HOW TO: Wire ECU for H22 swap - Honda Prelude Forum
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Old 03-25-2003, 11:47 PM   #1 (permalink)
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HOW TO: Wire ECU for H22 swap

Never got around to adding this to the "big" H22 swap thread untill now. Figured I'd post it here, as well as add it to the walkthrough( which should be pretty much complete now, as far as I know). Enjoy. . .


The ECU is located in the passenger-side footwell. You will need to remove the floor mat, pull back the carpet, and remove the large silver plate that the carpet exposes. . .keep unbolting things till you find it. If you can't identify, locate, and get to the ECU without pictures and specific instructions, I'm suprised you made it this far.

Swapping an H22 into an h23-equipped car, you will need to add:
  • VTEC solenoid, (signal=Green/Yellow to ECU Pin A4 )
  • VTEC pressure (oil pressure), (signal=Lt blue to ECU Pin D6 )
  • VTEC pressure (oil pressure), (ground=Black/Red )
Swapping an H22 into an f22-equipped car, you will need to add:
  • The wires listed above AND. . .
  • Knock sensor, (signal=Red/Blue to ECU Pin D3)
  • IAB, (signal=Pink to ECU pin Pin A17 ), (power=Blk/Yellow to 12v+ switched power source (hot with key in "on" or "start")

The pin locations above are in reference to the standard OBD1 Honda Pinout diagram (which is the same for all OBD1 Honda/Acura vehicles: Preludes, civics, teggys, etc):


In an ideal world, you would be able to obtain a few extra ECU pins to crimp onto the wires you will be adding. Unfortunatley, the dealer does not sell these individaully, so you are gonna need to find another way to get these signal wires into the ECU connector. There are 2 options:

OPTION ONE: THE GOOD WAY
Obtain an OBD1 ECU connector with several inches of wires attached. This could come from any OBD1 vehicle, a junkyard would be a good place to start looking. I have HEARD that the pins from a radio harness MAY work, but I cannot confirm this. . .do note that there ARE different sizes of pins used in the ECU connector (larger ones one the sides of each plug).

Liberate the plugs/wires from their connector. A swift blown with a hammer should do the trick, or you can try and use a little finesse and pop open the back and work them out. Honda sells a special tool for this, but it probably costs $20.

Solder/heat-shrink the pins/wire stubs onto the wires you feed into the cabin from the engine bay. Use more finesse to re-insert pins into correct positions (according to diagram above). THIS IS WHERE LABELING YOUR WIRES BEFORE FEEDING THEM INTO THE CABIN PAYS OFF BIG-TIME, ESPECIALLY IF YOUR WIRES ARE ALL THE SAME COLOR!!

OPTION TWO: THE "I WANNA DRIVE" WAY (a.k.a: "ghetto way"
If you are like me, you are itching to drive your car, and the nearest junkyard is 90 minutes away. Or maybe the term "finesse" in option one scared you off. Fear not: Twist and Jam method to the rescue!

Strip the ends of your wires that you fead into the cabin from the sensors. Twist the stripped ends as tightly as possible. Insert the wires through the itsy-bitsy holes in the ECU plug, so that the stripped/twisted wires are in the same place as the pins would normally be. This may take some toying with, and you may have to adjust how much of the wire is stripped.

Once you have "twisted and jamed" all the wires into their correct positions, double check to insure that none have slipped out, and then tape the wires into the main wiring harness to secure them. Reconnect the ECU plugs to the ECU.

AND THEN. . .
BEFORE bolting the ECU back in place, installing the cover plate, and putting the carpet back in place, turn the key to the "on" postition (not "start"), and see if you get any check engine lights. If you do, jump the service connector and look up the codes in the Helms (you did by that Helms manual, didn't you?). Do note that VTEC codes MAY not show up untill the car is drivable and has been run to a point where the VTEC system would engage.
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Old 03-26-2003, 02:01 AM   #2 (permalink)
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i vote for faq

handy information
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Old 03-26-2003, 07:08 AM   #3 (permalink)
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Quote:
Originally posted by aZnLuDeR82
i vote for faq

handy information
It's already been added to the H22 walkthrough contained in the FAQ.
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Old 03-26-2003, 10:57 AM   #4 (permalink)
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You forgot OPTION #3. (assuming you have a 4G Prelude)

Hook up the VTEC solenoid wire to the little blue connector that goes no where, on the passengerside strut tower location. And then you can hook up the pressure switch directly to the wiring harness under the hood (less work, better connection)

And ground the ground wire to the frame. LOL!

(I found this out when I was doing my H22a4 swap in a 95 4G Si *USDM*) The wiring harness already had pins in the locations listed, so I just traced them back to under the hood and hooked it up from there. No need to drill a hole in the firewall or try and locate a grommet.
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Old 03-26-2003, 02:25 PM   #5 (permalink)
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H22a_Assasin: not all 4th gen were pre-wired for VTEC
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Old 03-26-2003, 04:51 PM   #6 (permalink)
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It should still be added there and put in brackets (for already vtec wired preludes)...cause that will come in handy for sure!
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Old 03-26-2003, 09:23 PM   #7 (permalink)
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Non-VTEC 4th gens that are pre-wired for VTEC are an exception, not a rule. It almost seems as if the factoryt just ran out of the non-vtec harnesses for a while and switched to the VTEC ones. If someone can provide pictures of the "blank" connectors, I'll be happy to include them. However, I'm unsure is ANY "S" models ever came pre-wired for VTEC; and if they did, I'm also unsure if the IAB and Knock sensor wiring would be in place also.
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