When checking the electronic fuel injection system, proceed as follows:
Check the security of the electrical connectors. A broken electrical connection in the connector leads to malfunctions in the electronic fuel injection system.
Check the condition and state of charge of the battery, because the engine control unit (PCM) and sensors may not work properly when the supply voltage is low.
Check the condition of the air filter element. When it is contaminated, the amount of air entering the engine cylinders is reduced, as a result of which the engine power will decrease and fuel consumption will increase.
Check the operation of the fuel pump. If the fuel pump is not working, check the fuse in the fuel pump power circuit. If the fuse is good and the fuel pump is not working, check the fuel pump power circuit.
Check the vacuum hoses connected to the intake manifold for damage, defects and loose connections.
Remove the air intake duct from the throttle body and check the inside of the throttle body for soot deposits and other debris, especially around the throttle body. If contaminated, check the forced crankcase ventilation systems (PCV) and exhaust gas recirculation (EGR).
When the engine is running with a stethoscope, alternately attached to each nozzle, check their performance. If clicks are heard, the injector control circuits are good, but be aware that internal contaminants can interfere with the operation of the injectors. In this case, clean or replace the nozzles.
If the clicks emitted during the operation of the nozzle are not audible, disconnect the electrical connector and measure the resistance of the nozzle. If the injector resistance is out of specification, replace it.
If the injector does not work, but its resistance is within the normal range, check the engine control unit (PCM) and electrical power supply circuit of the injector.