2000 Bonneville oil pressure too high

Most likely the guage sender- but DEFINITELY have it tested. ASAP.

My first guess would be the sending unit but I would test it. It should work with a resistance to grnd. If it is shorting directly to grnd your gauge would read high. Check the dc voltage between pos 12 vdc from the battery & the ground leg going to the gauge. (Check on sending unit) If this reads approx 12 vdc the gauge should be reading correctly. Check with the engine off and wires disconnected also, if it reads 12 vdc the sending unit is bad. There are 2 legs on the sending unit as I recall. One should close an interlock relay allowing the fuel pump to come on after they system build

6 psi or so. This leg should show 12 vdc after required pressure builds. Make sure these 2 wires aren't shorted together. Also could have a blocked filter not allowing a good flow and causing a 100% grnd on the sending unit. If this is the case you should hear the lifters chattering. See if it takes a sec for the pressure gauge to drop after stopping the engine. Try changing the oil filter, & oil if dirty. This is my interpretation without having any prints on electrical system. Hopefully this will help.

Thanks - I'll check it out as you suggest. By blocked filter I assume you mean the main engine oil filter? I have recently changed oil (Castrol 5W30 synthetic) and filter so it should not be blocked. I do tend to hear the lifters chatter a bit at cold startup which bothers me

- but I believe this was true before the gage started acting up.

Thanks - I'll check it.