How do I diagnose and fix my new world dishwasher?

My new world dishwasher is coming on and appears to run through the programme, however after the first small water intake on pre-wash it doesn't take in any more water.
It seems to run through the whole programme even though it hasn't taken in any more water but is cold when it ends.
At the end it shows two flashing lights (rinse and dry) which according to the troubleshooter means LONGER HEATING TIME BUT NOT REACHING THE REQUIRED TEMPERATURE. With the possible cause being a malfunction of temperature sensor or of heating element.
Would this stop the machine taking in water?
How do I identify the temperature sensor?
I can identify the heating element but don't know how to figure out which part is faulty, the element or temp sensor.
And finally can I replace/repair this myself?, I have in the past replaced a cooker element fairly easily and if this is along similair lines, I'm sure I could manage.