Hey all! First post here, be nice. 🤣

Vehicle is a 1994 4th gen Honda prelude with a H23a1 engine, OBD1 ausdm. Engine (h22z1) is from a 1999 5th gen honda prelude OBD2A ausdm.

So for a little context before I display my problem… I own an AUSDM 94 honda prelude (OBD1 H23A1), it recently blew its engine, so I brought a H22Z1 out of a 99 plate 5th gen prelude (OBD2A) and got the ecu from a 97 plate 5th gen H22A4 (Also OBD2A).

The issue I’ve come across is that from 97 onwards, all prelude ecus have a built in immobiliser that is wired into the body loom. Seeing as how I’m still using my 4th gen body loom, I don’t have the bits necessary, nor do I have the patience to wire it up into my loom if I don’t absolutely have to find the stuff and wire it in…

My questions are…

  1. Is there a way to trick the ecu into thinking it has the transponder signal even though it doesn’t have the signal?

  2. Is there a reliable way to remove the circuit inside the ecu? I have a soldering iron and such. Could I remove it myself safely? If so what do I need to put in its place?

  3. If I do need to wire in all the components for the immobiliser, can I use aftermarket stuff (for example, a keyless remote with a transponder and reciever to turn the car into push button start or even just to get it to turn the ecu on so i can turn key start it… would an aftermarket antenna and memory drive to store the key codes/frequencies work, Or does it need to be the factory stuff only?

  4. If question 3 is viable, is there a way for me to automate the steering lock with the push button start. Think the new car keyless systems, where the key doesnt have to be in a specific spot, just inside the car. Push for ignition, again for on. Could I use the electrical signal from the car going into ignition from the push button, and use that electrical signal to unlock the steering lock?

My thought process from question 3 is that I can possibly facilitate the retrieval of the factory antenna and reciever (if it’s not in the ignition barrel), and possibly make it work by wiring the stuff in, but that’s a long, dangerous and tedious process, with a lot that could go wrong.

I know this was a lengthy post, so far the car runs and drives on the obd1 ecu, it’s just down on power, and it’s missing on partial throttle, so I don’t need this to drive the thing, I just want to know if there is an alternative to buying a 2 grand ecu to manually tune the thing if I don’t actually need to.

Thanks all. Hopefully you all can point me to victory. 😅😆