Sigma mystery wire

[ChrisC]

I was fitting a shift light this weekend, and came across a it of a mystery in my 2011 ex Academy cars wiring. I have an wiring diagram for the car that shows three connectors between the engine loom and the chassis loom, the smallest being the connector I was going to extend for the Tacho feed for the shift light. But this is where I have a mystery wire, the diagram shows two wires, but I have three. A brown yellow to the alternator, to show battery charging (on the diagram), the white black ecu to Tacho (on diagram) and another white brown ecu to Tacho, but what's that for.

 

The diagram shows one white brown wire but this is for the oil pressure switch, which is not an eyelet as described, but three completely different colour wires going to a danfoss switch.

 

It connected to a programmable I/O on the ecu according to the SBD site, anyone got a clue to its purpose.