The fuel injector delivers the air/fuel mixture in specific amounts. All the cylinders can be supplied by a single injector or each cylinder can have one injector.
Commonly, injectors are of the pulsed type, those whose bursts coincide with the stroke of the piston. To control the timing, an electromagnet is activated which in turn controls the action inside the injector body to open and close the outlet.
When the P0261 OBDII fault code is set, it is because the vehicle’s computer has discovered that the air/fuel mixture in cylinder number 1 is out of spray pattern.