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03 5AT Engine/Tranny ECU & Tranny Electrical Connector Issues Need Help Please
If anyone can answer this question for me, I would be so grateful. Or any advice at all would be much appreciated.
Blown engine at 120kmiles and tranny was at 180k miles is the reason for the engine/tranny swap. Decided to replace both because I found at JDM New York a new engine/tranny/ECU engine harness with only 45kmiles for $1900 with delivery. I took out old engine and tranny together, and put in new engine and tranny together. Everything has went smooth during the swap but now that I am at the end of it all I am running into an issue and am praying that there is an easy solution out there.
Problem I’m having is I have the early 2003 sedan with the old style grey ECU as well as the old style transmission electrical connectors with the 3 green connectors that join as one and go into tranny. (I believe its the external TCM). The new engine and transmission that is now in my car has the wiring harness that goes to the newer ECU, which it came with but it is JDM ECU not USDM. As well as the new transmission has the newer single plug in for the electrical connector. I am perfectly okay with continuing to use my stock grey ECU and wiring harness because it connects to engine at all connections but how would I get this harness to plug into the new transmission? Can you get the 3 green connectors to plug into the new single transmission connector. Or is there a way i can use the new engine harness which works with new transmission to plug into the old ECU. I don’t know what my best or easiest approach would be.
But the whole swap is done just need to get a harness to connect to my ECU (old grey version) and to my transmission (new 1 connector version)
Also, I will attach pictures of connectors and ECU’s and supply old and new engine and tranny model numbers here shortly. Thanks again for any answers or advice.
NEW ECU OLD TRANSMISSION CONNECTION NEW TRANSMISSION CONNECTOR (TOP OF THE PICTURE) MODEL & SERIAL NUMBERS (OLD & NEW)
Last edited by MWeis; Jul 18, 2018 at 10:54 AM.
Reason: wanted to add more
You can swap the TCM and harnesses, the green plug tranny has the external TCM which sits next to the ECU in the cabin. The grey plug tranny has the TCM on the back side of the valve body.
Edit: swap the old style valve body and wireing harness, the harness grommet pops out so you can put the old wires back in.
Look up a DIY on the transgo shift kit to see how it all comes apart.
Last edited by cleric670; Jul 19, 2018 at 10:23 PM.
Does my new tranny grommet pop out? The one with the single snap on connector? Cuz if it doesnt then ur saying use the new engine harness which in that case I would need to use new ECU. Sorry just want to clarify what youre saying I should do. And would changing out TCM require any rewiring of the engine harness.
Ok I watched some DIYs on swapping out the valve body. Do you think the best route is to use original harness and ECU and just take the valve body off of my old transmission and change it out into new transmission. That way my harness connects to it.
Ill fix the double post issue. So old grommet will fit into new grommet hole? Then just switch out the valve bodies? Thanks for replying much appreciated.
Yep exactly, once you get the big plug out of the new transmission you'll see the hole is exactly the same and the old grommet with the 3 wires fits right in.
Right on so just swapping out the valve bodies will solve my problem? Thanks. Also do you think its ok to be running the external TCM valve body with the transmission that is meant for the internal TCM
Found several articles describing in detail both types of valve bodies that I have in the two transmissions. And it says theyre not interchangeable. Because even tho old wires can fit into the whole where i would place the grommet in place of connector the wires wouldnt match to connect to valve body. Pretty much saying that old valve body wont work with new transmission...idk looks like i may need to do more research or just wait until JDMs tech guy calls me back
Ok, just went through this with a different user a couple months back and it worked out fine. Your existing valve body and wiring harness should fit into the newer transmission.
Aside from the internal TCM the only changes were various vendors for the solenoids and other internal components, everything meets the same spec though. Typical of every transmission manufacturer not just Jatco, overall there's something like 12 revisions to the 5AT but almost all components are completely interchangeable.
If you're hesistant that's fine, but it's been done recently.
If you suspect your original original valve body is DAMAGED however that would be a problem.
Edit: talk to text will be the depth of me... EDIT: DEATH DAMMIT!!!
Ok after re-reading the thread I caused a little confusion. You CANNOT mix the old and new TCM and valve body. You either use the old valve body with old TCM or new valve body with new TCM.
Edited post 2 to clarify.
You will remove the new grommet/wires/valve body/TCM and replace it with the old grommet/wires/valve body. Your TCM stays in the cabin.
Right on. Yea i knew the TCM wasn’t interchangeable. Just wasn’t positive on running old 3 wire connections through new transmission even with the old valve body. But i trust your judgement and thank you for bringing me good news. I will take off new valve body with internal TCM as well as the new grommet connector. I just ordered a brand new engine harness that is identical to my old one and I still have my original ECU and external TCM by right side kick panel. I will run my harness through engine, ECU, external TCM and into old valve body and new transmission. Then I will update you on here on how it all went. Thanks again
Sorry to bring up an old post.
But I am kind of in the same boat here.
I swapped my 2003 5AT Tranny and motor into my new to me 2005 sedan.
my 03 trans has the 3 plug connector.
I am using the 2005 engine and body harnesses because it was all good to go. Just drop my motor and trans in and go. So I thought.
Do I need to purchase a 2005 valve body and connector to get my 2003 tranny to work in this car?
the 3 plug connector has 20 wires and the 2005 harness only has 10 wires going to the tranny.
And none of the wires are the same colors ugh.
You can keep the valve body and TCM from the existing 2005 tranny, it will also keep the single 2005 plug it just pops out of the transmission housing.
Look up the installation instructions for the Transgo shift kit to see how to disassemble the valve body+TCM, it's very easy, just a lot of bolts and you want to make sure to keep things clean.
Your existing 2003 tranny the TCM was mounted next to the ECM in the cabin, the newer transmission the TCM is inside the transmission bolted to the back of the valve body, they remove as a single unit, and thus the extra wires on the harness.
03 5AT Engine/Tranny ECU & Tranny Electrical Connector Issues Need Help Please
