Csr intermittently not starting and stalling

[erictaavet]

Hello

I have encountered a problem with my 2004 B6 A4. Today, after a drive, I turned the car off for 20 minutes. When I went in the car again and turned on the ignition, no lights lit up on the dashboard. The car cranked fine but did not start up. Occasionally, when the ignition was on, the dashboard lights flashed on for a second. At one point the ignition stayed on - the dashboard stayed alive and I managed to start the car up. But after one minute the engine stalled in the middle of driving. When the lights on the dash flash on, I can hear many small relay clicking sounds. The car is stranded in another town, and I took a bus home to get my second car and a friend. What could cause this problem and how should I start diagnosing it. Previously, a little water has leaked into the plenum chamber where the ecu is located, which also caused some problems that I managed to fix. But that was 6 months ago. It seems like the problem is with the ECU, not the ignition switch because fiddling the switch seems to make little to no difference.
Video that shws the issue.
https://youtu.be/vm8pg1pblVQ
Has anyone had a similiar problem or knows how could I fix it.

Thanks in advance

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[Crasher]

The ECU relay or its wiring could be water damaged.

[erictaavet]

The car started up okay a few hours later. Only weird thing I noticed was that occasionally the interior lights (dashboard, all of the buttons) started flickering on and off. Also, Traction control light would come on and go off. Thirdly, the A/C would spontaneously turn itself off and on.

I opened up the plenum chamber and cleaned all the electrical connections with contact cleaners. I opened up all the relays and they looked fine, no signs of oxidation. Nevertheless, I bought a new 219 relay.

I hoped that it would solve the problem but a few days later, the ignition quit again mid drive. I noticed that the illuminated hazard light button flickered like mad when the problem ocurred. I could get the ignition to turn on for a second by activating any of the car electric components: hazard lights, blinkers, central locks. I uploaded a video of this problem: Electrical issues vol2 - YouTube
I also scanned the engine and instruments with VCDS and got the following fault codes:
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Also, one day when the lights started flashing and traction control turned on, I could smell some cables burning in the car. I could not pinpoint where the smell is coming from though. What else could cause these issues? Which module controls the interior lights for the buttons and dashboard.

[Crasher]

Have a look under the carpet on the cars left to see if it is wet.

[erictaavet]

Managed to fix the problem. It turned out that my alarm module in the drivers footwell was completely soaked and had oxidation all over the circuit board. Cleaned it with a special cleaner and a toothbrush and I am having no more problems.

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[Crasher]

That is what I expected, in left hand traffic countries it is on the passengers side.

[erictaavet]

The alarm module was filled with light blue water when I first discoveres it. I am wondering what caused the water to become blue. Does the alarm module have some kind of blue grease inside of it. What is the purpose of this?

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[Crasher]

Electrolytic oxides of Copper and other metals used in the solder such as Tin, from electrolysis across the power and earth due to the salts in the water which get in through the air intake under the windscreen, it turns a turquoise blue.