Fuel Gauge Constantly Showing Full

[PoloCY60]

Please can anyone help with info or advice on the problem with my mother’s car, a 2010 Polo 1.4 CL Auto (no MFD) 60 reg?

I’m told that the fuel gauge has been showing full constantly for a few months. It’s done 40 miles since the last fill up and is still on full. The car doesn’t have an MFD so I just have the basic digital display fuel gauge representation to work with.

I’m visiting and only have basic tools (no VCDS, not even a DTC reader). Taking the car into a garage isn’t easy for my mother and I want to do what I can to save her money and hassle before taking that route.

The fuel pump unit connector has 5 pins:
1. Blue/White, which by the wire gauge I presume to be +12v for the fuel pump.
2. Blue/white, presumably for the level sensor(s)
3. Violet (ditto)
4. Brown/White (Ditto)
5. Brown, which by the thicker wire gauge I presume to be the earth for the fuel pump.

The resistances at the unit are as follows: pin 2 to pin 3 60 ohm, pin 3 to pin 4 340 ohm and pin 2 to pin 4 280 ohm, suggesting that pin 2 is between two resistances, one of 60 ohm to pin 3 and one of 280 ohm to pin 4.

Checking at the connector back along the loom, pin 4 went to earth and pins 2 and 3 were open circuit.

I didn’t check voltages at the connector as I was wary of generating error codes that might confuse later investigation.

These differences in resistance lead me to question the level sensors rather than a fault with the wiring, but I’m stuck with neither a maintenance manual nor a fault reader such as VCDS.

Any thoughts?