Help needed confused

[grantym]

So I'm having a bit of a headscratcher. On diagram y194 is a fuel pressure regulator.. On the bench 1 wire is 12v and the other is ground - negative.
Once plugged in there's 12v on one side of the plug wire and 5v to 10v on the other wire should that not run on a negative earth can some1 see on diagram what's is voltage or if there's meant to be a negative side of the item

 

[grantym]

So I'm having a bit of a headscratcher. On diagram y194 is a fuel pressure regulator.. On the bench 1 wire is 12v and the other is ground - negative.
Once plugged in there's 12v on one side of the plug wire and 5v to 10v on the other wire should that not run on a negative earth can some1 see on diagram what's is voltage or if there's meant to be a negative side of the item

 

[brianmoooore]

If Y194 is an analogue sensor, I would expect to see a voltage on pin 1 of less than 12V, with the actual voltage being dependant on the fuel pressure. Between +5V and +10V is a reasonable range to expect.