GU engine light code 77

Hi. I recently bought a auto 2005 patrol zd30 . Owned it 3 days then lost all power when cold. Put foot down and it would idle away for about 10 mts then take off.. When warmed up it was good.
It then started throwing engine light and go into limp mode.
I sent it to a shop that said pump. Sent it to a second shop that said gearbox.
Sent it to a diesel specialist, 5 days later after changing, crank angle sensor and balancer,
Airflow metre,flyby wire,throttle sensor, then fitted new fuel pump and injectors, I got it back drove it home, idled in my driveway for a few mins then the engine light came on. Took it back, code 77, pump timing, they fitted a second new pump, and did the same thing. After fitting 3rd new pump and checking pump timing was set right and checking all my drive gears for wear, perfect. Picked it up drove it the next morning and,yep engine light, same code 77.
They have told me there is nothing else they can do or fit to that engine to stop it.

Please if anyone has a idea of what it can be, or might be.
Have exhausted every avenue. Looked for holes cracks in pipes,bad wiring, corrosion.

Hope someone has a idea. Barry.

have u taken it to Nissan?