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1G Rerouting the engine wiring harness

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Ok I figured this out while working on the wiring harness for my 1g turbo engine swap. There doesn't seem to be any information on this reroute at all, in the forums or articles, I am writing this tech article to describe it.

The 1g factory routing of the engine harness makes no sense whatsoever. All the wires enter the engine bay on the passenger side, behind the battery. The bulk of the harness goes along the firewall to the driver's side, wraps around the intake manifold, follows the fuel rail, and ends at the thermostat... Back on the passenger side. This is what the factory route looks like:
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There are several threads on here about wire tucks. Hiding the wire harness behind the fuel rail so that the engine bay looks cleaner. However, without rerouting the coolant sensor, o2 sensor, and cam shaft angle sensor (CAS) plugs, there will always be an unnecessary mess of wires wrapped around your intake manifold and fuel rail.

I did the reroute with the wire harness out of the car. It was very easy to do this way but it can also be done with the harness in the car. You would just need to unplug pretty much everything past the idle speed controller (ISC), remove the loom, reroute the wires, re-loom, and then plug everything back in.

Now for the actual reroute. With your harness exposed, trace the wires for the CAS all the way back to where the wires for the ISC branch away from the main harness. The CAS is located next to the ISC so this route makes way more sense then looping around the engine and back. Have the CAS wires follow the ISC wires and extend past the ISC plug by about 12 inches. You will need to shorten the wires.

The factory harness ends with the o2 sensor and the thermostat housing sensors (coolant temperature switch, coolant temperature gauge, and the A/C thermoswitch). This means that these are the longest wires in the harness. But why when the thermostat housing is on the passenger side of the engine, on the same side the wires enter the engine bay. This reroute allows you to remove a 2 foot chunk of the harness, removing with it a lot of unnecessary clutter above the intake manifold.

Trace the wires for the 02 sensor and thermostat sensors back to where the ISC branches off from the main harness. Instead of following the ISC route like the CAS wires though, the thermostat and o2 sensors will make there own route. This is what the ISC junction should look like now:
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From where the thermostat and o2 wires brake from the main harness, at the ISC junction, you will need about about 25 inches to comfortably reach their respective sensors. Cut the chunk out of the harness and reattach the wires to make it the desired length. As with any wiring, it is best to solder the wires back together and put heat shrink over the exposed wires.

After you have rerouted and shortened everything, rewrap the harness in wire loom. Keep in mind that not all wire looms are the same. There is standard polyethylene loom which is available at most home improvement and auto parts stores, this is what I used. There is also nylon wire loom which is automotive grade and is rated at higher temperatures, however it is more expensive and not as easily accessible. The nylon loom is identified by a grey stripe that runs along its length. Another option is to reuse your old, factory loom. Shop around before making a decision on your wire loom. Install the loom and tape the ends with high grade electrical tape to keep everything contained and protected.

Now the wire harness ends with the 4 injector plugs and the throttle position sensor (TPS). These are the only wires that will now travel along the fuel rail. This will give you a much cleaner engine bay and also make working on your injectors, fuel rail, intake manifold, etc easier with less clutter in your way.

This is all the stuff I removed from my harness. Keep in mind that I also removed 3 A/C related plugs (A/C sightglass, thermoswitch, and compressor plugs) and the BCS plug all the way back to the ECU connectors.
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This is what your harness should look like when you are done. I won't have an installed picture for the next few months but when I do I will add it here.
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I hope you found this tech article helpful. I think the reroute makes a lot more sense then trying to hide all the wires behind your fuel rail and should freshen up your engine bay. Who wants to see the mass of wire loom covering the intake manifold anyways. If you have any questions, pm me. Also if you like/dislike my idea leave a comment so I can know. I'd like to get some feedback on this. Thanks and enjoy your DSMs!

*** Thanks to Calan for the positive feedback and suggestions regarding the nylon wire loom.
 
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Since writing this tech article I have made a few more changes. First I rerouted the TPS plug so it follows the new CAS route. No more TPS circling around the Intake Manifold. However for the plug to work routed this way the actual TPS needs to be rotated 180 degrees. Now the injector plugs are the only ones on the intake manifold and I will run them under the fuel rail.

Also I removed the Solenoid Pack plug. This is the plug that connects to the fuel pressure solenoid and the purge control solenoid valve. I will be deleting both of the solenoids.

All and all I am very pleased with how my harness has turned out, can't wait to see it under the hood!
 
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