Manifold pressure gauge not working

[flattop peet]

Hi, I have a 2006 379, C-15 Acert. It's new to me, and I'm trying to work all the bugs out. The manifold pressure guage does not work at all. Zero movment at all times. I'm Assuming it would be the sensor which I priced out at Pete. (must be made out of gold and silver ) Before I dump $300 on a new one I'm wondering if someone knows how to properly test the old one to help me isolate the problem. Thanks in advance.