DURAMAX-P0677 moderate Duramax ›

Cylinder 7 Glow Plug Circuit

The DURAMAX-P0677 (Duramax) diesel fault code means: Cylinder 7 Glow Plug Circuit. This is a moderate severity code.

My Garage →
Keep driving?
Yes, but fix soon
DIY difficulty
intermediate
Mobile mechanic network · I-5 corridor pilot

Down with a Duramax fault on the road?

We are building a network of verified mobile diesel and reefer technicians along the freight corridor. It is not live yet — no one can be dispatched to you today. You can see where the pilot is launching and register interest.

View pilot availability →
Built for Diesel — Not a Car Reader
ANCEL HD7000 Heavy-Duty Diesel Scanner

A $30 car code reader can't do diesel. The HD7000 reads full-system codes and does parked DPF regen, idle/speed-limit, and service resets from the cab — on everything from a 6.7 Cummins/Power Stroke/Duramax pickup to Class-8 trucks (Detroit, Paccar, CAT, Volvo, Mack, International).

Check Price on Amazon
FOXWELL HD301 Diesel Truck Scanner
Lower-Cost Diesel Option
FOXWELL HD301 Diesel Truck Scanner

Full-system 6/9/16-pin diesel scan tool for Cummins, Paccar, CAT, Detroit and more — plug-and-play, no subscription. A cheaper way to read heavy-duty codes a basic OBD2 scanner skips entirely.

Check Price on Amazon

Affiliate links — we earn a commission at no extra cost to you.

What Are the Symptoms of DURAMAX-P0677?

  • Check Engine Light on
  • Hard starting when cold
  • White smoke or rough running after a cold start

What Causes DURAMAX-P0677? (Most Likely First)

  • Failed cylinder 7 glow plug High
  • Damaged wire or loose connection at the glow plug High
  • Glow plug controller fault Low

Can I Still Drive with DURAMAX-P0677?

Yes, but fix soon. DURAMAX-P0677 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring it.

Frequently Asked Questions

What does P0677 mean on a Duramax?

P0677 means Cylinder 7 Glow Plug Circuit. The glow plug control system has detected a fault in the circuit for the cylinder 7 glow plug.

Is P0677 a Duramax-specific code?

No. P0677 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions GM uses to set it on its diesels are in GM service information.

Mechanics Guide Step-by-step diagnosis

How Do You Diagnose DURAMAX-P0677?

  1. Measure the cylinder 7 glow plug resistance and compare it with the other cylinders and the specification.

  2. Inspect the glow plug wire and terminal.

  3. Check the controller output to cylinder 7 if the plug and wiring test good.

Sources 1

This page is built from documented references. Verify against your own service info before repair work.

  • SAE J2012Diagnostic Trouble Code Definitions (defines P0677 as a generic OBD-II code)

P0677 on Other Platforms

The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:

Gas / Automotive (OBD-II) Generic OBD-II definition for P0677

Explore More

More Duramax codes → Diesel home All diesel codes Heavy-duty Guides

Was this helpful?

Send this to whoever is fixing the truck — your tech, or the person asking what the fault means.