Nikon DX AF- S Nikkor 18-55 mm lens won't Auto focus

Make sure the auto-manual focus switch on your camera is set to auto (A) and also make sure the auto manual focus selector on the lens is in auto (A) as well. If your lens contacts are dirty then this will affect the function of the lens as well. Clean those with either a lint free type cloth and alcohol or methylated spirits.

if other auto-focus lenses work, then it is likely that this particular lens has a defect I suggest you send it in to Nikon for servicing

Hi,
Sorry to hear about your lens. If you are able to autofocus and take pictures with any other lens, then it means that your problem lies with the kit lens. If you can take picture in manual mode, but not in autofocus mode, then the AF motor in the lens in not functioning. I had the same thing happen to my 50mm 1.4 lens.
Depending on your location, there are Nikon repair centers in Melville, NY and Torrance, CA.
Hope this helps,
Andrew

without seeing pictures, I'd say you could TRY some plastic epoxy or some type of plastic-specific adhesive. i'm assuming you have the pieces that were broken off. otherwise, i'd say get a new lens...they are relatively reasonable used.

If you're looking at the camera without a lens on it, there should be a little flat protrusion in the lower left. Make sure that it is protruding and not obstructed.

problem in lens censer try to set the censer or replace it

Seems as if you're snapping the shutter before the lens has focused. Have you tried manual focus or single-server auto focus?

Try sending it to PhotoTech Repair Service in NYC. They are Nikon authorized, and can do the repair under warranty if you still have it. Also if you join they're facebook page, they will give you a 10% discount.
Here is the facebook page link, it has everything you need to send it in.
http://www.facebook.com/pages/New-York-NY/PhotoTech-Repair-Service-Inc/102527215194

Autofocus function on the D40 only supports lenses with the
AF-S feature, which have an autofocus motor built into the lens,
instead of using an autofocus motor drive built into the camera.

The Tamron lens you have, does not have a built in motor and
the autofocus function relies on the motor drive in the camera.

It will not work with the D40 or D60, but it will work with other
Nikon digital SLRs, such as the D80. Need to get an AF-S
type lens or upgrade to different Nikon digital SLR. Unless
you do this, you will have to manually focus the Tamron lens.

All of the Nikon DX (for digital) series lenses are also AF-S
type, so they will work with the D40, which is designed as
an entry level digital SLR, therefore it is intended primarily
for use with DX lenses, which are typically sold in a kit with
the D40. Most common one is Nikkor 18-55mm DX AF-S.

Other Nikon AF-S lenses made for film cameras (FX type)
will also work with the D40, but these tend to be expensive
professional models. DX series lenses tend to be more
affordable. You might consider the 18-200mm DX AF-S
as an alternative to the Tamron, but these are not cheap.

sir, replace ur lens image reading sensor