3 flashes on this model is a heater related problem. What you can try frist is reset it just incase its a one off. To reset it press and hold the start button for several seconds and it will reset the electronics from there.
But if it does it again then you need to test the heater. This is located at the bottom of the dishwasher.
So remove the wooden plinth at the bottom of your kitchen.
Then remove the wooden outer door panel.
Then remove the metal cover at the bottom below the door.
Then on the right hand side under there you will see the heater attched to the front of the motor.
Remove the wiring block and test it with a multi meter. It should read about 28 Ohms. If faulty then it will need to be replaced.
If the heater is fine then remove the outer door panel and there you will see the wires running down the door. Open the plastic casing and give each wire a tug in there and check for any broken wires.
So try the above and see what you find but 3 flashes on this is a heater related fault. If you need anymore info just get back to me.