2013 Mustang GT Fuel Guage Intermittent Fault W/ B1A75:15

The vehicle is a 2013 Mustang GT (5.0) with roughly 150K miles. It had a check engine light and the fuel guage read empty.

P0463 Fuel Level Se Sensor A Circuit High was set in the PCM.

B1A75:15 Fuel Sender No 1: Circuit Short to Battery or Open was set in the IPC.

The No.1 sending unit was 11-12 ohms (within specs 10-180 ohms).

I found the following circuit measurements:

No.1 Input to Chassis Gnd = 5.5 AC
No.1 Return To Chassis Gnd = 0.0 AC
No.1 Input to No.1 Return = 5.5 AC
(No.1 Input to No.1 Return = +5.5 DC)

No.2 Inp to Gnd = 5.5 AC
No.2 Rtn to Gnd = 5.5 AC
No.2 Inp to Rtn = 11.0 AC
50 Hz

When I rechecked the circuits this morning, the fault was no longer present. All circuits to chassis ground had 5.5 volts AC. Both sending unit PID levels were roughly 330. Cleared DTCs and performed the IPC self test (passed). The fuel guage showed 3/4 tank. Road tested the vehicle. No.1 peaked with side to side swash. No.2 peaked with fwd to aft swash.

I think the cluster was at fault due to the 5.5 AC (+5.5 DC) measured between the Inp and Rtn circuits. There was potential to ground on the circuit, but the module flagged an open/short to voltage code not the short to ground code.

I'm not familiar enough with the Mustangs to be certain though. Honestly, I was surprised to find AC voltage present. Is this done for monitoring fuel swash? Does phase shift indicate swash direction? Can anyone explain more or point me in the right direction for answers?

(Is this cluster just a unicorn and putting out AC voltage into the fuel tank? :huh: )

@4 minutes, 44 seconds

This screen capture from the video shows 500 millisecond of time and 25 square waves, so that means there's a 50Hz constant signal coming from the instrument cluster to the sending unit. I cannot find in service info that this is a normal condition, I can only assume this is normal because you mention 50Hz and this YouTube video also shows 50Hz.

As for the two codes you were getting, this identifix test from Terry is a good way to narrow down if it's the circuit or the cluster: