Bad Pcie x16 slot or bad GPU?

ANXsucks

Distinguished
Jun 20, 2016
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I recently bought a used GTX 460 and as I installed it into my PC, tho monitor couldn't detect the GPU. I'm only using a DVI to VGA adapter since my monitor only supports VGA but I am sure that the adapter is working. When the GPU is installed and I plug the monitor to the GPU, it only says "Check video cable" but when I plug it to the motherboard while the GPU is installed, it says "No input signal". But when I take off the GPU and install it to the motherboard, it's completely working. What seems to be the problem here?