Struggling with N199 airbag igniter fault 01217

[VAG-Abound]

This is actually on a 53 plate Touran, but I expect there will be plenty of useful insight from the Mk 5 forum which shares much of the platform...

Long story short is that after a good half-day of investigation I'm no closer to understanding why the car is showing fault 01217 and "Upper Limit Exceeded" against the N199 driver airbag igniter, and the wiring loom that plugs into the J234 is confounding me

I'll try and describe the problem and investigation so far in the hope that someone can spot what I've missed, give other pointers, etc.

In hopefully the right order (BTW, battery detach and VCDS reset after each relevant stage)...

1. Car started showing airbag warning light. I reset it a few times with VCDS, but it comes straight back on. Car has now failed MOT on this.
2. Had a look around various forums and figured out which connector is involved. White / green / brown wired one under driver's seat.
3. Tried detaching, reattaching, cleaning. No change.
4. Tried putting 1.2 Ohm resistor across green and white. No change.
5. Found equivalent white / blue / brown connector on passenger side. Detaching this causes same fault for N200 module. Putting resistor in place overcomes igniter fault there, but leaves one for occupancy detector.
6. I think that confirms I'm working on right plug, and that resistor trick should work on each side. Is that a reasonable belief?
7. Start to think that as connection through to driver seat plug is broken somewhere. Found couple of variants of this diagram showing how seat connectors reach back to J234 airbag controller.
8. Opened up under radio / heater area to get to J234. Removed (nominal) 75-way connector from controller.

This is where it gets odd...

1. Used numbering on that diagram to test loom connectivity from J234 through to seat plug points.
2. Delighted when on passenger side pin 27 has connectivity to blue under seat. Just as expected.
3. Whenever I get an expected connection I test for false positives by trying something I expect to be open circuit. So I was confused upon finding that pin 28 also has connectivity to seat blue.
4. Found that 27 and 28 at controller have connection to both blue and white at seat. Very confused as to how this can be if resistor works across there.
5. Even though passenger side was confusing thought I'd see if there was anything to find out on driver side. Turns out to be same, in that pin 29 and 30 plus green and white at seat all connected.

Somewhere along the say I found a reference to this "sub-loom": Volkswagen Touran (2003 - 2005) - adapter wiring set for seat base. > VAG ETKA Online > Nemiga.com, which presumably connects into the loom back to J234 at some point. I'm thinking of looking for where that connects to see what is happening there, but am not sure where to find that and don't really relish taking whole cabin apart when the way the passenger side is connected (but working normally) leaves me unsure what I'm really trying to find .

Anything else I should try / inspect?

[VAG-Abound]

My errors were here...

4. Tried putting 1.2 Ohm resistor across green and white. No change.5. Found equivalent white / blue / brown connector on passenger side. Detaching this causes same fault for N200 module. Putting resistor in place overcomes igniter fault there, but leaves one for occupancy detector.

Realise overnight that I'd used 1k2 resistor . Suggested value other threads / for a is ~2 Ohm. No idea why passenger side is happy with that, but it was very misleading!

I didn't have any low vale resistors to try directly, but remembered from school days that carbon / graphite can be used for this sort of thing . I grabbed a couple of circuit prototyping jumper leads to push in the end of the car-side loom, and "wipe" along a spare refill lead from a propelling pencil (confusing mixed used of "lead" in there: first is as in "electrical lead", second as in "pencil lead" / "lead weight"). Sure enough the measuring blocks go from "Too High" to "Correct" and then "Too Low" as I bring the wires closer together while pressed against it.

All in all seems like car side of loom is fine .

I've just popped to Maplin to get a few low value wire-wound resistors to try and test more, and am expecting to work on the airbag cable / plug to see if there is a bad connection in there and how to overcome it.

[VAG-Abound]

I've just popped to Maplin to get a few low value wire-wound resistors to try and test more, and am expecting to work on the airbag cable / plug to see if there is a bad connection in there and how to overcome it.

I tried a few resistor values plugged into the car side of the wiring to find out what worked by watching the measuring blocks:

1.1 Ohm - Too Low
2.2 - Correct
4.4 - Can't remember
5.5 - Too High

With the 2.2 Ohm I can clear the faults and they stay cleared .

I then snipped the white and green on the disconnected airbag side (so no connection on those to actual airbag unit at the mo), put the 2.2 Ohm resistor on there with a bit of chock block and plugged it back in to the car side. Still "Correct", so (famous last words) that seems to rule out total conductivity failure on the connector, although at these low values a poor connection might just be pushing things over for a healthy airbag unit.

Ran out of daylight and warmth, so I'm going to rub around with it like that for a few days and see if it stays clear of faults. I'm thinking about removing the connector units completely, but don't want to do that only to find that there fault returns and it is actually in the airbag module after all. If it's headed that way I'd prefer to be able to push it back in on the original connector. "Proper" removal seems to be with extensions and splices, but I'm thinking of using good quality bullet connectors to allow easier demount if event needed again.

Does anyone know how often this fault is actually caused by the airbag module rather than the connector?

[VAG-Abound]

Ran out of daylight and warmth, so I'm going to rub around with it like that for a few days and see if it stays clear of faults. I'm thinking about removing the connector units completely, but don't want to do that only to find that there fault returns and it is actually in the airbag module after all. If it's headed that way I'd prefer to be able to push it back in on the original connector. "Proper" removal seems to be with extensions and splices, but I'm thinking of using good quality bullet connectors to allow easier demount if event needed again.

Does anyone know how often this fault is actually caused by the airbag module rather than the connector?

Found a few minutes to snip out the original connectors and put a more direct connection between the wires in place. Error came back straight away .

From the links I posted above I wonder if the "upstream" connector could have a high resistance causing the problem, or whether this indicates that it is the airbag. AIUI the light won't stop the bag working (as long as it isn't completely kaput), so I'll leave it as is while I try and figure out how to test / replace airbag module.