2008 gmc sierra oil pressure drop.

You could replace the sending unit as a test or install a mechanical gauge which would be immune to RF interference. I would check your oil level if you have not.

I just experienced the same thing on my 2008 Sierra 1500. It would go to approx. 35- 40 psi then within one minute it drops to zero and alarm and oil light comes on. No strange engine noises. I bought new sensor and 1 1/16" deep socket and about 4-5" extension and swivel socket. I saw on YouTube that there are two ways to go about this. One, remove intake manifold which is time consuming, or remove vacuum hose to brake booster and other end which comes in through the rear of the plastic shield. Very hard to get any tool on hose clamp at engine end of hose. Remove fuel line retainer clip that secures line then use a line release tool to remove line. Pull EGR hose out of valve cover I believe, then you can get the wire plug disconnected from sensor. It has a release tab on the firewall side of plug at the bottom of plug. Lift up and pull plug off. Put the socket with swivel and extension on sensor then ratchet. Remove then use a curved metal pick to go inside hole of sensor and carefully remove mesh screen. This was where my issue was. The screen gets clogged and sends bad sensor code. Just use brake cleaner or B12 and clean really good. Replace screen back in the hole. Remove yellow rubber washer from old sensor and put in new sensor the same way it was in the old one. Put sensor in and tighten. Don't forget to reinstall plug to sensor and just go in reverse for replacing all lines and hoses. Now I forgot the screen step and had to go through this all again. However, I thought I might try and remove the sensor without removing lines and hoses. With smaller hands this is possible. I was able to do it. My screen was dirty and clogged. After cleaning and reinstalling, light went off and pressure remains at 40-50. Sensor cost me 54.00