P0674
Cylinder 4 Glow Plug Circuit/Open
Glow plugs (diesel)
Generic OBD-II
High
What it means
P0674 means the engine computer has detected an open (broken) circuit for the cylinder 4 glow plug on a diesel engine. Glow plugs preheat the combustion chamber for cold starting, so a dead plug or broken wire on cylinder 4 typically causes hard cold starts, rough running until the engine warms, and white exhaust smoke.
High
Can I keep driving? Usually driveable in mild weather, but expect hard cold starts and rough cold-running until the glow plug circuit is repaired.
Common symptoms
What you'll notice
- Hard starting, especially in cold weather
- Rough running or a stumble right after a cold start
- White or blue exhaust smoke on a cold start
- Check-engine light (and often the wait-to-start/glow-plug light) on
Common causes
Most likely first
- Failed cylinder 4 glow plug (open element)Likely
- Open or broken wiring in the cylinder 4 glow plug circuitCommon
- Corroded or loose connector at the glow plug or glow-plug control moduleCommon
- Faulty glow plug control moduleLess often
- Faulty ECM (least likely)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the fault is on cylinder 4 specifically.
- Measure the cylinder 4 glow plug resistance and replace it if the element is open.
- Inspect the glow plug wiring and connector for breaks, corrosion, and loose pins.
- Check the glow-plug control module outputs and its connections.
- Clear the code and retest with a cold start; if it returns, evaluate the control module and ECM.
FAQ
Quick answers
Is it safe to drive with P0674?+
In mild weather usually yes, but cold starts will be hard and the engine may run rough until warm. Fix it before cold weather to avoid a no-start.
Can I just clear P0674?+
You can, but an open glow plug circuit will set the code again until the plug or wiring is repaired.
Related codes
Often seen with P0674
Read & clear P0674 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX