1. If the light is on continuously with pressure in the fuel system, but goes out when depressurised its almost certainly a blocked filter.
2. If it is on continuously even with the engine stopped and no fuel pressure, its an indication fault.
2.If it then goes out when the connector is disconnected from the switch, its a switch fault. What you do next is between you, the LAE and the DDG.
3. If it stays on when the connector is disconnected you're looking at a wiring fault - most likely a short within the connector. The fix depends on having the right tools.
This post is probably just about as useful as the average FIM ever gets but as usual - what you really need is a good LAE. Preferably a proper 10.1.6...
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Through difficulties to the cinema