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21 Posts
Have there been any developments on this issue? I am experiencing these exact symptoms with my 2005.5 Jetta on the rear left blinker, AND right front parking light. For several months it followed temperature--hot days it wouldn't work, cold days it would. Now it pretty much just doesn't work ever. Pulling and reseating bulb makes no difference. Replacing bulb makes no difference. Pulling and reseating wiring also makes no difference.
I attempted some basic troubleshooting one day, and it seems like VW in their infinite wisdom decided to program the canbus system so that when a bad bulb is detected, it immediately disables power to that bulb. To test this theory I pulled out a working bulb from the opposite tail light while it was lit, and when I reinstalled the bulb it did not light until I turned the ignition off and back on. This is great in theory, to prevent damage in case of a short or something, but how the heck can you get out your multimeter and troubleshoot the circuit if no power is being applied to it? Can anyone confirm/refute my understanding of this? And if that is true, does anyone know of a way to override this "feature" with VCDS or otherwise for troubleshooting purposes?
Also, does anyone have a diagram/schematic showing the lighting circuits? It would be nice to know where the wiring runs, where the relay is, where the module is that controls lighting (is it the body control module???), and if there are any other devices wired in the circuit that could have failed.
I attempted some basic troubleshooting one day, and it seems like VW in their infinite wisdom decided to program the canbus system so that when a bad bulb is detected, it immediately disables power to that bulb. To test this theory I pulled out a working bulb from the opposite tail light while it was lit, and when I reinstalled the bulb it did not light until I turned the ignition off and back on. This is great in theory, to prevent damage in case of a short or something, but how the heck can you get out your multimeter and troubleshoot the circuit if no power is being applied to it? Can anyone confirm/refute my understanding of this? And if that is true, does anyone know of a way to override this "feature" with VCDS or otherwise for troubleshooting purposes?
Also, does anyone have a diagram/schematic showing the lighting circuits? It would be nice to know where the wiring runs, where the relay is, where the module is that controls lighting (is it the body control module???), and if there are any other devices wired in the circuit that could have failed.
