ECU/TCM replacement advice?

Mazda Bongo Friendee SGL5 / 4WD/AT
Most cold starts the following happens:
• Fans running
• No glow plug light
• No aircon
• Limp mode

Occasionally it will start normally but will overheat.

We suspect the TCM is faulty as per https://www.2carpros.com/questions/possible-ecu however since it does work sometimes, could it be the wiring instead?

Getting a replacement part shipped to Australia is expensive, especially if it is not the root cause.

Thanks.