Check that electrical connectors are securely connected. A faulty electrical connection in the connector will cause the electronic fuel injection system to malfunction.
Check the battery condition and charge level because the engine control module (PCM) and sensors cannot operate properly with low supply voltage.
Check the condition of the air filter element. When it becomes contaminated, the amount of air entering the engine cylinders decreases, resulting in reduced engine power and increased fuel consumption.
Check the operation of the fuel pump. If the fuel pump does not work, check the fuse in the fuel pump power circuit for a faulty fuse. If the fuse is good and the fuel pump does not operate, check the fuel pump power circuit.
Check the vacuum hoses connected to the intake manifold for damage, defects, or poor connection.
Remove the air intake pipe from the throttle body and inspect the inside of the throttle body for soot deposits and other contaminants, especially around the throttle plate. If contamination is present, check the positive crankcase ventilation (PCV) and exhaust gas recirculation (EGR) systems.
[The information was taken from a web portal toyotaman.ru]
While the engine is running, use a stethoscope placed in turn on each injector to check their functionality. If you hear clicking sounds, the injector control circuits are working properly, but keep in mind that internal contaminants can interfere with the operation of the injectors. In this case, clean or replace the injectors.
If the clicking sounds produced by the injector are not heard, disconnect the electrical connector and measure the resistance of the injector. If the injector resistance differs from the required value, replace it.
If the injector does not work, but its resistance is within the normal range, check the engine control module (PCM) and the electrical power circuit of the injector.