If you have windows and mirrors working in both of the front doors, then there isn't a communication problem between the BECM and the outstations or the centre console switchpack, as they all communicate on a serial link to/from the BECM.
The central locking for the front doors are controlled by the outstation, via the serial link from the BECM, so if this is working for the windows/mirrors, then that isn't your problem.
It sounds like the BECM has gone into lockout mode - whether you can still get it open with the EKA or not will depend on if it's in a complete alarm lockout or just an EKA lockout.
If you have KEYCODE LOCKOUT on the dash then leave it alone with the battery connected until it disappears from the dash. Then you can try putting the EKA in. Note that the early ones DON'T require 4x turns to lock to begin putting the EKA in, like the later ones. I think the drivers door just needs to be locked, and then you start by turning to unlock for the number of turns of the first digit. If it doesn't work, and you know that the microswitches in the latch are all functioning as they should, then chances are it has gone into an alarm lockout, which as you have found needs the Faultmate MSV with BECM CPU module to reset the alarm lockout.
I have the equipment to connect to the BECM and reset the alarm lockout. All of the details are on my website - I try to do it for a reasonable price, as I do P38 work as a hooby outside of my normal job. That being said, I am about this week if you need it looked at, but start getting busy and away with work again next week - and then I'm off until the end of December, so won't be doing much P38 wise except on forums until I get back!
Hope this helps,
EDIT: PS - the passenger door and rear doors won't unlock on the central locking until it's out of the lockout situation (whether it need the EKA entered, or hooked up on the bench). Once it's back in a happy place then the rear doors should automatically unlock from their superlocked state, and the passenger door will start working on the central locking again. If the passenger door still doesn't unlock/lock on the central locking once whatever lockout the BECM is currently in, then chances are the Central Locking Motor in the passenger door latch has failed and not activating to lock/unlock the door.
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