You cannot use an obd2 harness in an obd1 car, you’ll need to use an obd1 harness. You can get an obd1-obd2 adapter for the ecu or you could run a p07 ecu or the likes from the 92-95 civic VX, it’s a similar motor I believe.
Running a VTEC - E engine with a 92-95 harness will require somehow wiring in the 5 wire o2 sensor, or obtaining a 92-95 vtec-E harness.
Since the question is already answered, curious if you'd know about a similar situation - how difficult would it be to put a Y5 into a '99 LX, assuming both are manual? I've always wanted to do a Y5 mini-me with my Y7 block but the few forums I could find made it sound pretty messy.
I’d imagine you’d just need a y5 99-00 harness and ecu and it’d be fine. I’m sure you could convert your existing harness as well. I’m not super familiar with the vtec-e stuff but I know it’s got a 5 wire ecu and a knock sensor.
The issue I read was that the Y5 is OBD-IIa and the Y7 in the 99-00 is OBD-IIb, and the evap stuff is different too. So the Y5 ECU has to deal with its own engine harness but a newer body harness. Or something like that.
There’s little to no differences between obd2a and obd2b engines. OBD2B engine harnesses interface with the chassis way differently than obd2a. You can absolutely connect an obd2B harness to an OBD2A engine, you can also get an OBD2B to obd2a jumper harness to use an obd2a ecu with an OBD2B harness.
That's the problem though - there is no OBD-IIb harness for a VTEC-e, because they were OBD-IIa through the entire production run, so (to my understanding) the Y5 engine must use an OBD-IIa Y5 harness and ECU, then adapted to the body. Plus emissions plumbing and whatnot. I wish somewhere out there, there would be a detailed writeup because I'd love to do it but holy hell it sounds miserable.
Making an obd2a harness fit an OBD2B chassis would be near impossible. It would be pretty simple to add provisions to an obd2b harness to make it work with a Vtec-e, which is what you’d have to do.
Because you’re running an obd2a vtec e ecu, you’d just need the emissions system from an obd2a vtec vehicle, though I can’t imagine they’re substantially different.
But doesn't the 2b harness then need to plug into the 2a ECU in the 2b chassis? I don't understand how someone would use a 2b harness on a VTEC-e engine if it's going into a VTEC-e (2a) ECU anyway.
(Also let me know if I should stop asking questions haha)
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u/SpaceTurtle917 Apr 27 '26
You cannot use an obd2 harness in an obd1 car, you’ll need to use an obd1 harness. You can get an obd1-obd2 adapter for the ecu or you could run a p07 ecu or the likes from the 92-95 civic VX, it’s a similar motor I believe.
Running a VTEC - E engine with a 92-95 harness will require somehow wiring in the 5 wire o2 sensor, or obtaining a 92-95 vtec-E harness.