The P0271 code indicates that the engine control module has detected an electrical circuit malfunction in the fuel injector for cylinder 4. Specifically, it signifies a 'high' voltage condition, which typically occurs when the circuit is open or cannot be grounded properly.
An internal open circuit or failure within the cylinder 4 injector solenoid prevents the circuit from completing.
Frayed, broken, or burnt wires leading to the injector create an open circuit.
Corrosion or contamination in the injector electrical plug increases resistance or breaks the connection.
The injector signal wire is shorted to a power source, causing the voltage to remain high.
The internal injector driver circuit within the engine computer has failed.
No. While a failed injector is common, the code can be caused by a broken wire or a corroded connector that is easier and cheaper to repair.
P0271 is specifically an electrical circuit code. A mechanical clog or leak may cause a misfire, but it will not trigger this specific high-voltage circuit code.
Only as a last resort. PCM failures for individual injector circuits are rare; double-check all ground connections and harness integrity before replacing the module.