LED front signal bulb error

[lucius]

Hi, long story short, I changed my golf mk7 front headlight singal bulbs to LED (non-oem), then I have received a warning on the dashboard 'check bulb error'. Also, for my partner's car Polo AW MK6 (OEM headlight is halogen unit), she bought an aliexpress LED headlight unit (with LED dynamic turn signal), she has the error code showed up when using indicator, hyperflash singalling in the dashboard, but the signalling pattern is normal in the indicator bulbs (weird)so I am guessing codings needed to be done too? 

Could someone here can kindly guide my how to code the bulb type to led please? I have done some researches that I believe Leuchte 0 and Leuchte 1 referring to the front indicator (left and right), but then when I clicked the button, there are so many options which I was not sure which one to change? Some posts saying changing the type of load, and some saying changing the number from 50 to 0 of Fehlerort_mittleres_Byte_DTC-DFCC will do? 

Thank you in advance for the helps and I really appreciated. Please see attached pics for the options to click in the obd11 app.

Attachments:

[dv52 (Australia)]

lucius : Hi.

Try this on the Golf:

Leuchte 0 BLK VL B36 and Leuchte1BLK VRB20

• Lasttyp > 38 LED Blinkleuchten
• Dimmwert AB > 127

I'm less certain about the Polo because the retrofit involved both a change to LED lamps AND a change to dynamic turn signal. Normally dynamic turn-signal fittings require a separate power-supply to energize the internal LED "chaser" circuits. Because the new fittings were non-OEM, every different 3rd-party manufacturer does this differently. When the new fittings were installed was this done? What were the manufacturers coding instructions for the dynamic turn signal fittings?

Anyhow, you could try my Golf tweak above on the Polo too!

Don

[lucius]

Hi Don dv52 (Australia)

Thanks for the help and I appreciate it, just out of my curious, changing the Lasttyp to 38 LED Blinkleuchten is to let the control unit know LED bulbs have been installed, but whats the purpose of changing the Dimmwert AB from 100 (orignal setting) to 127 as you suggested.

When the new fittings were installed was this done? What were the manufacturers coding instructions for the dynamic turn signal fittings?



The fittings were done last week, the signalling flow looks fine as normal outside the car (polo), the only problems she experiencing are check bulb error code and hyperflash on the dashboard, not sure about the coding instructions as sellers didnt mention, but I will ask the seller to see if they have guidlines.



Lucius 

[dv52 (Australia)]

Jun 18, 2024 9:58:41 GMT lucius said:

.................just out of my curious, changing the Lasttyp to 38 LED Blinkleuchten is to let the control unit know LED bulbs have been installed, but whats the purpose of changing the Dimmwert AB from 100 (orignal setting) to 127 as you suggested.

Lucious: "Yes" to the first part of your question.

The answer to the 2nd part of your question is a tad more complex! Are you familiar with an engineering principle called "Pulse-Width-Modulation" ?

If not, it's the system used by the central electrics module for managing the illumination levels of the 35 x exterior lamps on MQB platform cars

Below is an extract from my recent reply to a very similar question from another forum colleague:

Jun 17, 2024 9:11:12 GMT dv52 (Australia) said:

................At the heart of the answer is an engineering principle called Pulse Width Modulation (PWM) - which is the system that is used to dim lamps to different levels. You might think that a lamp on this car is dimmed by applying a lower voltage to the lamp but this is NOT what happens (well, not directly at least)

What actually happens for lamp dimming is PWM. This is the process whereby electronic circuits inside the module chop-up the battery rail voltage by rapidly switching the 12Volt supply ON/OFF  to create a square-wave. The ratio of the ON-time and the OFF-time of the square wave determines the dimming level. This ratio is called the "duty cycle". Here's some examples of PWM with different duty cycles:

Hopefully you can see that feeding a lamp with the 3 x wave forms above will change the dimming level of the lamp. Increasing the ON-time compared to OFF-time in the waveform will make the lamp brighter and vice-a-versa. PWM does change the "effective" supply-voltage to a lamp - but it does this in a far more efficient manner with much lower power/thermal loss!

When you used Leuchte-programming to change the Dimmwert values in my suggested tweaks - you actually changed the duty-cycle of the PWM waveform that supplied power to the lamp.

The central electrics module on this car can use a different form of PWM to separately control LED lamps and halogen lamps. VW designed the module in this manner to increase the efficiency of the power-supply for the many lighting functions that Leuchte-programming can deliver.

I call VW's PWM method for halogen lamps "analogue" control because the Dimmwert value range is 0 ->100, whereas I call PWM for LED lamps "digital" control because the Dimmwert value range is 0 -> 127.

I use the term "digital" for LED control because a total of 128 x different dimming states is the highest quantity for a 7 x Bit binary number (yes, this discussion is a bit geeky).

Halogen lamps can tolerate PWM well without many problems - but LED lamps are not so tolerant and often the semiconductor in the LED lamp requires very strict PWM characteristics to operate properly. The other problem is that there are a huge number of manufacturers of LED lamps - each making non-OEM lamps with different operating characteristics! That's why retrofitting non-OEM LED lamps into a mk7 can sometimes result in error messages!

Hopefully the extract above answers your question - if not, I'm happy to elucidate further

Don

[lucius]

Hi Don dv52 (Australia),

Thanks for the explanation although it's sort of complicated to understand haha, I have followed your instructions exactly the same as you suggested for golf, it works perfectly fine! For the Polo AW, I have just changed Lasttyp to 38 LED Blinkleuchten, Dimmwert AB stayed the same as 100, so far no error codes come up and no hyperflash, everything seems normal. Would you still suggest me to change the value to 127 as my partner got the aliexpress LED headlight unit with led dynamic signal, or if the existing setting works then just leave it?

Once again thanks for your meaningful help, really appreciate the help you offered for this forum!

[dv52 (Australia)]

lucius : Good that you have fixed your issues - well-done!

So, with regard to your specific question (and as I wrote in my failed explanation on PWM), when you changed the lasttyp channel-value on the Polo to an LED setting - you told the central electrics module to start using "digital control" to manage the front turn-signal lamps.

The LED system of PWM-control permits greater granulation when choosing the dimming level of a lamp because the dimmwert value has up-to 128 x steps. If you leave the dimmwert value at 100 on the Polo, it simply means that the turn-signal lamps will be at 78% of full illumination (i.e. 100 divided by 128). Of course, this illumination-level only happens in the ON-part of the blinking cycle!

These non-OEM lamps vary greatly in performance - so I have no idea if there is a visually discernible difference between 78% illumination and full illumination on your chosen lamps!

It's entirely your choice how to proceed - but I suggest that you try the value 127 and make your own judgement (you won't break anything and you can easily return the value back to 100 if you so decide)

Don

[lucius]

Hi Don dv52 (Australia),

No worries and thanks for the help!

Lucius