Press the menu button and move to the spanner icon, then select "Lock mirror up for cleaning".
Remove the lens, press OK and then OK again to start, follow the instructions on the screen....
When shutter-release is pressed, the mirror lifts and shutter opens.
To lower mirror, turn camera off.
Look into the camera body, the mirror should have raised and the shutter should be open, you will see a reflective green screen if the mirror has lifted and the shutter has opened, do not poke around, you are just looking.
If the mirror hasn't lifted no light will get to the sensor.
If the mirror lifted but you saw a black screen behind the mirror, the curtain failed to open.
Hopefully you will see the green screen. Put the lens back on to protect the camera from dust.
Set your camera to M, set the shutter speed to 5 seconds (that's 5" in the display) remove the lens and hold the camera as if taking a close picture of you computer monitor with a lit screen.
Press the shutter, you should get a 5 second exposure with no lens, this will only work in M, not A, P or S.
If the above checks of the mirror and shutter were working correctly, your "picture" should be all white.
This test eliminates any setting errors.
If the "picture" you took with no lens is black, with the mirror and shutter working, you have an internal electronic fault.