If you do not have any RB20, RB25, or RB26 you well have to buy another harness... Greddy makes harnesses for a BUNCH of cars & they make a universal harness also. The harness Plugs up to your ECU and Main harness that goes to the ECU. If you do not have a RB series motor your going to have to buy another harness... thats why I'm selling them separate.