2005 Chevy silverado oil pressure guage is on zero , oil level is fine, changed sending unit with no result,

Put a gage in the sending unit hole and see if the oil pump is weak, that is the best way to tell if the engine pump is ok.

It could be the sending unit. If the truck is low on oil it will cause something similar. Be sure the oil level is topped up. The only way to be sure it so measure the actual oil pressure at the engine with a proper gauge..

Do you hear lifters ticking? Or knocking inside the engine? Do these sounds change with engine RPM? If you don't hear them it is likely a sending unit, if you do then it could be the oil pump. Either way, you need to hook a mechanical oil pressure guage to the engine to confirm which is the problem. If the guage shows normal pressure then the problem is the sending unit. If it doesn't then you need to look further and this would best be left to a professional.
I would be very reluctant to drive this until you confirm which one is the problem because if it is indeed the oil pump even a short drive can ruin the engine. Hope this helps.

You probably need a oil pressure sending unit it is located at the back of the engine and is a high failure

the oil sending unit is bad

the oil sending unit could be out or the pressure guage is malfunctioning is the service engine light on?

the oil pressure sender unit tip is got sut build up remove it, clean or replace it. when oil is thin it gets right in but while its cold and thick it wont trigger the sending unit. causing light to come on.

your oil sending unit in the block is bad

Hi, this is a pretty common problem on these Silverado instrument clusters. We can repair it for you or provide you with the parts to do it yourself. Click here to learn more about these silverado instrument cluster problems:
Dr Speedometer Instrument Cluster Repair Speedometer Repair Guage...

Check the wire behind the guage.If not tight it will make the hand bounce.