I had the F06 error on my Bauknecht (Whirlpool) WA CARE 654 DI a few months ago and again just today. The difference was the behaviour when the error appeared.
A few months ago the drum did not turn at all. As it turned out one of the carbon brushes on the motor was stuck in its metalic housing due to fine carbon dust, which had filled up the gap between metalic housing and the carbon brush. After cleaning the brush and the housing the washing machine did its job again.
Today the drum turned and when the motor wanted to go to higher speed both the lights on "Spülen" (flushing) and "Spül Stopp" (flush stop) lightened. And this time the cause reason was the motor speed uptake on the motor- After removing the plastic cover of the motor speed uptake by pressing screw drivers into the space where the four cover holding clips are fixed and then pulling out the plastic cover it turned out that the ring magnet on the motor shaft was loose. I fixed it by putting a small strip of aluminium foil into the hole of the ring magnet and then pressing the magnet on to the holding pin on the motor shaft. After this the washing machine worked again.
By the way this brand/type is really bad quality. Other fixed problems on the same washing machine were the inability to start (due to a broken small plastic stick behind the start knob transferring the pressing force from the knob to a small switch on the electronic board) and the error signal "Wasserhahn zu" (water tap closed), despite the water is flowing, but maybe with too low pressure. In case of this error my wife is adding water through the detergent box (Waschmittelkasten) and pushes the start button, after which the program resumes from where it stopped before.