Engine Harness Colors and meaning
 

I'm working on integrating my factor 2001 Harness pig tails to a Fuel Tech FT450. I can't find any place where it tell me what wire does what. This weekend I will fill in the empty wire colors.


https://cimg3.ibsrv.net/gimg/www.mia...570728f52e.png

Wiring diagram for '01 is pretty easy to find.
https://www.mellens.net/mazda/mazda_...001_wiring.pdf

Cam Sensor:
Black/Blue: Ground
Gray/Blue : Sensor Signal (Pin 3V of ECU)
W/R : 12v

Injectors
White/Blue - 12v
Other Colors - Signal from ECU

Air Temp
Piink/Blue - 4N of ECU Connector
Black/Red = Sensor Ground 4O of ECU connector

The rest should be pretty easy to identify. Most should be in one of the three "Engine Performance Circuits" pages.

Same wiring Harness diagram I have downloaded before, but it doesn't show which wire is for the 5 Volt sensor system. I'm wondering if the Blk/Red is the 5 Volt from the ECU. Sometimes there is 12 Volt and command wires going to the same component, which the diagram doesn't decipher.
https://cimg3.ibsrv.net/gimg/www.mia...13755b5fbd.jpg



This is the Wire system for the Fuel Tech 450, it's pretty simple then looking at the 3 pages for the Miata Engine Harness
https://cimg3.ibsrv.net/gimg/www.mia...6e62ffa1ed.jpg

There is also 3 connectors on the front of the Engine. The First 1 on the Left is for the Injectors, but there are 3 wires that don't make sense for what they would correlate with the wiring diagram mentioned above. What is the Center connector for, ground maybe. I don't see it in the Diagram.
https://cimg3.ibsrv.net/gimg/www.mia...767e31f9a7.jpg
Here is 1st of the 3, all 8 wires
https://cimg7.ibsrv.net/gimg/www.mia...9913c8a3c4.jpg
Then the 3 left over wire?
https://cimg8.ibsrv.net/gimg/www.mia...157292bc8a.jpg
The second connector has 4 wires, all mosty black
#1 Blk
#2 Blk/Wht
#3 Blk
#4 Blk/Wht

Trace the wire all the way back to the PCM in the diagram

You see how for all the blk/red (for IAT, CLT Temp, TPS, etc) goes back to pin 4O of the ecu connector?
Take that information and then look at the ecu pinout
https://www.miataturbo.net/attachmen...cu_pinouts.pdf

Reviewing the ECU Pinout PDF, we see that 4O = Sensor ground.
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Note, most tempature sensors are only 2 pins which are "Signal Ground" and "Sensor Output". There is no 5v which is why you see the IAT sensor only have 2 plugs and none of them being 5v.

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If you want to see which wire is 5v, it is 4L on the ECU connector (confirm this on the ECU Pinout PDF).
This would be the Light Green/Red wire you see on the TPS.
https://cimg0.ibsrv.net/gimg/www.mia...ad8cf15135.png

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In my opinion, your best bet is to NOT touch any wires in the engine bay. Buy/build a jumper harness like this (facebook[.]com/groups/MiataDIY/permalink/3521791234814711/) and then wire your fueltech directly to the ecu connector.

Thanks for the help I'm going to dig into it more tomorrow. The factory harness is destroyed after being out in the weather so I'm working off pig tails. I really dred doing wiring. I'm going to solder the wires then heat shrink the joint along with the whole harness getting a antichafe heat shrink treatment.
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