2,4 is a memory error according to the service manual.  Power off, disconnect the battery from the system board and hold the power button for 30 sec.  Remove and reinstall both memory modules and see if the system will then power up. If it still won't, try one module at a time in each socket until you isolate the bad module (will fail in both sockets) or the bad socket (both modules fail in just one of the sockets).  Then replace the bad module or the system board. Service manual here: [URL]  
The m15 R6 turns on, ventilates, the led stays on but the screen does not turn on. The button led is in sequence: 2 times red and 4 times blue. What do I do?
m15 R6, turns on but the screen is black