P067FCylinder 6 Glow Plug Control Circuit High
The control circuit voltage for the cylinder 6 glow plug is stuck above the expected range, indicating a short to voltage or a failed glow plug module driver.
Definition
The glow plug control module monitors the voltage on each plug's control circuit and compares it to the commanded state. P067F sets when the cylinder 6 circuit reads high when the plug should be off or driven low. The plug may fail to heat, causing hard cold starts, white smoke, and a MIL, or it may remain powered continuously and overheat — an overheated glow plug can deform or break off inside the cylinder. The engine typically starts and runs normally once warm.
Common causes
- Cylinder 6 control wire shorted to battery voltage
- Failed driver stage in the glow plug control module
- Internally shorted cylinder 6 glow plug
- Water intrusion or corrosion in the module or plug connector
- Harness chafe against a powered circuit near the engine
Common misdiagnoses
- Replacing the full glow plug set for a single-circuit electrical fault
- Swapping the glow plug control module without checking for a wiring short
- Charging system diagnosis for the high-voltage reading
- PCM replacement
Troubleshooting steps
1.Check for related codes
Note whether P067E (cylinder 6 control circuit low) or other cylinder codes accompany it, which changes the fault picture toward the module.
2.Backprobe the cylinder 6 control circuit
With the glow system off, any battery voltage present on the control wire confirms a short to power or stuck driver.
3.Isolate wiring from module and plug
Disconnect both ends; voltage remaining on the wire means a harness short, no voltage means the module driver is at fault.
4.Resistance-test the glow plug
Compare cylinder 6 to a known-good plug; a shorted element reads abnormally low.
5.Retest after a cold soak
Clear the code and confirm it stays away through a full cold-start glow cycle.