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PostPosted: Fri Apr 24, 2009 12:36 am
by siralys
Ok so I have a 165 and want to run the 185 ecu. I know someone with an uncut jdm 185 harness and ecu, if I got the full 185 harness couln't I just put that in instead of getting an adapter harness?

PostPosted: Fri Apr 24, 2009 12:44 am
by aubeone
Yes and no.

The plugs arent the same on the engine, so you would have to change them all over.

In your case I would just adapt the harness for the ecu.

PostPosted: Tue Jun 23, 2009 5:18 am
by xCH121Sx
i got a hold of a trashed gen 2 harness from a friend. so i have the male plugs for the ecu.

i was thinking. everyones adapters are just in case their wiring was bad they can revert back to the 165ecu.

no ones had problems so far.

i was thinking since i dont have the female part of the ecu that i could solder new plugs directly to the 165 harness.

anyone see why i shouldnt do this?

PostPosted: Tue Jun 23, 2009 11:50 am
by aubeone
In all honesty, after completing the adapter and mounting everything I ended up just swapping the plug ends anyway...I found the adapter took up way to much space in an narea where space is already a non-existent commodity.

Quick question also:

Has anyone come accross the situation in their swaps where there doesn't appear to be a match for the coldstart signal (STJ)??? Both the original 165 harness that I am using and the JDM 185 engine have cold start valves, but the ecu for the engine doesn't have an STJ signal/pin/wire....any ideas?

PostPosted: Tue Jun 23, 2009 2:57 pm
by Dr Tweak
JDM ECUs don't have an STJ pin.


PostPosted: Tue Jun 23, 2009 4:51 pm
by aubeone
Noted, would one wire the cold start injector then? Or do you just skip it all together?

I guess what I am looking for is guidance. What is the appropriate way to wire in the cold start on a jdm (185) engine with a usdm (165) harness?

PostPosted: Tue Jun 23, 2009 5:08 pm
by Dr Tweak
It's not really a big deal, the injector is turned on by the switch. On our harnesses I have the wire there in case a USDM ECU is being used, otherwise it isn't used at all.


PostPosted: Tue Jun 23, 2009 5:12 pm
by aubeone

So if I leave it alone, it'll do it's thing?

Thank you.

PostPosted: Sat Sep 26, 2009 4:59 am
by All4Traction
Cool to see this thread is still alive.
Honestly, this was years ago and a lot of it is jibberish to me again. :(
Miss my car, hope this has helped a few people get their cars running good on the road :)

PostPosted: Sat Sep 26, 2009 5:58 am
by Rick89GTS
Paul, buy another 165! :wink:


PostPosted: Mon May 31, 2010 10:35 am
by jingo11
MXP_57 wrote:Hi, i'm cedric from perth, australia.

I ve got a st165 jdm with a st185 jdm engine. but was still running with the st165 ecu and loom.

I needed to swap to the st185 ecu because 1987 st165 jdm doesn't have fuel cut based on pressure from the PIM. It's measured with the air flow. So i cannot boost more than 10 psi.

I plugged everything. The car start, but the air fuel ratio is lean, and there is black coming out of the exhaust when i accelerate. I didn't test drive, just idle. Code error 32 ( open circuit on E2 or short between vc and vs.)

Could you tell me how did you do to plug FC and OX2 ?
Could it be because there s nothing plugged in PIM?

Thank you very much for your help, i 'm a bit stuck...


Did you sort i have the same ECU with no PIM etc and am in process of converting to a link g3 ecu though need to convert ot MR2 ecu wiring plugs due to connectoors... most done but any elp appreciated Image


Re: ST165 to ST185 ECU Conversion

PostPosted: Sun Dec 05, 2010 8:03 am
by xeril
So, I have a AEM EMS on its way and I've been looking at this. This appears to be how it should be wired up (according to the standard pin-outs I've seen on diagrams and what AEM seems to believe the standard wiring is for a 90/91 ST185 ecu.)


I haven't been able to find anyone else using an AEM EMS on an ST165 block so I guess I'll let you all know the outcome, though I don't see any reason why it shouldn't work.


This appears to be the price list to for connectors to make TWO (2) harnesses for a ST165 (52 pin female plug) --> ST185 (3 male plugs 26, 16, 22 pins) ecu from They offer a minimum order of 35$, so they add money to bring the cost to 35$ if your order doesn't contain that much in parts, so you might as well order two sets.

Re: ST165 to ST185 ECU Conversion

PostPosted: Wed Nov 28, 2012 1:12 pm
by 3-S-G-T-E
old thread revival!!! I have just purchased an old st165 rally car, which campaigned in Group N in the UK in the early 1990s.



It currently has an st165 ECU/AFM and loom with an st185 engine. I have an ST185 RC ECU/AFM which I want to use in the car with the st165 loom - is this possible??? Anybondy know what do I do about the lack of FC on the 165 loom and different AFM connections??

Thanks, Andrew

Re: ST165 to ST185 ECU Conversion

PostPosted: Tue Dec 18, 2012 8:43 am
by xeril
Ahhh thats right, FC is the fuel pump relay (I believe). You could just do the always on fuel pump mod by jumping the two terminals in the diagnostics box under the hood.

I would assume you could find a connector that fits the 185 MAF from some car in a junk yard and cut/solder that plug on in and use it..

Then you'd have to go through the hassle of getting the connectors to use for the ecu and rewire that. Theoretically it should all work; however, I ended up needing cash and selling my AEM back in the day so I never got to try out. Good luck!