How to put LG G2 in fastboot mode?

Is there any way to get an **LG G2** (running the latest version of stock software, Lollipop 5.0.2) in **fastboot mode**? None of the methods listed anywhere online work for me. I'm getting the feeling that it's not an option on this device, but I've heard no definitive confirmation of that. Here's what I've tried and has not helped: - Turning the device off, holding down power and volume down buttons, releasing them when the LG logo displays, and holding them down again to power up. This brings the phone into Factory data reset mode, in which the only option is to Erase all user data & restore default settings. - Turning the device off, holding the volume up, and plugging a connected USB cable into the phone. This brings the phone into Download Mode. - adb reboot fastboot. This reboots the phone normally. - adb reboot bootloader. This also reboots the phone normally. (If you're wondering why I need to get into Fastboot: https://android.stackexchange.com/questions/110325/how-to-clear-caches-in-lg-g2-running-lollipop-5-0-2.) To be clear, I mean that fastboot devices lists nothing when I do any of the above methods. But adb is working.