Modern vehicles are laced with wires. In the engine bay, there is no shortage of wire harnesses connecting multiple devices together. Making a replacement for a damaged harness, or in order to add a new device, might be necessary as the vehicle gets older. The components needed to make an engine harness are available at auto parts supply and home improvement stores.
Examine the vehicle/device wire schematic to determine the quantity and gauge of wires needed in the replacement harness.
Cut the wires contained in the harness to the proper length, per manufacturer's specifications.
Strip 1/4 inch of insulation from both ends of the individual wires comprising the harness. Twist the bare wires to eliminate strays.
Slide a harness crimp connector over each wire. Center the upper crimp section over the bare wire. The lower crimp section is placed approximately 1-2 millimeters under the bare wire on the insulation to serve as strain relief.
Crimp the two crimping points per wire, using the harness crimp tool.
Push each wire sequentially into the harness shells. Ensure that each wire at one end corresponds to to the other end. The wire is fully seated when the barbs on the connectors spring out inside the shell bodies.
Wrap the length of the harness in thermal heat barrier wrap. This prevents the wire insulation from potentially melting against a hot engine component, such as a header or vent pipe.
