P0677 Cylinder 7 Glow Plug Circuit

P0677 indicates a cylinder 7 glow plug circuit fault. The controller detected an electrical fault in the glow plug circuit for cylinder 7.

Code details

Generic OBD-II · P0

System: Computer
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace a bank of glow plugs until cylinder 7 has been compared against known good circuits.

Symptoms of P0677

Check-engine light, sometimes with several unrelated codes at once.
Warning lights, a no-start, or intermittent electrical faults.
Communication or module-reset problems on a scan tool.

Common causes of P0677

Low battery voltage, poor grounds, corroded connectors, or blown fuses.
Wiring or network (CAN bus) faults between modules.
A module software/programming issue, or rarely a failed controller.

Useful checks before replacing parts

Check cylinder 7 glow plug resistance, commanded voltage, current draw, battery condition, coolant temperature, and freeze-frame cold-start data.
Inspect cylinder 7 connector terminals, module output, harness heat damage, corrosion, rubbed wiring, and shorts to ground or power.
Compare cylinder 7 current draw against the other bank or neighboring cylinders to isolate the failed load or circuit branch.

Related OBD-II codes

These nearby computer entries can help compare wording and pin down the fault area.