Flashing yellow lights | DJI FORUM. Usually, flashing yellow lights mean you are in ATTI mode with no GPS signal. Were you trying an auto take off or manual take off? Auto takeoff will not work in ATTI mode
IMPORTANT info for new owners of Version 1.1.1 Phantoms!
Myself and at least one other V1.1.1 owner that I know of ran into the same problem when upgrading our new Phantoms to firmware version 4.0.
You must select D-BUS as receiver type or you'll get the yellow flashing LED indicating loss of Tx signal
depends on which Tx/Rx you have. Up until very recently at least the stock setting is PPM unless you have a 3rd party Tx/Rx then you might select D-Bus. But with the stock radio gear PPM is the default option"