Check Engine Problems 2L-Te

Hi, my engine lights keeps comming on everytime i hit an uphill and press gas down. if i slowly accelerate it wont come on but if i press gas down and shifts up in 4th and 5th than the light come back on. The ecu is givving to fault codes and not even on diagnostic computer it still gives no errors but the engine light keeps comming on when on full throttle. Can anyone help me please?

Hilux Ln112 (1995 model)
2L-Te Turbo Diesel Automatic

Kevin Zammit
MALTA