Disable headlight failure detection (VW up!)

Hello!

I could use your help with a VW up! GTI (Model Year 2022).

The goal is to disable lamp failure detection for individual light sources using long codes.
The problem is that while I can set the corresponding bits from 1 to 0, and the new encoding is accepted, the effect doesn't occur.
My question is therefore: Does this type of change require additional access permissions?

Background: In the vehicle mentioned above, the H4 light bulbs (high/low beam) were replaced from halogen to street-legal LED retrofit bulbs. Due to the lower power consumption (approximately 50%), incorrect error codes are being stored in the vehicle's control unit (roughly translated: high beam, short circuit detected, intermittently). This, in turn, results in the turn signal light being permanently deactivated. (Turn signal light: At night, when turning at speeds below 30 km/h, the inner fog light illuminates the inside of the curve to improve visibility.)

As I mentioned, what mainly interests me is the question of whether such a change requires some kind of additional "authorization" or approval. Or whether these changes are generally rejected by the StG due to any restrictions.

Best regards,
Frank.

There are two detections:
Cold diagnosis and warm diagnosis. As of 2010, only one of these functions could be disabled individually. The other function could only be disabled centrally for all light sources. I don't know if that's still the case today.

However, with a certified light source, no adjustments should be necessary. The error message regarding low power consumption only appears in my tests when the power consumption is below 5W. This makes it more relevant for parking lights rather than for low beam headlights.
The error message you mentioned (short circuit to ground) doesn't indicate too little current draw, but rather too much. This usually happens when there's a control unit with large capacitors present. I haven't encountered this problem with the approved light sources either.

I would contact the manufacturer of the light bulb. After all, they approved it for use in this vehicle. It's probably defective.
What is the exact manufacturer and model?

Thank you for the information. I wasn't aware of the distinction between cold and warm diagnoses. Learned something new again.

Okay, I was just checking the StG 09 - central electrical system in the car again. There are 4 error entries: one for the left and right headlights, and one for the high beam and low beam. "They all sound like this or something similar:"

Quote:

00978 - Headlight bulb for left low beam (M29) 010 - Intermittent interruption/short circuit after the positive terminal - Sporadic.

However, one thing that can be ruled out is a defect in the light bulbs. Currently, Osram Night Breaker LEDs (Gen 1) are installed. Previously, I was using Philips UltinonPro 6000 (Gen 1), which produced the exact same errors. According to both manufacturers, in my case, where the turn signal light no longer works after installation (due to the aforementioned error messages), corresponding "CAN bus" modules need to be installed. These are essentially large resistors that are connected in series between the LEDs and the connector. They then offset this "missing consumption" by wasting the entire energy-saving potential as heat.

While it's possible to suppress the error message, I absolutely don't like that approach. A more elegant solution would be to disable the headlight failure detection for high/low beam using VCDS. According to the currently used long coding, it should actually be disabled. Although I've reviewed all the bytes again, I haven't found a "global option" to disable the headlight failure detection. Not even in the adaptation channels. Or maybe I'm just not seeing it. :-/

Okay. A short circuit to the positive terminal actually indicates too little current draw. I must have misread "mass" the last time; it wasn't even there.

I cannot say what the coding options are for the 2022 model. Our vehicles are older.

Does the error appear immediately when the ignition is turned on (cold diagnosis), or only when the specific light is turned on (warm diagnosis)?

If the issue cannot be resolved through coding adjustments, you will likely need to incorporate a parallel current consumer. However, you could experiment with the resistors by choosing resistor values as large as possible, in order to dissipate as little power as possible.

Good evening, and sorry for the delay. The reason was that I recently replaced the aforementioned Osram Night Breaker LED (Gen.1) with the latest model from Philips, the Ultinon Pro6000 HL Boost gen2. (The new bulbs are simply two generations ahead and therefore better in every aspect.)

However, the problem remains that the lights are still causing errors in the control system (StG) due to their insufficient power consumption. That makes sense, because the new LEDs consume even less power, despite being brighter (more efficient).

After the replacement, I cleared the error memory. As long as the headlights were off, no errors were stored. However, as soon as I turned on the low beam headlights, the first two error messages for the low beam headlights appeared. Then I turned on the high beams, and the other two errors also appeared.

Okay, if the TÜV (German technical inspection agency) complains about something during the next vehicle inspection (HU/AU), then I'll have to check the resistors again. (Right now, the car's onboard computer isn't showing any error messages.)

Hello.
I drive a Skoda Fabia, model year 2020, and in the onboard network control unit (address 09), it's possible to adjust each lighting channel separately.
Perhaps it also works on the UP platform?
The easiest way is to save a snapshot of the control unit settings and then review the configured values beforehand.

Hello Fabollo,

In my first post, I already mentioned that I had set the corresponding bits in the StG (Steuergerät – control unit) to 0 (for low beam and high beam). "Nevertheless, errors are stored in the error memory ("short circuit to positive")." That's why my question is whether I need to consider anything else, such as an additional access permission or an additional (hidden "global") bit.

Here's a small update: Last month, I had to take my car for its mandatory technical inspection (HU) and roadworthiness test (AU). Prior to the inspection, I had to replace the LEDs with halogen bulbs beforehand (and clear the error memory), as agreed with the inspector.

That's why this topic remains relevant for me. While swapping the bulbs in my main headlights (H4) isn't a problem because they are easily accessible. The same goes for the fog lights (HB4), which are also on my wish list.

Best regards,

Hello,

It should be noted that software is not error-free. It's possible that the control unit doesn't even process these bits, as they are only relevant for vehicles equipped with incandescent bulbs.

Possibly compare part numbers if there's also a vehicle model with LED headlights.

Best regards, Rainer.

Hello Rainer,

Yes, I just had a vague hope that I might have missed something. But ultimately, it must be the case that these bits have no effect.

Unfortunately, the VW up! was not offered with LED headlights. As a non-expert, it's difficult for me to determine whether the StG is also used in other VAG vehicles, and even if it were, I wouldn't have the physical access to it.

The main problem is likely that not every individual light source in the up! can be edited yet. (For example, changing the left low beam bulb from halogen to LED.)

Thank you all very much for your help!

Best regards,
Frank.

Hello Frank.
It appears that your control unit uses the CAN protocol.
My UDS protocol and all the lamp channels are...
Is it readable as plain text, and therefore not directly comparable?
I definitely need to obtain permission before making any changes.
Enter the value for the control unit (VCDS suggests a numerical code).
And only then make any adjustments, otherwise it won't be accepted or saved.

Hello,
Unfortunately, the up! model isn't that modern yet. It doesn't have any of those countless lighting channels available in plain text. VW refrained from making the leap.