Project Lexus SC300 Road Racer: Part 10 – Finish Wiring the Back and Prep the Front Harness


Time to remove the aftermarket water temperature sensor.

At least in the short term, we are going to use the factory Toyota water temperature sensor. Project SC300 was equipped with aftermarket Defi gauges which are all being pulled. The water neck had been tapped with a 1/8 NPT hole for the Defi sensor, so this is going to be plugged.


Teflon tape on the plug helps to prevent leaks.

You can find 1/8 NPT plugs from a variety of vendors. Summit Racing has a warehouse here in Georgia and ships fast. Much of our -AN and miscellaneous common fittings were sourced there.

Note that teflon tape is not designed to fix mismatches in thread, pitch, or seat. Know when to use it and when it's the wrong tool for the job.


The hole was a little… yucky.

A tap is used to clean up the threads because they were not in the greatest of shape.


AEM sensors are also used for oil and fuel pressure.

The Haltech plug-and-play 2JZ harness came with provisions for both oil and fuel pressure sensors, but the plug locations were designed for factory sensors in factory-ish locations. Additionally, you really don’t want to attach sensors directly to things that vibrate a lot. That oil pressure sensor screwed into your block? Probably not a great idea.

So, in the “do things right” line of thinking, we are going to remote mount the oil and fuel pressure sensors and then extend the Haltech harness to reach.

AEM includes decent connectors and crimp pins with their kits, but we ordered upgraded connectors from MilSpecWiring for a few extra bucks.


First step- figure out where stuff goes. We looked at the existing Haltech connector to figure out which wire went into which hole.

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