scoubix

Roverlike wrote:

EKA do exist on cars with infrared fobs. I have it. Maybe not with all of them, and not all models, but it is there. I do not know if early 200/400 would have EKA implemented, but I would expect it is implemented starting 1994 forward.

EKA does exist on 'some' cars with infrared, but not the 200/400 R8 generation, that's for sure. They only implemented EKA when RF fobs and 5AS was introduced for MY 94.5.
Cars that have EKA with infrared are the Rover 600 and 800, 800 only starting from VIN 194916. That is when they started pairing the CCU with the engine ECU (only with MEMS, not PGM-FI cars). Cars prior to that VIN don't have EKA (I own a 800 with VIN below that number and it doesn't have EKA at all). From VIN 230967 (96 MY), they moved to RF fobs as well.
Rover 600 had EKA from VIN 144845. When they moved to RF starting from VIN 246797, they removed the need for EKA : a transponder was inside the key itself.

Passive immobilisation is extension of EKA code to further securtiy measure. To stop the car being started if the car was even unlocked by the fob, but left open and unattended. Without the fob you will not be able to start it. Honda engined cars can have passive immobilisation implemented in the same way EKA code is implemented.

Still, I don't see technically how this can relate to ECU pairing between the 5AS and the engine ECU, which you implied was mandatory for passive immobilisation. The Honda PGM-FI has never been technically capable of being paired with the 5AS. So if passive immobilisation was available on those cars, it would mean it's just a timer that starts when you stop the engine and triggers immobilisation after 30 seconds, instead of just waiting for a fob signal.

I'll send you a PM for further discussion