P0677Powertrain
Powertrain · SAE
Glow Plug Cylinder 7 — Circuit
Meaning
The control module has detected an electrical fault in the glow plug circuit for cylinder 7. The glow plug may be open or shorted, or the control circuit may have a wiring fault.
Common causes
- Cylinder 7 glow plug open or shorted to ground
- Damaged or corroded connector or wiring to the glow plug
- Defective glow plug relay or glow plug control module (GSC)
- Glow plug mechanically broken due to overheating or age
- Loss of supply voltage or ground in the control circuit
Symptoms
- Check engine light illuminated
- Hard cold start
- Misfire or rough combustion at cylinder 7 in cold conditions
- Excessive smoke on first start-up
- Possible power reduction during initial warm-up
Severity
Moderate: the engine starts but with difficulty in cold weather; if not addressed, severe starting problems or cylinder damage from prolonged misfiring may result.
What to do
- Measure glow plug resistance at cylinder 7 (typical 0.5–4 Ω); replace if open or shorted
- Inspect the glow plug connector and wiring for corrosion or breakage
- Check supply voltage at the relay or GSC module
- Use a scan tool to verify glow plug control module operation
- Replace the GSC module if wiring is intact but the circuit is not energised