The Car:
Mercedes 2006 A Class A160 CDi 2.0 diesel (W169 model).
The Problem
ESP light came on simultaneously fuel gauge stopped working and speedo not working.
Suspect electrical fault. Scanning revealed o/s front wheel speed sensor fault. As we couldnt understand why this would be connected to the fuel gauge we initially assumed electrical or ecu fault. Further investigation did not reveal any faults and so we ordered a new sensor from the Mercedes Dealer part number A169 540 17 at a cost of £72.36.
The Solution
After fitting the sensor which took approx 20 mins all faults cleared.
Conclusion was that for some reason in this car the fuel gauge is linked to the abs wheel speed sensor.
Problem Solved.