hi I have a 51 plate Voyager with a fault code p15 11 can any one give me a clue as I have been told it could be the ecu

 

I take it this is a Diesel? that code it battery sense code. first check is fuses I have seen the fuel heater fuse can blow and set this code. It will also make the lights pulse at idle as the ECU does not know the battery voltage so doesn't know what charge rate to set the alternator at so is turning it on and off. I have also see broken wire from the fuse back to the ECU (sorts on on ECU bracket, under battery tray or on the plug under the fuse box) but never fitted an ECU for this code but yes could be but not likely.