Just put a pin or something on the ecu side of the harness that grounds...grab a volt meter, and then hook the ground wires up accordingly so you get a ground signal when you touch the pin on the ecu side of the harness, I think the plug was blue.

 

Almost done with my harness but one issue.

Automatic and manual thermostat housings are different there is an automatic transmission temp sensor ( brown/single wire).

I need someone to confirm. Thermostat housing connectors needed for a manual fd?