Vehicle operates normally even when eFlexFuel control unit is not on. You should use only gasoline if the control unit is not on. If the ethanol sensor is installed to breather hose, then the ethanol content is 0%.
How to repair
Check wiring harness and all the connectors. Especially ground wire and red double wire
Check that the ground wire is connected to ground place
Check that the ethanol sensor is connected to the fuel line