Pontiac Vibe trouble....Any mechanics please help!!!!?

[Josh]

Okay, so I was going to Walgreens the other day and my 2003 Pontiac Vibe wouldn't start back up. I turned the key to on and the dash lights came on. When I tried to start the car the dash lights went out....no clicking noise or nothing....the car wouldn't start. My first instinct was the battery cables....nope.....then I thought the starter.....took it off passed....then i thought the alternator.....nope passed too. Then I thought the battery....nope passed 100% which verifies the alternator was working. I was baffled. I then thought it was the ignition switch...I went to a few parts stores and none could sell it to me...they all said its a dealer part. So I had no choice, I had it towed to the dealer. They are telling me the power modulator or something like that is down. To fox it I would have to buy a new one for $475.00!!! I was so saddened to hear that. They say they hooked their diagnostics test up to it. It said error no codes are something like it. Anyways anyone have any idea of what it may be? I am so baffled and have no clue....I'd hate to pay that price and it not be it....Is the power modulator the brain? Please help me