Northbird Nominated

My camry ecu
Mechanic said it's faulty because car could not start

Guys I worked on the engine of my camry 2003 afterwards, the vehicle started but went off after about 30mins and keeps going on and off.

Before now, the mpg has been poor and stalls a lot.
So these electricians were brought to check fuel pump and there were no issues, the second person came and after checking all 'checkables' said it was the brainbox. I still can't figure how he arrived at that conclusion since he wasn't using any car scanner.

Now the car I no longer starting. What could be the issue and how can it be resolved without changing brain box which I understand is a bit tricky and requires coding.
I'm in Awka and I don't know very good auto mechanics and I don't want my car to be 'Kazeemized'

I need solutions abeg.
Cc: Gazzuz
Radautoworks
Sienna
Ikenna
AutoElectNg