D3100 not auto-focusing

Hello,

I have bought a D3100 with the standard 18-55 mm lens about 2 years ago. From one day to the other, the auto-focusing stopped working all together and does not allow me to even take the picture. Only when I switch the selector to M for the manual focus I am able to take a picture.

I have swapped the lens with a friend who has the same camera and it does works therefore it is not the camera.

The lens does not appear to have any physical damage nor it has fallen, is there a reason why all of a sudden it has stopped working?

Thank you for your help!

The focus motor is in the lens so if another lens works, it may be your lens or, hopefully, it's just that you need to clean your lens contacts? Other, more experienced people will chime in.

A little unclear, Does this lens work on another camera, or does another lens work on your camera? If you can, try it both ways, it may indicate whether its the lens or camera.

Clean the lens contacts with a pencil eraser. Then brush off and wipe clean.

Move the switch on the lens to auto.

There is really nothing to clean off from the contacts...I did anyway but it did not change anything.
Seems to be an issue with the AF motor, strange thing is that it stopped working from one day to the other...after 2 years, is there any hope for warranty??

thank you all

The lens should have a 5 year warranty

Thanks, where do I go to claim the warranty?