[Solved] Disable Cold Bulb Check for LED Low Beam on Skoda Octavia Mk2 PQ35 Platform

I changed low beam lights for LEDs on octavia mk2 (also sometimes called 1Z or A5) (no led h7 bulbs, but LED projector retrofit).
Car is based on PQ35 platform.
Issue is that there is cold bulb check when key is moved to ignition is on or accessory position. Most times this results in error about one or both headlights having light bulb not working.
So far I have tried:
looking in VCDS and there is no way to disable cold bulb check for low beam
VCP - this has option to program BCM eeprom, options for every bulb to disable cold bulb check EXCEPT low and high beams
Vaghelper - this is basically what VCP copied
I have added capacitor into one headlight and it seems to eliminate the error. but every time I turn on the car headlight does flash as it does the cold bulb check, which is kinda embarrassing. It does so even without the capacitor, but very dimly.

from the ELSA it seems that BCM pins they cold bulb check need to be disabled are A11 and C52.

Is there a known way to program BCM to not do cold bulb check for low beam?
Is there known hardware workaround that would get rid of the error and not cause headlights flashing?

I had a similar problem on my SAAB 9-3, error and LED flickering. So you can make a simple RC delay (10-15 ms) circuit which has one MOSFET and 4.7-10 Ohm resistor turned on for 10-15ms when the pulse appears to simulate halogen bulb and second MOSFET, which will turn on main/dipped beam LED after 10-15ms to avoid LED flickering.

Not that easy for me to make circuit like that, that would be ideal solution, i hoped someone might make thing like that commercially available. If I keep the car I want to make timer delay that would disconnect ground for about 2 seconds between headlight and capacitor so that would hopefully get rid of the issue with blinking after startup, but what you describe is much more elegant as it does not need additional taps to fuses etc. and is just wired H7 - circuit - H7 so same as the the capacitor I currently use (in my mind it is better solution to fool BCM bulb check then resistors - well at least when wired constantly).

I do not even know how I would go about doing the 15ms delay with discrete HW, I do only know how to maybe do it with MCU - that adds bootup time, complexity, etc.

EDIT: I searched a bit about RC delay, so guess I need to do some learning https://en.wikipedia.org/wiki/RC_time_constant

Give me some time and I'll post a circuit I made here. It was a long time ago, need to find it on my drives

I struggled with this on my Audi A3 - it's also VAG and VCDS.
Initially I went down the same route as you and the effect was identical - an annoying flashing three times when the ignition was switched on. The solution turned out to be simple: I found a point in the VCDS that switched the halogen bulbs in the headlights to LED and the problem disappeared, with the burnt LED bulb being detected correctly. But where was this point? - Kill me and I can't remember. It's been a few years now.

This is what it looks like https://youtu.be/ujsb7J0VzF0

There is nothing like the LED in the headlights in VCDS for the BCM PQ35.
Even VCP does not have the correct pins in the EEPROM Wizard editor.

You probably have a newer car, so a different platform.

I don't know how helpful this is or how to judge the similarity of our cars, but I had a spare moment today and sat down on VCDS to find what I changed. And I found it. So I am posting - but how much it will help you I don't know....
.
I had the same symptom as you: after turning on the ignition a few flashes in one headlight, immediately afterwards the same in the other. After changing the parameter "like a hand, it went away".

I decided to put a 10s timer relay ( https://www.aliexpress.com/item/1005005956224821.html ) fed from the engine fuse box that comes on with ignition using "add a circuit" and just run it to the correct pin on the headlight input using an extension (https://www.aliexpress.com/item/4000310812794.html < this one was my case, but if you are using xenon housing you will have this > https://www.aliexpress.com/item/1005007720420214.html) - since I do not like cutting or slicing original wires, even on such an old car.
I'm not 100% sure now, but I think I used fuse 18, where no fuse was plugged, but it came live with ignition.
This way there is also no need for the capacitors that did get rid of the bulb out error.

It would be super easy to do on other cars that use relays for headlights, but it seems in Octavia 2 power is controlled directly from BCM?
Or one could probably still alter BCM EEPROM, but I could not figure out how exactly to do that as I was unable to find out what pin corresponds to which address.
Or another possibility, which I was too lazy to research, but makes sense to learn in the long run, would be to send a CAN message to turn on headlights and then to turn them off from the ESP32 board (if not commanded on by bcm (light switch) ).

Anyway today I wen to local equivalent of MOT/TUV - STK I do not know if in Poland you call it BTP? And they did not like the flashing.

Since my last post I found out that it does happen when you turn the car off and then on shortly. No idea how to get rid of this now. I'm guessing it is something related to the fact that during cranking car does disable accessory power.

I figured older VAGhelper can decode VCP exported HEX string to the corresponding pins in bcm - but asi zou can see neigher A11, nor C52 is there so I do not know if it is VCP export at all maybe this export is some predefined addresses just put right one after the other and not just som "FROM TO" part of BCM eeprom



So seems to me, that issue is that VCP and VagHelper only export byte18, while the config for the pins i need is somewhere else :/ (byte18 is what vcds tells you not to change basically ever )

Sorry I still do not understand how elektroda translates posts if you should write in Polish or english.

So there is one exact combination of xenon settings that makes everything work in VCDS
14-3
17-2
25-2
this way - no cold bulb check (I did not test hot bulb) for low beams and high beams, still high beams turn on, even automatically when lights are set to auto and even the halogen high beams do work in conjunction with bi led shutter. Even the lights signal to the radio and interior lighting works correctly.

Another update - for cars with factory DRLs you can set xenon without active shutter in screen 14 as xenon shutter uses same pins on BCM as the ones used for DRLs on halogen cars.