What causes a P0677 code?

P0677 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a P0677 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0677 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

OBD-II

P0677

Cylinder 7 Glow Plug Circuit / Open

What it means

The Engine Control Module (ECM) has detected a voltage or resistance deviation in the glow plug circuit for cylinder number 7. This indicates an electrical failure in the heater element or the associated wiring harness.