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What code is prolink reading,, the numbers please?
You have two fuses that supply your ecm power they will either be in battery box,,next to ecm,,or by starter,,
The ecm needs constant battery voltage even with key off,,it also gets power from ignition switch to wake up ecm when key is turned on.
Eng SNS stands for sensor supply volts low,,all your engine sensors should have a 5v wire going to them from ecm,,that code is saying its low,,so the first thing you need to do is check voltage at fuses with key on and engine running,,should be the same as battery voltage.
You need to start with cleaning all battery cables and connections ,,find fuses and inspect for any corrosion,,repair any that are poor connections.
FL also has issues with pass through connections on engine firewall so make sure to check those,,also any ground post on firewall are common issues along with corrosion in fuse boxes.
Check ,,inspect, and repair all connections.
This is a self clearing code that will go away once problem is fixed,,it will also keep fan on!