Oil Pressure Gauge Issue

[jay71]

Recently had my 930 in for oil, tranny and break fluid change as well as alignment- and when I got the car home I noticed the oil pressure gauge pegs at 5 when the key is turned on. Goes back to zero when key is off, so the gauge isn't "stuck". I've read on other posts that this is what happens when there's a poor connection at the sending unit- or a bad ground at the gauge. Mechanic says the sending unit checks out okay- and he's unable to see any ground/connection issues at the gauge. Was hoping he's see where something was knocked loose at the last service- but all connections are there. The next step is to pay big bucks for the mechanic to spend a day chasing down the source if the issue which he seems to think lies between sender and the gauge. Before I go that route I'm hoping there's someone out there with some good ideas with regard to areas I should be checking to find the source of this electrical issue? Thanks, in advance, for your ideas.