Cylinder 3 Glow Plug Circuit
The P0673 code means the vehicle's onboard diagnostic system has detected: Cylinder 3 Glow Plug Circuit. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $50 - $500 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Cylinder 3 glow plug not heating
- Reduced system performance
- Warning indicators on dashboard
Probable Causes (Ranked by Likelihood)
- Failed glow plug in Cylinder 3 Very High
- Wiring damage or corrosion in the circuit High
- Poor electrical connection at module or component Moderate
- ECM or control module internal failure Low
Step-by-Step Diagnostic Procedure
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Use a scan tool to read data related to Cylinder 3 Glow Plug
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Inspect all related wiring, connectors, and grounds for damage, corrosion, or loose connections
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Measure circuit voltage, resistance, and continuity to identify the fault type
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Check for technical service bulletins related to this code for your specific vehicle
Common Fixes by Vehicle
What techs usually find when diagnosing P0673 on specific vehicles — tap your vehicle for the fix and the exact part:
2001-2010 Duramax LB7/LLY/LBZ/LMM hard DIY
P0673 = Glow Plug #3 (driver-side middle). On Duramax, the glow plugs sit under the valve cover studs and require patience to access. Remove the valve cover to inspect for oil-soaked glow plug harness -- if a valve cover gasket is leaking, the harness fails and sets multiple glow plug codes. Replace both the gasket and harness if oil contamination is visible.
Labor: 4-5 hours (all 8 + valve cover gasket)2003-2007 Ford 6.0L Power Stroke hard DIY
6.0L P0673 = glow plug #3. Valve cover gaskets leak oil onto the harness on 6.0L Fords. If P0673 returns after replacement, pull the valve cover and inspect the glow plug harness -- Ford p/n 4C2Z-12A690-EA is the updated harness. Replace both the gasket and the harness to prevent recurring faults.
Labor: 5-7 hours (all 8 + VCG + harness)2008-2010 Ford 6.4L Power Stroke hard DIY
6.4L P0673. Cab-off labor saves time on 6.4L glow plugs. Replace all 8 with Motorcraft ZD-13. Check the GPCM for proper operation before installing new plugs -- a failing GPCM will burn up new plugs in weeks.
Labor: 6-10 hoursFrequently Asked Questions
What happens when Cylinder 3 glow plug fails?
A single failed glow plug in Cylinder 3 may cause hard starting in cold weather and rough running until the engine warms up. In mild temperatures, you may not notice any symptoms. Multiple failed glow plugs cause progressively worse cold starting.
How much does a glow plug replacement cost?
Individual glow plugs cost $15 to $50 each. Labor is the main expense as some glow plugs are difficult to access. A single glow plug replacement typically costs $100 to $300. Many shops recommend replacing all glow plugs at once.
Can a glow plug break off during removal?
Yes, especially on high-mileage diesel engines. Carbon buildup and corrosion can seize the glow plug in the cylinder head. Special extraction tools exist for broken glow plugs. Applying penetrating oil days before removal helps.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0673 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
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