Certain Honda engine swaps require changes to the alternator connector.
In most cases, wire color matching does the job of figuring this out, but sometimes the wire colors are completely different. Â
OBD0 and OBD1 B/D-series engines and wiring use the same 4-wire round alternator plug, so they are compatible with each other ie. plug n’ play.
OBD2 B/D-series alternators on the other hand use a 4-wire  rounded square plug and are compatible with OBD2 vehicles but are not backwards compatible to OBD0/1 wiring.Â
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So, when using an OBD2 alternator (for whatever reasons) in an OBD0/1 vehicle, adaptation of the OBD2 alternator plug needs to be made to the OBD0/1 engine wire harness.
Here are common scenerios when trying to adapt older or newer alternators due to differences in OBD types :
OBD-1 to OBD-0 alternator connector
This scenerio happens when using an OBD1 engine in an OBD0 vehicle or vice versa.
As mentioned already, OBD0 and OBD1 alternators share the same round style alternator plug.  Making this type of scenerio PnP or plug n’ play. No need to change the alternator plug here. However, for some reason the plugs differ, simply color match the  wires and adapt the OBD-1 alt plug to the OBD-0 wire harness.
JDM OBD0 and OBD1 alternators use the same round style plug but only use 3-wires. Don’t let the missing 4th wire fool you. You can still use the JDM alternator with your 4-wire alt. plug.
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OBD-2 to OBD-0 alternator connector
This scenerio happens when using an OBD2 engine in an OBD-0 vehicle.
When adapting an OBD2 alternator to an OBD-0 engine harness follow this wire color chart:
| OBD0 (DPFi – STD/DX)Â | Â Â — Â | OBD2 plug |
|  yellow |  to | white/red |
| white/yellow |  to | white/green |
|  black/yellow |  to | black/yellow |
|  white/blue | to | white/blue |
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| OBD0 (MPFi – HF/Si)Â | Â Â —Â Â | OBD2 plug |
| blue | to | white/green |
| black | to | white/yellow |
| white/blue | to | white/blue |
|  white/yellow |  to | white/red |
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OBD-1 to OBD2 / OBD2 to OBD-1 alternator
This scenerio happens when using an OBD1 engine in an OBD2 vehicle and vice versa.
When adapting an OBD2 alternator plug to OBD1 engine harness and vice versa follow this chart:
| OBD1Â | Â Â —Â Â | OBD2 plug |
| blue | to | white/red |
| black/yellow | to | black/yellow |
| white/blue | to | white/blue |
|  white/yellow |  to | white/green |
hello 🙂 i have a alternator with 2 wire plug and i want to use wire harness from OBD 1(4 wire plug) so what can i do ?
Best regards
daniel,
I would run the two other alternator wires to complete the connection for the 4-wire OBD1 alternator plug. I believe I replied back to you via email.
I have a 92 GS-R Teg with a Type r motor. My alternator plug is green and round with only three wires. I found out that my harness is hacked up using a JDM harness with usdm plugs from the original gsr harness and the usdm type r harness. Will a usdm alternator work without that fourth wire or do I absolutely need a jdm alternator? Thanks in advance for any help you can provide to me.
David,
From what I recall, yes loosing the 4th alt. wire will still allow the alternator to work and function properly.
My friends JDM OBD1 H22a prelude has 3 pinout on the alternator side..And there are 4 wires at engine harness.I think that the cars old owner made some custom wiring. But alternator is not working properly.. Can i have a wiring diagram ?
I have a crx but its wiring harness shows the same colors as an obd1 harness, its has blue, black/yellow, blue/white, and white/yellow wires, should i wire it the same as the obd1-obd2 diagram? i need to convert to obd2, im definately stumped, any help would be appreciated, thanks
Javan- OBD0 & OBD1 alternators are cross compatible. The OBD1 alternator should plug n play to your OBD0 alt. plug no problem. If the wire colors match up too, its that much easier.