porschelou

Hello,
I'm working on a friends 06 Miata. The car has a new LS-3 installed and is ready for wiring. I have a new GM stripped out harness that is ready for install. Can you direct me to any good write-ups for this harness? Also, trying to find the schematic. I have searched / looked around this site and didn't see much for this config.

Also, curious if anyone has broken the CAN Bus code to interface with the OEM gauges. Might end up with a set from Speedhut.com.

Thanks
Great Site -
Can't wait to get the beast running...

charchri4

I spent 6 miserable years as an electrical systems specialist at a large Chevy dealer and compared to a lot of stuff I have run across wiring one of these is a piece of cake. But I'm not following what harness you have with the new GM harness. Is that a stand alone that came with the engine or something? Where did you get it?

porschelou

Sorry - I should have put more detail in the message..

The wiring harness is new from GM #92238351 - the owner had a local chevy tuner shop remove all of the un-needed wires

The ECU is new from GM # 12633238 - The tuner shop will put the code / dyno the car once running

Looking for the wiring schemtic to help with the install. I have the full set of Mazda manuals.

Thanks

Gator Bait

So the shop trimmed down the GM harness to just the required wires but did not label them? The part number reflects a 2010-2012 Camaro harness. I would start buy searching for those schematics or repair manual.

charchri4

That's what I was wondering too. No labels?

It's really quite straight forward. The injector and coil harnesses will only go one way on the engine and the rest of the plugs for the throttle and sensors should lay out in about the right place and be obvious. You will need the ECM pin outs to find the tach and VSS for the dash and where to apply power and ground. Are you going to use the drive by wire? Dumbest thing any engineer ever dreamed up by the way but a good money maker for shops...

porschelou

About half of the connectors are labelled - I can figure out where the others land. I'm stepping in to this project after the owner had already bought everything and had the shop remove the "extra" wires.
The questions I have:
- Where the heck is the ODB II connector (It's not on this harness)
- There is one relay ( I'm assuming this is the fan relay - one speed?)
- There are a few wires I need to figure out:
- Heavier gauge purple (fan?)
- Pink
- Red
Where do most folks grab the 12V+ hot / switched power from? Yes we will be using fly-by-wire.

I want to hide as much of the harness as possible - so I will probably end up lengthening the harness at points. I also don't like the miata fuse box sitting in the engine compartment - has anyone ever mounted it under the dash and then run required wires from there? Really want to end up with a sterile engine compartment.

Brown&Miller is making all of the fluid / AC lines. They do many of the cars for Nascar - benefit of living near Concord NC

Thanks for your help.. I'll try to get some pic's up this weekend.

charchri4

OBD will be easy to figure out when you have the computer pin outs. The plug under the dash will have the hot and ground etc in it so you just take the wire that went to the Mazda computer and run it to the GM one.

The relay could be the fans or the fuel pump or some sort of a main power relay. I don't know the NC at all but most set ups have 2 fans and 2 fan circuits from the computer to run them. So that would mean 2 relays and kind of rules out the fan. Check if the computer pin outs have a high and low fan out put. It could be anywhere from 1 to 3 relays running them depending on how the computer and harness is set up.

For the unknown wires where do they go? Do they start in the fuse block, computer or? No heavy wires should be going to the computer and there are only a couple of things that are run by heavy wires in the car. My guess is they are some sort of main feed to a fuse block because everything else is lighter wire.

For power that's a bit of a wild card because there are a number of options. If it is a stand alone harness with it's own fuse block you only need a constant and keyed power source. Probably the most common is to use the power that powered the Mazda computer to run the GM one. Really Mazda has the infrastructure for what you need in the car. The fan wiring is there from Mazda you just need to wire the GM computer to turn their relays on. Ditto with the fuel pump and AC.

It's really hard coming in to the middle like that and you may have to go wire by wire on this one. Start at the computer and you should have about 125 wires. Just go wire by wire through the computer pin out and make sure every wire goes where it should. It sounds daunting but it really is not becuase nearly all of them will go into the engine harness and are easy to follow.

porschelou

Thanks for the replies. Got it figured out. The ODB harness was separate and the owner had it on his desk. Everything is clear now.. but..

I don't want to mount the ECU under the hood ( going for a clean engine bay) so I'm going to get a custom harness made to relo the ECU to the trunk. Any suggestions of who a good harness builder is? Space is going to be very tight under the dash so I can't really move it there. Moving the OEM's huge underhood fuse box in the glove box area ( and keeping the heater box)..

Let me tell you - removing the dash was lots of fun.. My hands will be healing for a while

Going to start removing all of the ABS / Airbag wires next.. Also, discussing dash options - maybe have Broadfield install Speedhut gauges OR get a MoTec / AiM dash custom installed in the dash opening...

This is turning into a fun project..

Gator Bait

Have you considered the passenger side firewall under the dash for the ecu? That is where mine is located.

Please post pics of the wire harness hiding process. Cleaning up my engine compartment is a task scheduled for next winter. Interested in the various solutions.

porschelou

Hey Gator Bait -
We are keeping the heater box in the car so the passenger side area has limited space. Did you put yours down low? In the NC car there is a plastic foot piece that takes up about 4" ( fills the foot area in-front of the firewall). Did you put yours there?

I'll take pic's once I start wiring. Been talking to guys at Currentperformance.com - they said they can make a harness to route the ECU any place I want to place it.

Gator Bait

Sounds like about the same spot. Though I can't take credit, mine is FM build. It's "Bert" if you look at their build diaries. You may get some ideas if you go through a few.

Flyin' Miata : Build diaries

charchri4

Can't you tuck it behind the bumper cover or make some sort of nice looking cover for it under the hood?

If you want to put it in the trunk that's not a big deal just cut the computer plugs off and extend them 6 feet. You need about 125 pieces of wire 6 feet long and for that just go to the old Miata harness. It doesn't really matter what the colors are but you should be able to come close to most of them.