04 Silverado 2500HD need to reset oil pres gauge. Help!
 

As stated I have an '04 silverado. 6.0 Gas. I recently had some electrical issues and while trying to track down battery drain I had the battery unhooked for a full day.
Now the oil pressure gauge goes up every time I start the truck but when I shut it off it doesnt go back down. After a few starts the needle is wrapped clear around and almost pointing straight down.
the truck runs fine but I need to somehow reset this gauge.

Any ideas?

thanks

MArk