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Immobiliser & ECU Help?


New member

I am building a Haynes Roadster and using a 2005 NBFL MX5 1.8 vvt for the engine and running gear.

As my car is a fairly basic in terms of electrics I decided to develop a bespoke wiring loom rather than use the entire Mazda loom and all its various looms for electric seats, windows etc etc which are not required on my car.

However, we are having real problems now trying to reverse engineer the Mazda engine loom to simplify the loom down, the immobiliser and links to the ECU are causing real problems.

For seemingly obvious reasons Mazda have made this very complicated and difficult to defeat, but with me trying to do it for genuine reasons it makes it a nightmare to try and understand...

Therefore i was wondering whether anyone had detailed information or data (or any tips for that matter) on the interactions between the immobiliser system and the ECU to allow us to finish of the custom wiring loom?

Any help, diagrams, data, links would be most appreciated as this is starting to become a real issue with the build now.

Thanks for reading.


New member
Hi there,
I have just come across your post from last year :) I am going through the exact same issues that you had, in that I am building a Haynes Clubbie with a 98 NB 1.8 motor and gear box.
Did you find anything out there that solved your problem? if so can you please point me to where I can grab a copy or the links etc. that will remove the pile of spaghetti off my shed floor :)

Look forward to hearing back from you.