thud on pressing power button

[samulam]

Hi, when I press the power button on my Auris, it is usually silent. However sometimes I hear a thud or a knock. Is this normal or should I have it checked.

If there is a possible fault what it might be.

[Gerg]

This post isn't a perfect match to your description of the situation, but I think you maybe having this happen:-

This may come about because you have released the handbrake *before* pressing on the foot brake pedal and selecting 'D' or 'R', so the car is then prevented from moving by the 'Park' (transmission) brake only, temporarily. 

When D or R is selected, the electrically operated transmission 'Park' brake releases almost instantly, and this will cause a noise as the engine/transmission springs back to its 'rest' position.

[samulam]

Hi, I always apply the foot brakes first, then release the hand brake( after selecting R or D.

What actually happens when one press the power button?

[Gerg]

Ah, in that case we may be talking at cross-purposes.  Likely someone else will have a better insight into this noise.

[TonyHSD]

Do you mean by pressing the power button you actually change the drive mode from an Eco or Normal to Power? If yes even while you are driving nothing should happen in the next 1-2 seconds after you press it than the car will accelerate rapidly and that thud (knock) you are worry about is the clutch in your transmission, it is dampen the excessive torque that has been created using all available power from both ICE and electric motors. This could also occur when ICE is working and you are coming to a complete stop after a harder acceleration for a very short time of period, for example you are accelerating from stand still and the car front of you stops unexpectedly and you are on the brakes. You can play with your car and if your case comes close to my description you have nothing to worry about. 
Regards