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1g Wiring harness and ecu

So I keep reading on the forum about not being able to use a 1g wiring harness and the Ecu's are different. But nobody gives a clear reason why. I understand some pins are different between the gvr4 and 1g Ecu's. I know that the wiring might be slightly different in location and in length.

But what makes the 1g harness not work. Using a 1g ecu would eliminate the problem with the pin location, and the wire length could be fixed rather easy.

So, is there anything that makes this not worth the time.

Heres the reason I want to use the 1g harness....Brand new.... /ubbthreads/images/graemlins/smile.gif

It would be easiest for me to use this harness rather than try to source a vr4 harness. So I need some help here.



Well-known member
Apr 28, 2006
bartlesville, ok
If your doing a complete change over to a 1G harness and ECU, you should also be changing over to 1G compatible sensors, i dont know specifically what sensors are different, or if they even are. some i know are the same. But the wiring was designed for a different vehicle, so the structure of the wire could be built to different tolerances.

My advice, is research the components between the 1G and the VR4 and if the components match, and will work without modding the harness, then you should be fine. i run a 1G ECU in my car, and i only had to change like 2 wires i think... maybe 3, so the differences are that great, if no-one can give documented reasons for why it wont work, and what will be affected, then throw it in and drive on /ubbthreads/images/graemlins/smile.gif

C. Fullwood, Out!


Well-known member
Oct 23, 2004
St. Charles, IL USA
As far as I know only the MAF is different from a sensor perspective but the wire routing could be very different.
From an ECU perspective only 90 ECUs have different pinouts (two pins, 6 and 14 swapped) but the DSM and GVR4 ECUs differ in their software.
Last edited:


Apr 30, 2006
^^^ exactly right! /ubbthreads/images/graemlins/smile.gif

It will do the job with a little work, and several locals have used the 1g harnesses when upgrading a Galant GSX to a turbo motor.

The vr4 engine compartment is layed out a little differently when it comes to some emissions stuff, but all the same components are used, just different locations.


Well-known member
Jul 5, 2006
Stantonsburg, NC
I'm almost positive that a few (if not all) of the connectors where the engine harness mates the dash harness are different. Also some of the connectors for the AC are located in the engine harness and the lines and sensors will be in different locations so if you plan to keep the AC there will be some modification of the harness required. The ECU is in a different spot as well.

If you are good with wiring I'm guessing you could mod the dsm harness to work fairly easy but it won't be a plug and play deal like another GVR4 harness would.


Well-known member
Jan 14, 2009
Lubbock, Tx
Im going through this right now. I thought it would be plug and play, just different location of the connectors in the dash area. Not the case. /ubbthreads/images/graemlins/frown.gif the 1g harness I have has 3 white connectors inside the car that I have no clue where they go. Im thinking this is where the differences begin. These connectors, I think, are what supplies the ecu with power and sends all the signals to the gauges in the cluster.


Well-known member
May 28, 2003
if you're down with completely rewiring it all, go for it! otherwise, wires are paired differently and plugs are different between chassis-engine bay - interior connections.

if you're going for a stripped down bare essentials car, with only the minimal amount of accessories and etc, go for it.

if you're trying to retain full use of everything in a nice orderly manner, not a good route to go, better to sell that minty harness to some midwest DSM kid looking to rid himself of wiring woes.
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