A brief summary on where to get 1JZ ECU connectors and how to make
a 'Fields' harness to extend the engine harness for LHD configurations

- or -

1JZ connectors, junkyards, and sore fingers.

Note: at the time of this writing this is **UNTESTED**. I can't see any reason why it won't work but I take NO responsibility if these instructions fry your ECU, blow up your car, cause a nuclear meltdown in your garage, or any other negative outcome.

** See bottom for an important update

Well I planned on this being a nice long detailed page on how to make a 1J Fields harness but time just isn't allowing me to get it done. I had also planned on having this running in my car by now but due to delays in my swap it's still waiting for me to turn the key. Soooo... I will throw up all the information I have at the moment and if anyone has any questions you know where to find me (if you don't, check the bottom of this page)

Goal: To solve the issue of the 1JZ engine harness being too short when used in a left-hand drive car we need to find a way to lengthen it. Previous efforts have been along the lines of cutting and splicing additional wire into the stock engine harness. The potential for error here is great and I wanted to find an alternative way to solve the problem. My solution was to find a way to fabricate a sub-harness that will plug into the end of the 1J engine harness and go the extra distance (about 2 feet) to the ECU.

The other advantage of this method is that it provides a nice clean place to splice in after market electronics without cutting the stock harness. You can remove this sub-harness from the car, place it on your bench and splice away.

Note: this does not solve the issue of the engine harness' body plugs also being too short but that is another issue and I will post my solution to that soon. Email me if you would like a description in advance.

It should also be noted that there IS a small 5th connector on the 1JZ ECU that needs to be extended. I have not yet found a source for this connector but if it was located the same technique could be applied to it too. I noticed that there are only 2 wires on my car going into this 5th plug so I will probably use the old "cut and splice" method of lengthening these for now.

On to making the harness. The first requirement is to locate the necessary connectors for the harness.

Here are the 1J ECU connectors we are looking for:

Female side:

The connectors are actually quite common... they are made by AMP and used on a number of different vehicles. First source I found was on early 90's Honda OBD I ECU's. The Honda's however use a shortened version of the plug as shown below. As you can see the smallest plug is missing from this configuration... however these ECU's are VERY easy to find in boneyards.

Example Honda ECU (early 90's Camry):

Picking up one of these Honda ECU's however provides a great source for spare pins and spares for the 3 larger plugs. (or just go in with a pair of snipers and cut these three plugs off the chassis of a dead Honda... you can probably get em for 50 cents)

Further research turned up the information I was looking for. Below I have compiled a list that covers all (I think) the vehicles that use the same ECU plugs as the 1JZ.

Cars having the same ECU Connectors as the JZA70
Honda/AcuraNSXC30A, C32BAll 
Honda/AcuraLegendC32A, C35AAll 
Honda/AcuraInspireG25A, G20AAll 
Honda/AcuraPreludeH22A91-96With Traction Control
Honda/AcuraIntegraB18CAllAuto Trans Only
Honda/AcuraCR-V (RD1)B20B95 and up 
Honda/AcuraS-MXB20B96 and up 
Honda/AcuraStep WagonB20B96.5 and up 
MazdaEunos Cosmo (All)AllAll 
MazdaRX-7 (FD3S)13B-REW91-95 
MitsubishiDiamante (F36A)6G7295-96MIVEC (not DOHC)
MitsubishiFTO (DE3A)4G9394-96 
MitsubishiFTO (DE3A)6A1294 to present 
MitsubishiEclipse (D32A)4G6395.6 and up 
MitsubishiGalant (EC5A)6A1396 and up 
MitsubishiLancer (CP9A, CN9A)4G6396.8 and up 
MitsubishiLancer (CK4A, CM5A)4G92, 4G9395 and up 
MitsubishiLegnum (EC5W)6A1396 and upDOHC
MitsubishiMirage (CM5A, CJ4A)4G93, 4G9295 and up 
MitsubishiRVR (N74W)4G6397.1 and up 
MitsubishiRVR (N71W, N61W)4G9397.1 and up 
SubaruImpreza (GC8)EJ20G92-96 
SubaruImpreza (GF8)EJ20G93-96 
SubaruLegacy (BD5, BG5)EJ20H96-98 
SubaruLegacy (BC5, BF5)EJ20G89-93 
Toyota/LexusCrown (JZS15#)1JZ-GE95-96 
Toyota/LexusSupra (JZA70)1JZ-GTE90-93 
Toyota/LexusCresta / Chaser (JZX90)1JZ-GE92-96 
Toyota/LexusCresta / Chaser (JZX81)1JZ-GE/GTE90-92 
Toyota/LexusMR2 (SW20)3S-GE93-97 
Toyota/LexusCurren3S-FE94-96with Traction Control
Toyota/LexusCarina ED / Corona EXIVSee CurrenSee Curren 
Toyota/LexusCaldina (ST195G)3S-GE95-97 

There are a couple of problems with the above list. Here in Canada I was hard pressed to find any of the above vehicles in the local wreckers. Some models listed above never made it to North America, and the rest are too new to find in most local yards. (local yards seem to start with cars about 10 years old and older) I ended up searching for awhile for one of the listed models but had no luck... your area might be easier. Option 1 shot down...

I was also having a hard time finding any of the local DSM or 3rd Gen RX7 guys who were willing to hand me their ECU's Also anyone who has one of these ECU's for sale wants a fortune for it as both of those cars are very popular. Option 2 shot down...

Eventually I decided to check out the local JDM importers and bingo... there was my source. I asked to see their pile of spare ECU's and in 5 minutes I found my donor ECU... a Mitsubishi Galant in my case. Make sure if you use this source that the ECU plugs are included with the ECU. Mine had all four plugs with about 3 inches of wire left on them.

My Mitsubishi Galant donor ECU:

How you remove the large one piece connector from the ECU is up to you... personally I found a little hacking with a Dremel and cutting wheel was quite effective... and strangely fulfilling too I then used a solder sucker and cleaned up each of the leads one by one. In the end I was left with a somewhat pristine connector.

Detailed views of the connector still in the donor ECU:

Salvaged ECU Connector:

Cleaning up the 4 little connectors on the other hand is a more tedious issue. After experimenting I found that a set of mini screwdrivers does the trick nicely. At the end of each connector you will find small tabs that when released, will allow the back of the connector to open up. There is a separate locking bar for both the top and bottom rows of pins.

One of the connectors opened:

Using a small screwdriver in the hole above each pin (from the front) you can release the small catch that holds the pins in place. This is what takes the most practice and I suggest if you can, you experiment on a junk connector. The larger pins are very easy but the smaller ones take a little more practice and require a VERY small screwdriver. After a few minutes I quickly became an expert at releasing the pins, however I did cause enough damage in experimenting that one of my spare plugs was now unsuable. The technique I ended up using involves applying a SLIGHT tug to the wire you are trying to remove while lifting the catch holding the pin. You will hear a small 'click' and the pin will slide right out.

Releasing the connector pins: (sorry about the focus)

Each pin has a crimp at the end that holds on to the casing of the wire. This can be easily pried open to release the wire.

Pin with wire:

There is a second crimp that holds onto the core of the wire. This crimp is far too tight from the factory to consider opening up. I found that by bending the wire back and forth it would break off very close to the crimp and leave me with a relatively clean pin to solder to later.

At this point I should note something else.... there are actually THREE different types of pins in these plugs you need to be aware of. They are as follows:

Type 1: LARGE Pin Crimp for LARGE gauge wire
Type 2: LARGE Pin Crimp for SMALL gauge wire
Type 3: SMALL Pin Crimp for SMALL gauge wire

When making your new harness try to use the large pins on the appropriate gauge wires if you can.

After awhile you will be left with sore fingers... new skills with a screwdriver... and a pile of parts that looks a lot like this.


This is where the pictures end From this point I will give the next steps in point form as they are very self explanatory.

- solder new wires to each pin of the large one-piece connector making sure to use the proper gauge wire. I used 20 gauge (for the thin wires) and 16 gauge (for the thicker wires) myself. You should also consider picking up high temp wire to be sure that it will withstand the engine bay heat. There are also a number of pins that use shielded wire in the stock harness. I would suggest that you use shielded wires in the same places the original harness used them.

- heat shrink each of the connections on the large connector individually to ensure there is no possibility for a short.

- cut all the wires to the desired length of the harness. Myself I wrapped it all together first then cut all the wires to length. I then unwrapped the harness and continued. This ensured that when I wrapped the final product all the wires had enough length to make a nice clean harness

- solder a salvaged pin to the end of each wire, taking care to use big and small pins on the correct wires. Also be sure to gently crimp the pin onto the shielding of the wire with a pair of pliers.

- plug each pin in the corresponding location on the small connectors to form a straight through harness. If you're ever unsure remember that if you plug the ends of the harness into itself each wire should form a loop... so if the ends of your wire don't meet up... you have your pins crossed. USE EXTREME CARE ON THIS STEP! If you cross up your wires the results will be unpredictable when you plug this into your precious ECU... but smoke is a strong possibility. BE CAREFUL! Every wire must go straight through. (there... I think I emphasized that enough)

- lastly tie, shield, wrap... whatever you desire... your final harness.

You now have a 1J ECU extension harness. A couple of added notes. I plan on putting the engine bay connections inside a small metal project box on the firewall. The metal box will help to shield the connectors from interference as well as from the environment. (water, etc)

That's it for now... sorry it got rather brief towards the end. I will add further pictures and details as time goes by, but this should provide lots of information on how to make your own harness. I will say though that this is a pain in the butt to do! If I could have bought one I would in a heartbeat as the time involved is probably not worth the cost of just buying one. Originally I had planned to offer these for sale but after doing mine I don't think I want to do too many more. I will consider it if someone wants to make it worth my while though

Final harness:

Also note that at the time of this writing this is **UNTESTED**. I can't see any reason why it won't work but I take NO responsibility if the above instructions fry your ECU, blow up your car, cause a nuclear meltdown in your garage, or any other negative outcome.

Now that that's said... I hope it saves some people a lot of hassle. If you make one of these harnesses please contact me and let me know. It would be nice to hear from various people trying this solution.

**** UPDATE: Why I won't be using this harness ****

Upon test fitting my harness into the engine bay I discovered two problems with where the stock harness ends up that changed my mind on using this extension process.

1. The stock harness ends right on top of the heater core valve, and only a few inches from the turbos and the heatsheilds. The heat, interference, etc in this location make it a bad choice (IMO) to place an unshielded connector of this size... esp for something like an ECU.

2. The proximity of the heater valve means it would be very difficult to box in the connector as I had originally planned. I had hoped to put a small metal box on the firewall to contain the connections, but when I actually looked into the car here just isn't enough room to do it well. The stock harness is too short to reach over to the "ABS" area where I would have room, and around the heater valve is just too cluttered. I really didn't want to have the box end up over the valve covers.

I will leave this page posted for those who are still interested in trying this process... AND it should be noted that this could still be used to fabricate a 1JZ fields harness... however those are getting to be more readily available these days and probably not worth all this hassle. If you try this please let me know how it went and how you solved the above issues.

Contact info can be found at the bottom of my main page here:


The information on this page was put together by Steve Brecht 2002. If you use this page anywhere else please kindly ask my permission and keep my name somehow associated with it. There isn't anything too groundbreaking here but I'd still like to keep track of where it goes as it did take a fair amount of time to compile. Thanks.

Last updated: June 25, 2003