P0680Cylinder 10 Glow Plug Circuit
An electrical fault has been detected in the glow plug circuit for cylinder 10, applicable to V10 and V12 diesel engines.
Definition
On diesels with ten or more cylinders, the glow plug control module checks each plug circuit for proper voltage and current whenever a glow cycle is commanded. P0680 sets when the cylinder 10 circuit is open, shorted, or out of its expected current range. Typical symptoms are extended cranking and rough running on cold starts, white smoke, and an illuminated MIL, with little effect once the engine is warm. Continued operation increases cold-start emissions and fuel dilution of the oil.
Common causes
- Failed cylinder 10 glow plug (open element)
- Corroded or loose terminal at the glow plug
- Open or shorted feed wire between the module and cylinder 10
- Failed glow plug control module output driver
- Degraded ground path adding circuit resistance
Common misdiagnoses
- Replacing every glow plug when one circuit is faulty
- Replacing the glow plug relay/module before testing the plug
- Battery replacement for the hard-start complaint
- PCM replacement
Troubleshooting steps
1.Review all stored glow plug codes
Faults on multiple cylinders suggest a shared module, fuse, or ground problem instead of a single plug.
2.Measure the cylinder 10 plug's resistance
Disconnect the terminal and measure to ground; an open (OL) reading confirms a burned-out element.
3.Inspect the harness run
Check for heat damage and chafing where the cylinder 10 feed wire routes across the engine.
4.Command a glow cycle and check for output
Verify supply voltage reaches the cylinder 10 terminal while the scan tool commands the plugs on.
5.Condemn the module last
Only replace the glow plug control module when the plug and wiring both test good but the cylinder 10 output is dead.