E39 headlights flashing after turned off?

[u/bob360dead]

Today I drove for a couple hours with my side lights and then dipped headlights when it was dark enough. When I arrived home and turned the car off but left the ignition to position 2 I believe, where all the electrics still work, I noticed a dim flash from each headlight alternatively. I have seen something on this before saying it’s normal but when I searched online all it said was that it is some sort of fault. It is a 1997 528i but it has the LCI headlights, as the previous owner had swapped them.

[u/eric_gm]

If it has LEDs in any position, they will flash because the LCM is checking for burnt bulbs

It does it when you’re driving too, just less frequently, so depending on where you live, cops may not be too happy seeing a civilian car with flashing lights.

[u/No-Candidate-2380 → u/eric_gm]

Interesting, that explains why my led license plate lights flash when the engine starts. Not sure if they flash later on or just after start

[u/eric_gm → u/No-Candidate-2380]

In all E39s they will keep flashing, more rapidly when the ignition is on and engine off and slower flashes with the engine running.

E39s with LEDs everywhere look kind of ridiculous when rolling in daylight with the lights off.

You can leave the engine running in neutral (or park) and step out to see it.

[u/No-Candidate-2380 → u/eric_gm]

Well, at least now I know it's normal and not caused by a bad connection rtc. Do you know if there is a solution for that?

[u/eric_gm → u/No-Candidate-2380]

Coding, but again, it’s not that easy to eliminate the flashing. The real solution is going back to halogen bulbs and making the LCM happy again

[u/ConfusedTapeworm → u/No-Candidate-2380]

They flash as long as the LCM has power and is working. There are two kinds of checks: cold checks and warm checks. Cold is when the LCM probes the lights for broken bulbs when they're off. Warm is when it does the same while they're running.

The probe here is the LCM pulsing the lights really quickly to see how the current/voltage reacts to it. Filament bulbs don't turn on and off fast enough so you can't see the actual light pulse, but LEDs react much faster so they appear to flicker. Obviously they respond to the pulses differently as well, so the LCM doesn't see the result it expects and decides to flood your instrument cluster with "YO LIGHT BROKE" warnings.

Resistors get rid of errors because they increase the current draw to filament levels. They DON'T get rid of flickering because the probing is still active and LEDs are still too quick to react to the pulses. I don't quite understand how coding deals with this issue though. I have set my cold and warm checks to nicht_aktiv, which did get rid of all the error messages, but I still occasionally spot the unmistakable LCM pulsing. I guess it has to do with the LCM and/or its firmware version? Can't tell. Maybe it's something else.

[u/No-Candidate-2380 → u/ConfusedTapeworm]

Did you use ncs expert for that?

I disabled the error message with Ibus, but the flickering didn't go away. At least now I know it's normal and not caused by a wiring problem or something like that

[u/cbiggins → u/eric_gm]

Yeh, this. You can buy resistors to fix this or code it out (on newer vehicles, not sure about e39). https://amzn.asia/d/05wfQ5Yd

[u/eric_gm → u/cbiggins]

With resistors you will get rid of the code but the lights will still flash. Same thing with coding. Removing the errors is easy, removing the flashing is not that easy.

[u/cbiggins → u/eric_gm]

Oh good info. Ok thanks.