Page 1 of 2

ST185 - 185 JDM swap, wiring question

PostPosted: Sun Jan 02, 2005 2:48 pm
by Kappa
Are the wiring harnesses for the JDM and USDM the same? or does it need to be rewired. I KNOW I'll need to extend the harness, but other than that?? Does it just plug into the JDM harness and the car comes alive? or will I be hunting wires for hours like a 3rd gen MR2 swap :-)

Thanks for any info at all! =] My clip is almost here.

PostPosted: Sun Jan 02, 2005 4:41 pm
by illGT4
depends on the years.

PostPosted: Sun Jan 02, 2005 4:47 pm
by Kappa
is there any reference point that i can look at??

PostPosted: Sun Jan 02, 2005 4:52 pm
by illGT4
The pins.

In other words. You have three plugs that must go into ECU.

Let's call them plug 1, 2 & 3 for these purposes.

Plug 1 has X pins
Plug 2 has X pins
Plug 3 has X pins

Use this for reference. If both USDM and JDM harness is from ST185, then you should be okay, if the number of pins are equal.

PostPosted: Sun Jan 02, 2005 7:40 pm
by Keoni
The wiring harnesses are only identical at the ECU. For example I am using a USDM ST185 harness with a JDM ECU on a JDM motor. The 3 plugs are identical between the USDM and the JDM ECU. If you have a USDM harness already,reuse it and it will save alot of time b/c you wont have to extend any wires, just plug in the JDM ECU into the USDM harness and you should be good. Although, a JDM motor doesnt have the EGR sensor so that wont be plugged in. Here is a Pic of a JDM ECU from a SW20 MR2 Turbo that I am using with a ST185 USDM harness with my 1990 3SGTE Celica GT-S swap:


If you notice I do not have the middle sized connector plugged in, the motor will run without it perfectly fine. The only pin that I tapped into is the CEL pin to check for engine error codes.

What are you planning on doing? JDM Motor swap with a Celica All-trac, MR2 Turbo, or a 3SGTE swap into a FWD Celica?

BTW I am from Kailua, would like to meet up sometime!


PostPosted: Sun Jan 02, 2005 7:41 pm
by Kappa
i don't have the USDM harness for my car. It came with a quite empty engine bay... I guess we'll see what happens. Is there an easy way to get wiring diagrams?

Keoni - Thanks for the info! I am getting a full celica front clip. I have no harness so I'll have to extend it anyways. Actually I forgot to change it, but I just moved back to Pennsyvlania, where this all trac has been sitting for a few months. Sorry. It's a shame I couldn't have got a hold of you like two months ago. Oh well, when ever I'm back at the island, I'll definitely look you up. check me out.

PostPosted: Sun Jan 02, 2005 10:08 pm
by alltracman78
Keep in mind the 90/91 harness/ecu is different than the 92/93 [at least for US models]. I can't say if JDM is different also or not.

Here's the US ecu pinouts for 91-93.
FYI- the connector diagrams are upside down from how you'd look at them [clip is on top in diagram, instead of bottom].


PostPosted: Sun Jan 02, 2005 10:38 pm
by Keoni
Thats too bad that you moved...but anyways, if you are getting a front clip then you should just swap EVERYTHING how it was in that front clip. There are 2 ways:
1) You could cut a hole in the firewall above the shifter cable exit/entry and feed the harness to the ECU. Then you will need to extend 2 plugs to the passenger side for the ignition plugs right by the Power steering pressure hose. Everything else should plug right in.

2)You could extend the part of the harness about 33" so that it will enter/exit engine bay in the stock location of the USDM harness. This is probably the route that I would go. Make sure to use soldering method and heat shrink wrap all connections.

The only things that I am not sure about are the Fuel Pump Relay and the Fuel Pump Resistor Pack. If you have a ALL-Trac then I dont think that these will be a problem. But since I have a GT-S , it didnt come stock with these components so I had to figure out how to get around this.

There is really no BIG difference between the JDM and the USDM harness, just the location of where the wiring harness enters/exits the Engine Bay.

Good luck,

PostPosted: Sun Jan 02, 2005 10:47 pm
by Kappa

Thanks for the info. Yeah I have a stock all trac, i really just need a motor, turbo, and wiring harness. However people want ridiculous money for that stuff, and i ran into some good deals on clips. Too bad I didn't catch u when I was on the island. I worked a circuit city in the roadshop, so I met a lot of car people. Do you knew Courtney and his brother Kennedy w/ the ST182s? Kennedy's is pink? Courtney's is like burnt orange?

PostPosted: Tue Jan 04, 2005 4:00 am
by Keoni
Ive seen the pink one in the circuit city parking lot. Doesnt those celicas have body kits?

If you got a clip you could swap in everything and have that all-trac running quickly. You will definately notice what goes where and what plugs into what, its easy with a Clip. Wish I had been smart at the time and bought a front clip, took me over 1 year and a half to finish my swap.
I would have also gotten the sweet all-trac hood.

Good luck with the motor swap! Let me know if you have any more questions.


PostPosted: Sat Mar 19, 2005 6:57 pm
by BanhBaoBao
sorry to dig a topic out of the dead but i need some clarification=)

I have a USDM 90 Alltrac and will be putting in a 92-93 JDM motor. Which harness/ecu combos would be possible for my car including mr2 combinations.

EDIT: To clarify a little, I have a 90-91 harness but a cut JDM 92-93 harness/ecu. Would I be able to use the 90-91 harness rewired for the 92-93 ecu? Such as would the connectors on the engine side of the 92-93 JDm engine match my 90-91 harness? Thanks.

PostPosted: Sat Mar 19, 2005 9:03 pm
by ChrisD
The connectors on the engine side would match, however, the connectors at the ECU would be different. You can rewire the harness to match if you wanted.

PostPosted: Sat Mar 19, 2005 10:39 pm
by BanhBaoBao
Thanks a lot! Thats what i was hoping for. =)

PostPosted: Sun Mar 20, 2005 4:28 am
by BanhBaoBao
on second thought one more question =).

Would it just be easier if i used a 90-91 ecu? then i dont have to rewire anythign right?

PostPosted: Sun Mar 20, 2005 7:36 am
by ChrisD
Yes, that would be easier. That said, I've learned I can convert over my ECU pins in under an hour, so its not too bad. :)