What Does P0681 Mean?
The PCM has detected a malfunction in the glow plug circuit for cylinder 11. This applies to large-displacement diesel engines with 11 or more cylinders. The glow plug for this cylinder is not functioning correctly, which affects cold-start combustion in that cylinder. The driver may notice extended cranking, rough idle when cold, and white exhaust smoke during startup.
Common Causes
40%
Failed cylinder 11 glow plug (open or shorted)
25%
Open or shorted wiring in the harness to cylinder 11
20%
Glow plug control module output fault for cylinder 11
10%
Corroded or damaged connector at cylinder 11
5%
Ground circuit resistance issue for the affected bank
Diagnostic Steps
1
Measure cylinder 11 glow plug resistance and compare to manufacturer spec (typically 0.3-1.5 ohms for heavy-duty diesel); OL or near-zero readings indicate failure.
2
Verify voltage at the cylinder 11 glow plug connector during GPCM activation; battery voltage should be present for the duration of the glow cycle.
3
Trace the wiring harness from the GPCM to cylinder 11, inspecting for breaks, corrosion, or heat damage along the extended routing path.
4
Using a current clamp, measure actual current draw on the cylinder 11 feed wire during activation and compare to the other cylinders for consistency.
5
Inspect all bus bar connections on the bank that includes cylinder 11, ensuring torque specs are met and no oxidation is present at contact points.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
The PCM has detected a malfunction in the glow plug circuit for cylinder 11. This applies to large-displacement diesel engines with 11 or more cylinders. The glow plug for this cylinder is not functioning correctly, which affects cold-start combustion in that cylinder. The driver may notice extended...
The most common cause of P0681 (Cylinder 11 Glow Plug Circuit) is: Failed cylinder 11 glow plug (open or shorted)
Typical repair costs for P0681 range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive once the engine is running and warm. Cold-start performance will be degraded. On large engines, one non-functional glow plug is less impactful than on a 4-cylinder, but should still be repaired for reliability and emissions compliance.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0681 to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Cold Start / Glow Plug System
Difficulty
Type
Generic (SAE)
Recommended Tools
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