Airbag Polo 6R

Hi,
The AI system in our Polo is displaying the airbag system warning light, and the diagnostic tool is reporting an error.

9445417 - Key switch for deactivating the passenger-side airbag.
B1020 29 [136] - implausible signal.

I had already deleted this error (sporadically, once) about a month ago. The passenger airbag on/off status, controlled by the key switch, is correctly displayed on the dashboard indicator.
In discussions found in the deep web, the only cause identified for this issue is a faulty key switch, which can be resolved by replacing it.
Swapping the E224 wouldn't be a problem, but I wanted to ask about it here first.
hg
Herbert.

As far as I know, the key switch has two sets of contacts, and the signals from these contacts are likely monitored for plausibility. If, for example, one-sided resistance develops in one of the contacts, that could be the cause of your problem, and replacing the switch would be the solution. Therefore, I would also start by replacing the switch.
How old is the Polo?

Year of manufacture: 2011. The key switch (E224) internally connects two inputs from the airbag system to two resistors in series with ground. Depending on the switch position, one of the two paths alternately bypasses the ground-side resistor. The switch contacts are double-contact.
In this particular case, the switch was actually never used.
I'm going to try replacing the switch.
hg
Herbert.

What do you think about cleaning the contacts and applying contact lens solution to them?
Perhaps the problem is simply dust and/or an oxide layer on the contact material.
It's still worth a try.

"Contact cleaner" sounds good, but I once ruined the rotary switch of a multimeter with a common, aggressively cleaning "contact spray": after a few weeks, the formerly copper-colored contact pads were dark gray to greenish due to corrosion. I couldn't get the multimeter working properly anymore -> scrap.
Since then, I've avoided using contact cleaning sprays. Slightly corroded switch contacts, which return to normal operation after a few dozen cycles (hopefully removing the corrosion layer in the process), I now only treat with a non-acidic spray lubricant.

I propose "Wellenschalteroel K" (red) as a keyword.
It may be known under different names in the West.

I replaced the switch. Let's wait and see if this finally resolves the issue.
Regarding the internal components: it's a small circuit board with four SMD resistors and two miniature toggle switches from Cherry (automotive subsub DJ), which are operated in parallel. There's definitely nothing you can do to modify it. Besides that, in an airbag system circuit, I would only replace parts, not attempt any internal repairs.
hg
Herbert.

Hello everyone!

Herbert wrote:

... Besides that, in an airbag system circuit, I would only replace parts, not attempt any internal repairs. hg Herbert

I see it exactly that way, and no other way .
Somewhere, there has to be a limit to the combination of stinginess and playfulness.

Best regards from Munich!

Sure, I can provide pictures of the switch's internal components if you'd like.
hg
Herbert.

I can see cold solder joints, even in your photo .

Mark what you mean, and I'll take a closer look with my magnifying glass.
hg
Herbert.

In the area of 2.7 cm, a cold solder joint is particularly visible at the central of the three solder joints.

I can't see anything on the part itself. The tin surfaces are slightly discolored, but that should be due to age.
hg
Herbert.

I also think that the way the three contact pins are soldered looks strange. "Could you please take a picture with the flash on?"

You can see more in a blurry picture taken with a mobile phone than I can with a magnifying glass.
In this specific case, the warning light illuminates and remains on due to a single, intermittent fault. After experiencing this issue twice, with a significant time interval between occurrences (twice in 8 weeks), I replaced the switch. Further investigation is not worthwhile; it would be purely academic. I just want to get rid of the problem.
hg
Herbert.

Hello everyone!

@HerBärt: As mentioned above, I would strongly advise against tinkering with areas that are absolutely critical for safety, such as the airbag system and related components.
In my opinion, switching the switch was and is the only sensible thing to do!

...however, the solder joints look really cold and further indicate the use of low-quality/oxidized solder by the manufacturer (due to cost-cutting ).

If you (for us) would like to take the trouble and the vehicle is mainly used for solo operation, it would be interesting to re-solder and test a temporary reinstallation .

Best regards from Munich!