Just an FYI for reference . . .
I had the ECON light failure on my A6 with no aircon, VAG-COM showed G65 sesor not reading (short/open circuit) and a pressure test showed plenty system pressure . . .
On this car the G65 is on the RHS of the condenser, underneath the RHS headlight and behind the bumper, I had thought headlamp or bumper removal may be needed to change it, but managed it through the foglamp aperture (pull off the trim on the bumper), very tight but possible, took about 15 mins to change.
The G65 itself had failed through corrosion, the aluminium casing had ruptured and allowed moisture to destroy the electronics inside.
You CAN change the G65 without depressurising the system as there is a self sealing valve on the condenser . . . which is nice.