OBD-I to OBD-II

'92 Si VTEC · Post by **jjmartin349571** » Tue Mar 10, 2015 9:40 am

Hi folks,

Last night Laura asked me what I need to do to my 6g Accord to get it running, quickest method possible. I was meant to be collecting an OBD-II engine but me and the chap who was selling it kept missing each other and he is now up in Norfolk, although I'm still welcome to travel up and collect

I've already got an H22A in situ, but it's from an OBD-I car whereas my car is OBD-II... I'm thinking that the path of least resistance is swapping the relevant bits over to make it OBD-II compatible, but my question is what to I need to do in order to achieve this??

I'm open to alternative ideas however - I have thought of running OBD-I by buying an adapter harness and cutting it up so that I can convert the two OBD-II plugs for the interior looms to OBD-I, and plug the engine loom direct in to the ECU but I'm not sure that would work??

All advice appreciated

Cheers,
Josh

Post by **NafemanNathan** » Tue Mar 10, 2015 9:50 am

So just to clarify, you want to use the ODB1 Engine and ECU with an OBD2 harness?...

'92 Si VTEC · Post by **jjmartin349571** » Tue Mar 10, 2015 10:10 am

Yeah sorry I probably didn't word it very well

to clarify I have an OBD-II car, the interior looms will have to stay OBD-II regardless as I'm not swapping them out
The engine has an OBD-I loom/injectors and what not.
I have an immobiliser free JDM OBD-II H22A Prelude ECU, and I also have a spare OBD-I JDM H22A Prelude ECU

My thoughts are that the easiest method of getting the car running is to bring the engine into line for OBD-II, but any other solutions for getting some combination of the above to work is welcome.

Post by **NafemanNathan** » Tue Mar 10, 2015 10:23 am

Your easiest option is just to get the ODB2>ODB1 ECU Adapter and just plug in the ODB1 ECU. You'll need to plumb in the Injector resistor box and either splice in the connectors for the ODB1 dizzy and alternator, or just run these items from an ODB2 lude.

If you want to run the ODB2 ECU, then you'll still need to either splice in the connectors for the ODB1 dizzy and alternator, or run those items from an ODB2 lude, but rather than splicing in the injector resistor box you'll have to swap in saturated injectors.

The advantage of going ODB1 is for chipping/remapping in the future.

I forget the deal with the knock sensor. Is it a case you'll need to run a new wire to the knock sensor if you run the ODB1 ECU?

'92 Si VTEC · Post by **jjmartin349571** » Tue Mar 10, 2015 11:49 am

The only doubt I had with using an obd1 to obd2 adapter is that I have obd1 wiring coming off the engine, and so that wouldn't be able to go in to the adapter... I was thinking maybe I could saw the engine plug off of the adapter and plug the engine loom directly into the ECU, and the car's interior looms plugged into the 2 remaining sockets of the adapter and then the adapter into the ECU...

Were some H22A engines provided without knock sensors btw?? I thought they all had them. If I'm going obd1 I need the engine bay to ECU loom section anyway so that should be wired appropriately (in theory

).

I didn't think of the tuning aspect RE obd1, that's definitely an incentive as my spare ECU is socketed

mercutio · Post by **mercutio** » Tue Mar 10, 2015 5:48 pm

if the engine is jdm it will come with a knock sensor, If you swap over the inlet manifold and wiring and ancillaries from the obd2 engine onto the obd1 it should be plug and play