Oil psi 0 below 20 mph or at idle

Yesterday my oil PSI started to go down to 0 at idle. If I manage to get to highway speeds it'll start showing pressure on the gauge.

I have a new pressure sensor on it. What could be causing this?

 

Could it be anything else as well? Hopefully its just the water pump if its not the sensor or bad connection.

 

Its a 60 series detroit, DDEC IV.

 

Mechanical gauge said 0 pressure. Leaves out gauge and sensor.

Looking at the sump is the next step, but not something I can just do in a parking lot covered in ice.

 

At this point once this is done I'm just pulling the motor out for rebuild.

With stuff like this going out earlier than they should, it'd be easier to bite the bullet.