P0673 on the 6.0L Power Stroke is a glow plug cylinder 3 circuit fault. The 6.0L glow plug control module monitors each plug's circuit while preheating the cylinders for cold starts. P0673 sets when the module detects the cylinder 3 glow plug circuit outside its expected range, meaning an open plug, a shorted plug, or a break or short in the wiring to cylinder 3.
Like the other per-cylinder glow plug codes on the 6.0L, P0673 narrows the search to one plug and its feed. The glow plugs sit under the valve covers and are fed through the valve cover harness, an area exposed to oil and heat. A single-cylinder code most often means a failed cylinder 3 plug or a damaged harness connection, so checking the plug's resistance and its wiring resolves the code efficiently.
What P0673 means
The glow plug control module energizes each plug and monitors current draw. P0673 sets when the cylinder 3 circuit is outside the acceptable range, indicating an open glow plug, a shorted plug, or an open or short in the wiring feeding cylinder 3. It isolates the fault to the cylinder 3 plug and its circuit.
Common causes
- Open or burned-out cylinder 3 glow plug
- Damaged valve cover harness feeding cylinder 3
- Corroded or loose glow plug connector
- Shorted glow plug drawing excess current
- Wiring open or shorted to cylinder 3
Symptoms
- Hard cold starting and extended cranking
- White smoke and rough running when cold
- Check engine light with P0673 stored
- One cylinder slow to fire on a cold morning
- Little change once the engine is warm
How to diagnose it
Access the cylinder 3 glow plug and measure its resistance; a good plug reads low, an open plug reads very high. Inspect the valve cover harness and glow plug connector for oil, corrosion, and damage. Check the wiring from the glow plug control module to cylinder 3 for an open or a short. Compare cylinder 3 to a known-good cylinder to verify the fault is isolated rather than affecting several plugs, which would point at the module or a shared feed.
How to fix it
Replace the cylinder 3 glow plug if it tests open or shorted, and repair or replace a damaged valve cover harness or corroded connector. If the plug and wiring are good but the fault persists, test the glow plug control module. After the repair, clear the code, confirm all glow plug circuits pass, and verify a clean cold start. For glow plugs, valve cover harnesses, and control modules for your 6.0L Power Stroke, contact sales@coredieselparts.com.
Frequently asked questions
Is P0673 an emergency?
No, but cold starts will suffer. One dead glow plug means harder starting, white smoke, and rough running until warm. Repair it before cold weather to avoid a no-start.
Could the valve cover harness be the cause?
Yes. On the 6.0L the glow plug feed runs through the valve cover harness, which oil and heat degrade. A single-cylinder code often traces to that harness rather than the plug.
Do I need to replace the glow plug controller?
Not usually for a single-cylinder code. Start with the cylinder 3 plug and wiring; the controller is more likely at fault when multiple circuits fail at once.
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