ECU light

[Numplumb]

I bought my donor parts already removed not a donor car, and it seems that I don't have a warning light for engine fault warning so I have 2 questions

1) does anyone know if I could add a wire to the ECU to fit one, the circuit diagrams I have show the wire as being black/yellow there isn't a wire of that colour in my ecu connectors I do have quite a few empty spaces though.

2) If it is possible does anyone know which connector and position to connect it to.
Regards Mick.