P0674: Cylinder 4 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 4 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
- The diesel engine may take longer to start in cold weather if the glow-plug circuit for cylinder 4 is not working.
- An engine or preheat warning indication may appear.
Possible causes
- The glow plug for cylinder 4 may have a failed heating element.
- Damaged wiring, loose or corroded contacts, or the glow-plug control module may be responsible.
What to check
- Identify cylinder 4 correctly and read related fault codes.
- When cool, inspect the glow-plug wiring and connector for cylinder 4.
- Test glow-plug resistance and the feed circuit against the engine specifications before replacement.
Also written as: P0674-00, P067400, PO674 (some scan tools add the fault-type byte, e.g. -00).