OBD1 to OBD2 Harness Adapters

[G. Wiffington]

So I originally ordered the entire H22A swap with the M2A4 trans from HMO. When I ordered the swap Steve said he was going to hook me up with an M2B4 just for mentioning I was a CB7Tuner member which I thought was awesome! Well, yesterday he calls me to say his guys got the order mixed up & sent me the whole Euro-R swap instead which is yet again, awesome! But, what caught me off guard was that I was ready for the OBD1 swap.

With this being said, I started researching & saw that most people swap out the OBD2 dizzy, ECU, & injectors to the OBD1 setup. But, when Steve & I were talking yesterday he mentioned that I could just get the ECU jumper harness adapter from Rywire.com so that I can still use the OBD2 ECU. On Rywire I also found jumper harness adapters that allows the OBD1 harness to connect straight to the OBD2 fuel injectors, as well as an adapter harness for the OBD2 Dizzy so it connects to the original OBD1 harness. I believe I also read that to use those injectors you must bypass the resistor box? I have a donor CB to pull the plug for the resistor box to make a bypass pigtail. So do you literally just solder all 5 of the wires together?

Distributor Adapter: http://www.rywire.com/product-p/dis-1-2-10-pin.htm

Injector Adapter: http://www.rywire.com/product-p/inj-adapter-1-2.htm

OBD1-OBD2B Adapter Harness: http://www.rywire.com/obd1-to-obd2b-...obd1-obd2b.htm

The only thing I am not sure about is if the Euro-R's ECU is OBD2"A" or "B" so I can buy the correct harness ECU adapter..can someone shed some light on that subject? Are there specific years for each A & B? I am sort of lost when it comes to the OBD2 stuff. I looked up a PCD ECU on Ebay & it looked like the connectors spot were for a OBD2B.

Also, if that all works out, when wiring up the additional wires for VTEC, would I run the wires to the original engine harness (because it connects to the ECU through the adapter) or do I run the wires straight to the PCD ECU?

[Jarrett]

I think I would strongly reconsider this. You're already talking about $215 worth of adapters to get an untunable ECU installed. On this particular engine, the IACV is also going to give you issues. You OEM harness won't have provisions for a 3-wire IACV and the PCD won't recognize the 2-wire if you were to use an adapter.

So...

I would salvage the knock sensor and VTEC wiring from the Accord Euro-R harness and integrate those into your OEM harness.

Here's your parts list:

2-wire IACV adapter from Rosko Racing
throttle cable bracket from Rosko Racing
Rywire injector adapters (that you linked)
OBD1 external coil distributor from '92-'95 DOHC Prelude
driver's side post mount from '92-'96 DOHC Prelude
'92-'96 Prelude H22A header (this is done regardless of whether or not this is a Euro-R swap or standard H22A swap
OBD1 ECU such as a P28/P72/PO6

This is the best way to get this swap installed. It's a bit more involved than a standard OBD1 H22A installation, but that has more to do with it being a newer engine and not that it's a Euro-R. Aside from the Rosko components, anyway.

[Bunta]

I happen to have the Euro R ECU (got it from Steve with my Euro r Swap, wish he hooked me up with a transmission instead ), is there a visual way to tell between the OBD2a and b? You do just solder the 5 wires right at the plug on the resistor box, I did that and had no problems.

[Bunta]

I would salvage the knock sensor and VTEC wiring from the Accord Euro-R harness and integrate those into your OEM harness.

Here's your parts list:

2-wire IACV adapter from Rosko Racing
throttle cable bracket from Rosko Racing
Rywire injector adapters (that you linked)
OBD1 external coil distributor from '92-'95 DOHC Prelude
driver's side post mount from '92-'96 DOHC Prelude
'92-'96 Prelude H22A header (this is done regardless of whether or not this is a Euro-R swap or standard H22A swap
OBD1 ECU such as a P28/P72/PO6

This is the best way to get this swap installed. It's a bit more involved than a standard OBD1 H22A installation, but that has more to do with it being a newer engine and not that it's a Euro-R. Aside from the Rosko components, anyway.

I didn't use injector adapters or the DS post mount.

[G. Wiffington]

I think I would strongly reconsider this. You're already talking about $215 worth of adapters to get an untunable ECU installed. On this particular engine, the IACV is also going to give you issues. You OEM harness won't have provisions for a 3-wire IACV and the PCD won't recognize the 2-wire if you were to use an adapter.

So...

I would salvage the knock sensor and VTEC wiring from the Accord Euro-R harness and integrate those into your OEM harness.

Here's your parts list:

2-wire IACV adapter from Rosko Racing
throttle cable bracket from Rosko Racing
Rywire injector adapters (that you linked)
OBD1 external coil distributor from '92-'95 DOHC Prelude
driver's side post mount from '92-'96 DOHC Prelude
'92-'96 Prelude H22A header (this is done regardless of whether or not this is a Euro-R swap or standard H22A swap
OBD1 ECU such as a P28/P72/PO6

This is the best way to get this swap installed. It's a bit more involved than a standard OBD1 H22A installation, but that has more to do with it being a newer engine and not that it's a Euro-R. Aside from the Rosko components, anyway.

Yeah, the whole Euro R thing really threw me off.
So I can still use the Euro injectors even with a OBD1 ECU? Would I still have to bypass the resistor box?
With IACV adapter, the site said I need to get a USDM IACV, correct?
But, without involving the cost of all the adapters I listed, would that process actually work?

[G. Wiffington]

I happen to have the Euro R ECU (got it from Steve with my Euro r Swap, wish he hooked me up with a transmission instead ), is there a visual way to tell between the OBD2a and b? You do just solder the 5 wires right at the plug on the resistor box, I did that and had no problems.

Well, I went to the SWAP FAQs & I looked at the way the connectors are for the B version. looks like on the B version ECU connectors for the "D" location is not present. On the A version "B" location is left blank on the ECU. (From what I saw, not sure if that is 100%)

[Rilas]

A few things to consider. Jarrett pretty much has everything correct. Although trying to find a decently priced OBD I DOHC distributor isn't very easy anymore. I just made a jumper harness myself between my OBD I harness and my OBD II DOHC distributor that came on my F22B DOHC. If you do some checking around, in the early years of the OBD II switch over Honda didn't even change the colors of the wires for the OBD II stuff. I just picked up a pigtail for it off a 96-97 Accord, plenty of them in junkyard these days.

Yes with the IACV adapter your going to have to buy a OBD I IACV, sadly these aren't the cheapest even on eBay. If you were lucky enough to find one in the junkyard your golden. I had to pay $80 for mine on eBay.

[G. Wiffington]

A few things to consider. Jarrett pretty much has everything correct. Although trying to find a decently priced OBD I DOHC distributor isn't very easy anymore. I just made a jumper harness myself between my OBD I harness and my OBD II DOHC distributor that came on my F22B DOHC. If you do some checking around, in the early years of the OBD II switch over Honda didn't even change the colors of the wires for the OBD II stuff. I just picked up a pigtail for it off a 96-97 Accord, plenty of them in junkyard these days.

Yes with the IACV adapter your going to have to buy a OBD I IACV, sadly these aren't the cheapest even on eBay. If you were lucky enough to find one in the junkyard your golden. I had to pay $80 for mine on eBay.

Well that is where I got that idea from, you lol. I saw the little harness adapter you made which is exactly like the one I put in the link from Rywire.

I just want to know if the process I described in my first post would work. I know it is pricey but it just makes sense with the way everything would hook up. Because that is basically what Steve from HMO suggested. I am no mechanic but I just try to do research enough to make sense.

Yeah this Euro R thing really threw me a curve ball lol.

[Bunta]

Well, I went to the SWAP FAQs & I looked at the way the connectors are for the B version. looks like on the B version ECU connectors for the "D" location is not present. On the A version "B" location is left blank on the ECU. (From what I saw, not sure if that is 100%)

Well I'm looking at my (jdm "square") ecu and spot "D" is blank.

[Jarrett]

I didn't use injector adapters or the DS post mount.

What engine harness did you use? The OEM harness from your Accord, or did you adapt the OBD2 Euro-R harness?

And what does your post mount look like?

The first picture is of an Accord Euro-R engine mount bracket commonly referred to as the post mount. You can see that the spacings for the vertical stud and bolt are fairly narrow compared to the two mounts pictured below it.



The next picture is a '90-'93 Accord post mount on an F23A block with an H23A1 head. Just focus on the spacing of the vertical studs and ignore the rest of that. So, you see that the portion of the rubber driver's side mount for a CB7 will need a post mount that matches its stud spacing. The Euro-R above is too narrow.



Below is the post mount from a '92-'01 Prelude (11910-P13-000) with either the H23A1 or the H22A1 (same block casting, so same mount bracket). You can see it also has vertical studs that are spread out, similar to the F22A bracket in the '90-'93 Accord.



So which one is your engine using? Do you have any pictures of fitment?

Yeah, the whole Euro R thing really threw me off.
So I can still use the Euro injectors even with a OBD1 ECU? Would I still have to bypass the resistor box?
With IACV adapter, the site said I need to get a USDM IACV, correct?
But, without involving the cost of all the adapters I listed, would that process actually work?

Try not to think of the injectors as being an ECU-related variable. Injectors are either low-impedence or high-impedence. The easiest way to think of it is to know that "impedence" is a synonym for resistance. So, if you have low-resistance injectors, they need a resistor box to create the resistance within the circuit. If you're running high-resistance injectors, then no additional resistor is needed. My description shouldn't be used to understand what's going on electrically within the circuit, as I may have worded something wrong, but understand that what I said in terms of compatibility is true.

So, yes, if you are using high-impedence OBD2-style injectors you will need to delete the resistor box with the method you mentioned previously.

A USDM or JDM IACV doesn't matter as long as it is 2-wire. And no, it will not work with an OBD2 ECU, which was my point. I suppose you could try to use the 3-wire ECU that's on the Euro-R manifold if you're going to use the Euro-R harness and ECU, but I'm not going to be able to offer much help there.

[Bunta]

If I remember correctly I swapped the plugs off the Euro R harness and soldered them. As far as the post mount I was confused, I remember trying it and the mount not lining up so I had to pull the one off the stock engine.


* and for the OP, You do not even need the plugs in place for the wiring that connects to the resistor box, you can cut both plugs off (save them, they could be useful in the future) and just solder all the wires together and then seal it up ( heat shrink tubing, GOOD electrical tape or maybe even the liquid electrical tape stuff.

[G. Wiffington]

If I remember correctly I swapped the plugs off the Euro R harness and soldered them. As far as the post mount I was confused, I remember trying it and the mount not lining up so I had to pull the one off the stock engine.


* and for the OP, You do not even need the plugs in place for the wiring that connects to the resistor box, you can cut both plugs off (save them, they could be useful in the future) and just solder all the wires together and then seal it up ( heat shrink tubing, GOOD electrical tape or maybe even the liquid electrical tape stuff.

Good idea. I just didn't want to cut up my car's harness. My buddy has a CB that he trashed which is sitting in his grandfathers junkyard/backyard/hoarding random stuff lol. He lets me pull parts off of it so I might use that resistor connector & solder those wire together.

[G. Wiffington]

To Jarrett: It looks like the Prelude mounting post has a different part number compared to the CB7 bracket. Is there a difference between the two? Looks like the picture with the F22 bracket on the F23 block has the left side mounting hole missing on the actual block.

Can I use my original F22 bracket?

[Jarrett]

People have used the F22 bracket, and it supposedly creates the correct angle for the rubber mount to bolt to when installed, but one of the bolts to secure it to the block won't line up. The correct part is the P13 mount from any DOHC '92-'01 Prelude.

[Jarrett]

I didn't use injector adapters or the DS post mount.

If I remember correctly I swapped the plugs off the Euro R harness and soldered them. As far as the post mount I was confused, I remember trying it and the mount not lining up so I had to pull the one off the stock engine.

Well then that's why you didn't need adapters. Sure what you did worked, but you'll have a hard time finding a harness builder recommending soldering wires together when it comes to fuel injection or spark-related wires. Actually, yo'll have a hard time getting to recommend it for anything over crimping.