What is the reason for the sudden special fuel consumption of the trouble-free light of Omar refrigerated truck?

In the first case, after cleaning the throttle valve, it does not match the engine control unit or the matching is unsuccessful.

In the second case, the engine electronic control system fails, resulting in a rich mixture, how to increase fuel consumption.

In the third case, the engine ignition coil or spark plug is damaged, and the fuel nozzle leaks oil, which leads to an increase in fuel consumption.

In the fourth case, the engine cooling system fails, resulting in the engine temperature being too low and always in a warm-up state.

In the fifth case, the engine has too much carbon deposit, resulting in insufficient combustion.

In the sixth case, the fuel tank ventilation system fails, resulting in fuel vapor leakage.

These are just six common reasons, and there are many situations that will lead to a sudden increase in fuel consumption, so I won't list them here.