we are getting no oil presure on the instrument panel gauge when the engine is running low RP When the RPM's are up, the oil pressure reads normal. How do I test to see what is wrong? There are 180k miles on this vehicle. It is unknown if the engine has been rebuilt.

 

I think I might be having the same issue (2001). Except my gauge shows no pressure when it's cold during the first start up in the day. After it warms up a bit it's fine for the rest of the day. Curious....