(I already posted about this in real time over at the M3OC forum, but seeing as it's a potential safety issue (see the bit below about the front turn signals not working) and more generally just a PITA, I thought I'd share it here too...) Last week while parked in my Model 3, I hit the "Adjust Headlights" button in the Service menu, and that caused the car to get stuck in some kind of service mode. (I'm on firmware version 2018.28.5.) The effects of this were the following: The daytime running lights stayed on permanently, even when the car was off. The headlights could not be manually turned off, and after the car was off they would stay on for about an hour, then cycle off for an hour, then back on for an hour, and so on.) The front turn signals did not work. (This was of particular concern since there was no indication to the driver that they weren't working, so I drove around for days without working turn signals without realizing it. It's not hard to imagine this leading to an accident.) The high beams did not work. The interior ambient lights could not be turned off. The dome lights would not turn off when in "Auto" mode (but they could be turned off by switching the setting to "Off"). Significantly higher than normal vampire drain -- probably partially from the lights themselves, but also likely from the car not going to sleep. I went through all sorts of troubleshooting steps while on the phone with customer service including resets and shut downs, but nothing worked. 6 days later Tesla finally sent out a mobile repair tech. He mentioned he had seen or heard of a couple other instances of this happening to Model 3's. He did a "hard" reset by disconnecting the 12V battery and a connector to the HV battery BMS for a few minutes, and that did the trick to fix it. So, long story short, I don't recommend pressing the "Adjust Headlights" button. If you want more details, check out the link at the top.