P0671: Cylinder 1 Glow Plug Circuit — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
The definition identifies an electrical condition in the cylinder 1 glow-plug circuit. It establishes the monitored circuit, but it does not by itself identify whether the component, connector, wiring, power supply, ground, control command or module input is responsible; circuit layout and diagnostic thresholds are vehicle-specific.
Affected system: Glow-plug control
Symptoms
- Cold starting a diesel engine may be harder when cylinder 1 has a glow-plug circuit fault.
- A glow-plug or engine warning lamp may be displayed.
Possible causes
- The cylinder 1 glow plug may have a damaged heating element.
- Broken wiring, oxidized connectors or a glow-plug controller fault may interrupt its circuit.
What to check
- Confirm cylinder 1 numbering and check for related preheating codes.
- Inspect the cylinder 1 connector and wiring with the engine cool.
- Check glow-plug resistance and circuit supply against the manufacturer's specifications before replacing parts.
Also written as: P0671-00, P067100, PO671 (some scan tools add the fault-type byte, e.g. -00).