Nikon D3100 and Tamron 70-300 VC lens, pictures coming out underexposed on auto?

Just got the tamron lens today, but I noticed that all my pictures are coming out underexposed when the camera is on automatic. With the lens that the body came with (18-55) the pics are fine. Is there any way to correct this on the camera?

Return it and buy a Nikon 70-300mm lens.

So the Tamron lens was cheaper… Is it worth it if it doesn't work?

With the exposure button on the camera. Increase exposure to desired level. That's the beauty of dslr, there settings for almost everything! Actually not true, most P&S have this feature too.