Based on the symptoms you described, it sounds like your Lenovo ThinkPad T470 may have a hardware problem. The fact that the fan and keyboard backlight turn on but the LCD screen remains blank suggests that the problem may be with the LCD itself or with the cable that connects the LCD to the motherboard.
If you have access to another ThinkPad T470, you can try swapping the LCD screens to see if that fixes the problem. If it does, then you know that the problem is with the LCD screen. If it doesn't, then the problem is likely with the cable or with the motherboard.
If you don't have access to another ThinkPad T470, you can try contacting Lenovo support for help. They may be able to diagnose the problem over the phone or they may send you a replacement LCD screen or cable.
Here are some additional troubleshooting steps you can try:
# ***Check the LCD cable.*** The LCD cable is the cable that connects the LCD screen to the motherboard. If the cable is loose or damaged, it can cause the LCD screen to go blank. To check the LCD cable, disconnect it from the motherboard and then reconnect it. If the LCD screen still doesn't work, then the cable may be damaged.
# ***Reset the BIOS.*** The BIOS is the software that controls the basic functions of your computer. Sometimes, resetting the BIOS can fix problems with the LCD screen. To reset the BIOS, follow the instructions in your computer's manual.
# ***Update the BIOS.*** Lenovo often releases BIOS updates that fix problems with the LCD screen. To update the BIOS, go to the Lenovo website and download the latest BIOS update for your computer.
# ***Contact Lenovo support.*** If you have tried all of the above steps and you are still having problems, you may need to contact Lenovo support for help.