What does it mean?
Fuel injectors have taken the place of carburetors in modern automobiles. Carburetors tend to be difficult to adjust. They cannot deliver the same fuel mixture to each cylinder in a car’s engine, because each cylinder is located different distance from the carburetor. Twin-carburetors represented an improvement, but they are still hard to keep tuned. Fuel injectors deliver the fuel air mixture in precise bursts.
They act like the nozzle of a hose whose flow is controlled by a spring, injecting the fuel into the cylinder as a fine mist. All the cylinders can be served by a single injector, or each by its own injector. A common type fuel injector is a pulsed type, in which times the bursts to coincide with the piston’s stroke. In modern cars and truck, electronics controls the timing; actuating an electromagnet that controls a spring’s action inside the injector body to open and close the outlet.
P0261 tells you where the problem is believed to be located, and what the problem appears to be. In this case, the code tells you it is a powertrain issue, that either the fuel mixture for the #1 cylinder is out of range or the fuel injector’s spray pattern is abnormal, or both.