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.
P0279 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 #7 cylinder is out of range or the fuel injector’s spray pattern is abnormal, or both.
Note: Circuit Low Input codes are often the result of low battery voltages (that can have many possible causes), bad connections across electrical connectors or previously repaired wiring, as well as corrosion in electrical connectors.
Other possible causes of low input voltages include poor installation of aftermarket components, poor quality aftermarket components like fuses, relays, and switches, and modification of the electrical system that could include the use of conductors that are not rated for use in a particular application. However, poor connections often result in high resistances in some parts of the circuit, which is why it is important to perform resistance and continuity checks during the diagnostic procedure.