Where does the little red wire go

I have a Banks OttoMind engine calibration Module. There is a 4 wire cable that runs from the module to the instrument panel. the 4 wires are Black, (common ground) Green (gauge) and White (gauge) and then there is a red wire, that has a small blade connector. The red wire is disconnected and there is no obvious place for it.

This system worked until about 4 months ago.

Yes I know it is an old system, but it worked?

We installed a new back up camera, and this wire must have been disconnected behind the instrument panel some how.

I checked for + power, not powered