P0680
Cylinder 10 Glow Plug Circuit
Powertrain Ignition System Glow plug circuit 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The glow plug for cylinder 10 isn't heating up properly, which makes cold diesel engine starts difficult. Think of it like a lighter that won't ignite—the engine needs that heat to start when it's cold.

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Symptoms You May Notice
3 known symptoms for this code
Hard starting in cold weather
Rough idle after cold start
Glow plug warning lamp illuminated
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors voltage and current draw from the cylinder 10 glow plug relay circuit during the glow plug pre-heat cycle. It detects open circuits, shorts, or excessive resistance that prevent proper heating. The circuit is typically energized for 5-10 seconds before cranking.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Glow plug circuit voltage 11-14V supply during preheat Below 10V or open circuit detected
Circuit current draw 5-15A per glow plug Zero amps or excessive current (short)
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Glow plug for cylinder 10
Remove the old glow plug and install a replacement; this is the most common fix.
2
Glow plug relay
Test relay with a multimeter and replace if it fails to energize the glow plug circuit.
3
Engine wiring harness connector
Inspect and clean the glow plug connector for corrosion or loose contacts.