Wiring Harnesses for Honda Civic ED

An engine management harness carries power, sensor signals and output drives between the ECU and the engine, and the reliability of the whole system rests on it. This section holds main harnesses, plug-and-play adapter harnesses and sub-harnesses, each listed for the ECU series it connects to.

Many faults on a standalone installation trace back to wiring rather than the ECU: a loose pin, a shared ground or a trigger wire run beside a coil lead. A purpose-made harness arrives with the right plugs, wire sizes and pinout, which removes much of that risk. It also follows a documented layout, so the next person to work on the car can trace it.

Start from the ECU, then choose the type of harness:

• ECU series: every harness is made for the ECU series in its title. Most are also built for one engine or car, so match both. Where a title names two units, the harness suits either.
• Universal wire-in: a plug at the ECU end and 2.5 m (8 ft) of flying leads, in basic or premium form. Every lead is routed, cut and terminated on the car.
• Plug-and-play adapter: fits between the factory engine loom and the ECU, so the car’s own sensors and plugs stay in place. Each is listed for the model named in the title.
• Terminated engine harness: a complete loom with the engine-side plugs fitted, usually for one engine family. Drive-by-wire-ready and cable-throttle versions differ, so read the title closely.
• Sub-harnesses and adaptors: coil-on-plug and high-output coil harnesses, injector sub-harnesses and breakouts, crank angle sensor, MAP sensor and drive-by-wire adaptors, an idle-valve harness and transmission harnesses.
• Auxiliary leads: flying-lead harnesses for direct plug-in units, adding inputs and outputs the factory loom lacks.

Lay the harness on the engine before fixing anything, and route it clear of exhaust heat, moving parts and sharp edges. Keep crank, cam and knock wiring apart from coil and injector feeds, crossing them at right angles where they must meet. Clip the loom at regular intervals and pass it through bulkheads in a grommet.

On a flying-lead harness, cut each lead to length and crimp it with the tool made for the terminal. Seal any splice with adhesive-lined heat-shrink. Fuse each supply at its source and run the main grounds exactly as the diagram shows. Before plugging in the ECU, check every pin with a meter against the pinout, and look for backed-out pins at each service.