P0677 Glow plugs: circuit fault (cylinder 7)

By: Diagno editorial team · Updated: 2026-10-15

P0677 means: Glow plugs: circuit fault (cylinder 7). Glow plugs heat the diesel engine's cylinders for cold starts. Drive gently and have the car checked soon. The repair usually costs about €40–300 in Estonia. The most common cause: connector loose, damp or corroded. Other possible causes: wire broken or chafed, faulty glow plug or its module.

What it means

Glow plugs heat the diesel engine's cylinders for cold starts. The computer found a fault in a plug or the glow plug module circuit. The computer found a fault in the electrical circuit: the part, a wire, a connector or a fuse.

What you may notice

• Hard cold starts
• White smoke after starting
• Glow plug light flashing

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire broken or chafed
3. 3Faulty glow plug or its module
4. 4Engine computer fault (rare)

Repair difficulty: Moderate

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? In cold weather start the engine only once the glow plug light has gone out. Fix it before the frosts if you can. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the glow plug or its module

Standard SAE description: Cylinder 7 Glow Plug Circuit