Fuel Level Sensing Flaky

[pbierre]

This is a 2013 XC70 T6, out West, virtually no rust, 114K miles. Over the past year, the fuel level sensing has gone flaky.
After filling the tank, it will show 1/2 full. But, a day later, it will show 3/4 full. During a drive, the display might start at 3/8 full, and then climb to 3/4 full.

I got my new iCarSoft Volvo/Saab V2.0 scanner, and it's seeing a

P134600 "Fuel Level Sensor B Circuit, General Failure. No sub type information"

Assuming this is a flaky electronic connection, can anyone detail the harness connections between the Fuel Sender,
Fuel Tank Module, and upstream path to ECM/CEM? thanks