Fuse has blown for the yellow wire. The voltage should be the same as the red wire.
The 2.3V is just a ghost voltage, no power actually there, it's just the very high impedance of a digital meter means it 'senses' some voltage that is being induced in to the wire as it runs through the harness with other wires that are carrying power.
Check fuse F17 and F18 in the engine bay fusebox.