared in the dash while the van wasn't being used. Hence why I'm thinking it may be a water ingress issue similar to the transporter issue the other guy had. I'll see how things go.

 

[Uwe]

I am going to see if I can probe the seat belt ignition connector with a multimeter and test the resistance, whilst releasing the shorting bars.

Like the good Doctor, I would advise against that.

If they've not been fired, you risk firing them by doing that. I don't think that's as big a risk to your personal safety with belt tensioners as it would be with actual airbags, but still...

-Uwe-

 

[Aldervai]

In conclusion, the issue was indeed that both seatbelts had fired. So there we go. Fixed by replacing the full belt units and clearing the DTC's. Job done. Certainly a strange one. Thanks for the help and discourse folks. Very much appreciated!