jcb111

I just did this my 2005 Civic LX (non VTEC) blew up and replaced it with a 2003 Civic EX VTEC Motor, Trans, wire harness and ECU

Some of the wires are a little different between the 2
There are differences between the Motor harness and the body harness.

All good after flash from Honda
Keys work now with the ECU that matches the motor need to do this if you change the ECU. The motor ran on the LX computer just thew codes for the O2 sensors.
Only code its throwing was the heater on O2 sensor 2 which if you get the harness from the motor there is no place to connect the Downstream O2 sensor as the exhaust is different between the 2 motors. I changed my exhaust also, used a aftermarket LX header back exhaust and just added the 2nd O2 sensor about mid car and left the plug in the header for O2 number 2. You will also need the O2 sensors for the EX motor as they are different between LX and EX
Wired the Black/Yellow wire to pin 5 yel/blu on connector E
Wired all O2 stuff to connector E and all good now, No codes

So just so its cleared up for anyone else doing a LX - EX conversion in a 2001-2005 Civic here is where the wires are landed when using EX Motor, Trans, Wire Harness and ECU

Here is where they are on the stock harness Connector A (31 pins)
25 wht/red Secondary O2
23 brn/yel Logic Ground
14 blk/wht SecondaryO2 sensor heater control
10 grn/yel Sensor ground
Blk/yel Heater acc power

Here is where they go on Connector E (31 pins)

2 wht/red Secondary O2
3 brn/yel Logic Ground (Shield from O2 Sensor)
5 yel/blu Sensor voltage (attach to blk/yel from O2 Sensor)
6 blk/wht SecondaryO2 sensor heater control
Connector A (31 pin)
10 grn/yel Sensor ground

On the wht/red and Blk/wht
I dissected the old harness to get the whole wire with the metal ends that fit into the harness. As you will find out when going from LX to EX there are a few different wires and they are not in both body harnesses the same way. On the other wires I just tapped in and soldered and taped as not to cut the factory wiring.
I hope his helps anyone that might be doing the same swap that I needed to do to get my everyday driver back on the road with a few upgrades.

sdaidoji

iTrader: (1)

jcb111,

pretty good instructions for wiring a VTEC engine - worth making it a separate thread and sticking it to the top

thanks!
moderators

jcb111

Thank you 😀

RER747

Further to JCB111's post.
Connector A is the grey connector and connector E is the white connector.
Attached is an image for the connector E wiring:

Pedroflow

are you guys from california?

jcb111

Jimmy_p27

Sorry for this but did you cut from one connector and soldered them to the other connector cuz I. In the middle of doing the same swap and a lil lost

NinjaPete

Do you have a picture of the o2 sensor you added. also what o2 from the Ex do I have to get. Is it the up stream or down stream. Thanks for your time.

supramaniac311

Hi there, I have a 02 civic lx with a blown non vtec d17a1. I purchased a jdm D17A vtec engine/trans swap with harness. I'm having some trouble wiring in the second o2 sensor. Your post was very helpful, I just have a few questions. You said the wires for the secondary o2 sensor go into the small white plug, Instead of the small grey plug? Also how do I add the wire to the slot if there is already a wire in the slot? Should I wait to do this whe. My new motor is in the car? It's still on the pallet. Is it possible to erase the o2 sensor code with an xtool to avoid having to wire in a second sensor? I have an xtool x100 ecu programmer that can erase codes. Any help with my project will be much appreciated. Thanks

jcb111

With the JDM motor you have to swap a few other parts over from your existing motor. I forget exactly which ones I moved over.

I had a Donor harness with my new motor and I cut the wires out of the old harness to use in the new locations.

As far as programmers I know nothing. I had Honda flash my new computer to work with the new motor.

Please note I had a D17A, wire harness and ECU from and EX model car

If you do not have an EX ECU your vtec will never kick in. The car should still run on the LX tune just not as good. I drove mine to Honda with the OLD ECU in and at Honda replaced the LX ECU with a EX ECU

As far as the harnesses to a search on the forum thats how I figured out which ones to use. I know someone has posted picture of the plugs for this process. I used to have pics of the harness and plugs but that was a long time ago.

Hope this helps

Slumpertcivic

Move your wire harness to the new engine.

Your engine likely does not have a EGR, does the new one have it? Might need to move your intake / water passage to the new engine.

Your alternator works, move it to the new engine.

Transmission is a hard one, new one will cause concerns for your PCM as the gearing is different and the PCM will think something is broken look for all the work arounds.

Move your timing belt, tensioner spring, and water pump to the “new” engine or even better replace then with new parts.
That JDM engine is 15yrs old and the “low mileage” claim insures that those parts were never replaced since it was made.

OG40

Hi am in the middle of trying to figure this out i've been reading your post over and over trying to understan it mine is a 2001 civic lx non vtec and I swap it with a vtec engine I have the vtec harness and ecu right now am running it with the non vtec ECU the only code am getting is for secondary o2 sensor , should i be able to use your rewiring metod if I keep the stock exhaust and header or do i need to purchase an after market exhaust, I should of just gone with the non vtec engine it would of save me all the headaches lol😀...should I retrieve all 4 WIRES from the non vtec harness and transfer them to the vtec harness ?? BTW Your instructions are very clear is me who is confused with all the wires.

jcb111

Your car will run on the non vtec ECU, your check engine light will stay on and yes it will throw a secondary O2 Sensor code because that ECU is not wired the same way. You can get all your wiring in place and then drive the car to a Honda dealer for the key flash, take all of your keys. When you get to the dealer swap out your ECU with the vtec one and have it flashed. you should be fine after that if everything is wired correctly. You can keep your stock exhaust and it should work but you need to weld a bung in just past the CAT for your secondary O2 sensor to wire in. And yes if you didn't want headaches you should have done a non vtec motor but what fun is that. The car is still running strong BTW my son still drives the **** out of it without a problem.

kwscott84

1. 
   Are you talking about the actual ex wire harness or is this the original body harness, I’m in the process of switching my exact car over.

jcb111

I used the EX motor harness and the LX body harness. I cut up my old LX motor harness to get the downstream O2 sensor harness to wire in.

kwscott84

right on! I’m using JDM motor, trans, ecu and harness.
my JDM motor doesn’t have a pressure switch next to the Vtech solenoid, do i need to add pressure switch?

jcb111

Yes you need to swap one to the JDM motor. I also swapped a few other parts from the EX motor but don’t remember exactly. I had a USA Ex motor for parts.

buckou812

So did you use factory LX upstream o2 sensor and factory ecu pin locations for the upstream? And then use factory EX downstream o2 sensor wired to connector E?

jcb111

as I remember. I had the ex harness from the doaner car.

i dissected the LX upstream wires from the LX harness.

tapped that into the EX harness for the Downstream O2 wires.

Please try and follow the instructions as posted.

i don’t have this car anymore so I can’t go check to verify for you.

also bought 2 EX O2 sensors. The LX ones will not work

hope this helps