P0671

Code P0671 indicates a malfunction within the glow plug circuit for cylinder number one on diesel engines equipped with an emissions reduction system. This specific fault code signals that the Engine Control Module has detected either an open or shorted condition in the electrical path supplying power to the first cylinder's pre-heater element. While this issue is frequently associated with failed heating elements, corroded connectors, or blown fuses within the glow plug relay bank, it can also stem from internal wiring harness damage near high-heat zones. A professional technician should verify circuit continuity and resistance against official service specifications before condemning components. Inspection must include checking for voltage supply at the connector to isolate whether the fault lies with the actuator itself or the control module's output stage.