Last Updated
23 June, 2005

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Installing the 3SGTE

Wiring the TEC³ and Sensors

  WARNING: While I preface all of these guides with a disclaimer, I think it's important to bring it up again.

I'm not sure these instructions will work for your car. I'm posting them in the hope they help somebody in their project. They are not gospel, they might even contain errors. Nobody's perfect. You are on your own.

So if you follow these procedures and burn up your ECU, your wiring harness, or otherwise damage your car, I'm sorry, but I am not responsible. Be careful, and get input from many sources. If you are not sure what you are doing, and you can't afford to make a mistake, take your car to a reputable speed shop.
Troy Truglio assembled the components for my TEC³ package, and it included the "Power Harness" as well as the standard harnesses:
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The TEC³ harnesses are terminated at the ECU end. While the sensors include nice GM-style automotive connectors, all of the other leads need to be spliced into either the stock sensor leads or other aftermarket connectors. I also decided to add an idle air controller valve (IACV) and a cam sensor for full-sequential fuel injection.

When it comes to splicing wires, there are opposing camps on which connection type is best. Crimped butt connectors can produce excellent joints if the the crimp is properly executed. Seamless connectors are recommended to prevent a "flattened" joint, which is usually suspect. Connectors are available for many types of finished joint, from simple un-insulated tinned copper to elaborate crimp-and-solder connectors with adhesive lined heat-shrink insulation. The latter are targeted for marine use, and cost roughly 10 times the cost of a simple butt connector.

Since automobile manufacturers universally use crimped connectors, it's a pretty good sign that a properly made crimp connection is a solution of choice. (Please don't start a flame war on that statement!)

For most of the splices, I used uninsulated seamless crimp connectors from 3M, with polyolefin heat-shrink tubing for insulation. I also used a ratcheting-type crimp tool to get consistent results.
Figuring out where each circuit lead should go is a daunting task for the first-timer. I consulted several sources.

The Electromotive TEC³ manual is an excellent source, as the circuits are described in detail. The BGB provides information about the circuitry on the 3S-GTE, and the BGB Electrical Wiring Diagram addendum has the circuits all laid out in color. An excellent guide. And Ricky Benitez has an excellent write-up on installing a TEC³ in an MR2.

Unfortunately, none of these resources covered everything, as they all had a slightly different focus, just as this guide won't work for a different configuration. However, the combination of all of the resources made me comfortable in proceeding.

It's really a matter of being careful and organized as you proceed. Trying to get this done in a hurry is asking for trouble. You need to check and double check everything. And ask questions when you aren't sure. I asked plenty of questions of Troy, Ricky, and Electromotive Tech Support.
My first step was to list all of the TEC³ leads in a spreadsheet, and then track down their purpose one by one. I then labeled every wire in multiple places to make it easier to identify them once they were in the car. Trying to tell if a wire is red with a blue stripe vs. red with a black stripe is difficult under poor lighting conditions, and I wanted to remove as much uncertainty as I could.
I had hoped to eliminate the OEM engine wiring harness entirely, but that proved close to impossible. Toyota's likely goal in fabricating the harness was low production costs, not making it easy to identify, isolate and/or eliminate individual circuits. I ended up with a much simpler factory harness, reducing the connector count from 36 to 8:
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It's still a bit tangled, but that can't really be avoided unless you want to re-splice the factory connectors to eliminate the intertwined wires. Without the proper tools, that's risky, as you could end up with a non-working harness. Besides, eventually this mess will be hidden inside black plastic sheathing.

As I disassembled the OEM harness, I took photos of the OEM connectors, along with their associated wires.
  Essentially, I needed to create a new engine wiring harness from scratch. While it is certainly possible to install an aftermarket EMS utilizing existing wiring, the scope of my project seemed to suggest a fresh start would be cleaner.

I'd also added some components that weren't strictly necessary, so the job had become more complex in the process.

My plan was to install run the wires to their locations, get the car running, then try to clean up the mess. It would be much simpler to troubleshoot any electrical problems when the wiring was exposed than to trace it down after everything had been buttoned up. While I took some steps to neaten things up, they were simply to safeguard the wiring, and were reversible.
  Since the TEC³ is the largest component, the first step was to mount it, then find a spot for everything else. Here's the initial location:
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The biggest constraint was the location of the bulkhead holes for the wiring harnesses.
  I attached the two main TEC³ harnesses and ran the wires through the bulkhead. I then attached the TEC³ Power Harness to the bulkhead, to the right of the main unit:
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The starter relay was relocated to a new location.
  I had an auxiliary fuse box from a previous project, and I was going to use that for a number of tasks. I installed that to the left of the TEC³:
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  The MSD tach amplifier needed a home, so I placed it between the fuse box and the ECU:
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  I also had a couple of fan controllers for the purpose of managing the intercooler and engine lid fans:
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The controllers will will cycle the fans on and off depending upon the air temperature readings from a couple of temp sensors.
  As I dug into this part of the job, I realized that photo-documenting every step was going to be time consuming and, frankly, not much help for others. Running wires isn't unique to this project, and it's likely that you'll find your own way to do this. I will note the terminations as I complete them, and mention any problems I encountered along the way.
  Previously, I had put together a spreadsheet showing which TEC³ wires were going to be needed, and where they needed to go. Ricky Benitez's How-To was a great help, as was the TEC³ Installation Guide.

First, I had to determine the general target location of the wires -- which ones went through to the cabin, which ones went to the right side of the engine bay, which ones to the left. This also showed me which wires needed to go through which bulkheads.

I found that the hole through the forward bulkhead (into the cabin) was not really adequate, so I enlarged a smaller thru-hole located there, previously used for the engine lid latch release cable. I opened it up to 1½" in diameter with a hole saw and installed a rubber grommet of that size to protect the wiring.
  I ran a 10AWG ground wire from the battery to the rear trunk to provide a solid grounding point for all of the electronic components. I didn't want to be chasing grounding gremlins along with all the other unknowns in this project.
  Some of the wires needed to be extended beyond their original length -- mostly the ones going to the left of the engine bay. The cam sensor wire, for some reason, was quite a bit shorter than the others, and of course instead of being a simple set of standard hook-up wires, these were twisted and shielded inside a foil wrap, all of this inside a black sheathing. Kind of like a microphone cable. This wire was about 4 feet too short, so I'd need to locate something similar to extend it with.
  I ran the wires out from the trunk, and immediately the scope of the problem started to dawn on me:
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I could see that my original plan to install most of the engine components before running the wires was now going to slow me down as I tried to find a clean way to route all of these wires to their targets. On the positive side, the engine bay was still much more accessible than the one in a stock MR2 Turbo.
  I had not yet installed the crank and cam triggers, so that was next.

The crank sensor is secured into its bracket with a single set screw. I replaced the stock screw with locking screw that hopefully wouldn't back out later:

I noticed that the sensor wasn't exactly perpendicular to the trigger wheel centerline. Since the air gap between the two is pretty critical, that needed to be corrected.

I tried rotating the sensor bracket with the mounting bolts loosened, but it didn't really have much play in it. So I removed the mounting bracket and disassembled it. By elongating one of the holes, I was able to rotate the sensor mount on the base plate enough to achieve perfect alignment:
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Now the sensor can be adjusted for air gap.
  Routing the trigger sensor's cable past the various moving parts in the immediate area was a priority. I used a couple cable ties to secure it to its bracket...
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...I snaked the cable up under the alternator bracket's lower mount...
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...then ran it through a lined cable clamp I'd installed on the intake manifold:
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The crank sensor had a long cable with a WeatherPack connector on the end that would reach into the trunk.
  I mounted the cam trigger assembly approximately in the correct alignment on the left engine mount:
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This, too, would require exact alignment later.
  I needed to run a few wires from the engine compartment fuse box into the trunk. One of these was spliced into the OEM ignition relay circuit to energize a switched (ignition on) +12V circuit.

I detached the fuse box from it's mounting brackets and flipped it over. The wire I was targeting was the Black w/Orange wire leading from the ignition switch to the Ignition Relay:
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The yellow spliced wire can now be used for a number of circuits that need a switched +12V signal, but only for low-amp circuits.
  The downsized OEM engine harness still has a couple connectors that install into the fuse box:
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  A few high-amperage circuits that provide battery power need to be wired into the fuse box as well. These include some wires from the TEC³ Power Harness and the auxiliary fuse box. These are connected to the studs with ring connectors. The auxiliary fuse box also includes an in-line circuit breaker that fits nicely inside the box once its mounting tabs are broken off:
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  With the additions to the fuse box circuitry completed, the wires are bundled up and taped to the S-shaped conduit that attaches to the side of the box. The bottom is reattached, and the fuse box is mounted back in place.
  I started sorting out the wires into groups. I snaked a bunch of them under the air intake and through the bulkhead into the cabin:
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  The next batch was headed to the left side of the engine compartment. I wrapped these in a length of cable sheathing and ran it under the intake manifold, securing it with lined cable clamps attached to pre-existing 6mm mounting points in the manifold:
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Continued on next page...


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