hi guys, feel like a noob for asking this, but i have searched and searched, and i am pretty sure i know whats going on but i am so ocd that i need some other input. so i have a 90 crx si, that i am swapping a z6 into. i bought a p28, and a conversion harness. i have a four wire 02, blah blah blah. so the conversion harness didn't come with a list of pinouts or instructions. no biggy i figured i would just use diagrams, and cross reference stuff, so i got all the wire colors and pin outs (listed below), now it seems that there are three or so extra wires (not for knock sensor, or butterflies, or check engine, although those are there) so the three extra wires i believe are all ground wires. i have tried following the diagrams from my helms manual and it just shows them interconnected inside the ecu, so knowing if i need to hook them up to anything (ie. sensors and so on) is kind of baffling me. on the conversion harness two of the wires are black, pin out (a23=pg1 power ground, and b2=lg2 logic ground) the third wire is brown, and it is pin out (a26=lg1 logic ground) do i have to use these three wires and add them to my existing harness, or can they be just snipped off or tapped up. do they provide ground to the knock sensor, IAB or vtec pressure switch? i dont know. every guide i have found always just says. ie. body ground, and does say which pin from the ecu provides the ground. thank you for your help. also before you say search, i have been through countless guides, including this one. https://honda-tech.com/forums/honda-...-vtec-2987229/

the colors and pin outs my conversion harness came with, in the exact orientation/order of the plug it came with.

Purple- A4 - Vtec Solenoid valve
Blue - A6 - Primary o2
Green - A17 - IAB (not used)
Black 1 - A23 - Power ground 1
Red - A25 - IG2 Power source
Black 2 - B2 - Logic Ground 2
Pink - B1 - IG1 Power source
Brown - A26 - Logic Ground 1
Orange - D3 Knock Sensor (not used)
Yellow - D4 - Service Check Signal
Grey - D6 - Vtec Pressure Switch
Grey - D14 - Primary 02 heater sensor


also i have one question pretty sure i know the answer i just want to confirm. which plug is this? it is from the stock engine harness of my crx si, it is on the back of the engine, and believe plugged into part of the emissions stuff i think on the ef intake manifold. which i am scrapping, so i am pretty sure it is going to be unused but just wanted to make sure. again i searched couldn't find an answer sorry. thank you all for your time.

 

Regarding that mystery plug, supposedly it's for the fast idle control solenoid. It doesn't exist on my B swap so I've left it unplugged with no issues. For the ECU conversion harness I'm not entirely sure about your question but my kit did have I think 3 ground wires I used for my needs (vtec, O2, VSS if I recall). My kit instructions don't go into specifics on ECU pins used for this.

 

like you don't know the answer to my question, or you don't know what i am asking? maybe i will try clear things up a bit. the wire colors and pinouts i mentioned above are the ones that came on my conversion harness. i guess as simply put as i can, i am wondering which ones have to be hooked up in order for the swap to work. i know the o2, and vtec, it just seems odd to me that the harness would come with these extra wires. i know it's probably because when they mass make these things they do it so they can cover more than one engine, and vehicle. so i just want to know which ones i need to hook up and which ones i can just tape off. when i cross reference my harness to say like a ry-wire one it has has two extra wires. the rywire ones have ten extra wires that are spliced into the harness, mine has 12. mine is pictured below.

 

Ah OK. My conversion also had the 12 extra wires and I'm using 10 I believe. The ones I'm not using are IAB and SCS. The rest are used for O2 4 wires, VTEC solenoid and pressure switch (3 wires total), knock sensor 1 wire, and I think I used 1 power and 1 ground for my electronic VSS. The colors on mine are very similar to your picture, so on mine the yellow and green are unused pretty sure. Not sure if that matches your kit though...

 

ya my kit the yellow and green are not used as well. how did you ground your o2, and vtec pressure switch? looking online it says to ground the o2 to pin d22, however my conversion harness didn't have an extra wire coming off d22, only the three mentioned above. so its like does it matter? in the manuals and stuff they are called logic ground and power ground. to me one sounds like the logic board ground, so for the ecu, the other sounds like just straight up power ground. but then when i look at pin d22, it says signal ground. if i wasn't so ocd, i would just use trial and error, but i also dont want to fry my ecu.

 

Here's the guide that came with my unknown brand obd1 conversion:



So this included two power and three ground wires as needed for my sensors. I have no information on which ECU pins these correspond to so I just used them as I went. It seems to me like they might share a single power and ground source but I'm not sure. My two power wires go to O2 and VSS, and the three grounds go to O2, VSS and vtec.

 

k thanx man, i am pretty sure we have the same harness, so i am going to go with the above. i just traced the wires on the plug to get the ecu pinouts. thank you for your reply man.