EDC Auto ,Check engine Light

The check engine light keeps coming on, on my 300tdi auto. When ever i come to a stop the engine does not tick over the check engine light comes on and the revs increase to roughly 1800 rpm.
If i very gently touch the accelerator peddle the light goes out and the revs go back down and she will tick over, any ideas pleae .

Stick it on Testbook to read the codes,but I would expect a failed crank sensor,because of the high idle speed.The Engine ecu defaults to the needle lift sensor when the crank sensor fails,but its not such a reliable signal and disappears on overrun.