P0673
Cylinder 3 Glow Plug Circuit
Powertrain Ignition System Diesel Glow Plug 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The glow plug for cylinder 3 isn't heating up properly before the engine starts, like a broken lighter that won't ignite. The ECU detected a circuit problem preventing the glow plug from reaching the correct temperature.

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Symptoms You May Notice
3 known symptoms for this code
Difficult cold starting, especially in cold weather
White smoke from exhaust on startup
Rough idle after cold start
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the glow plug circuit voltage and resistance during the glow plug pre-heat cycle. It expects a specific voltage drop and current draw within a set timeframe before combustion. If resistance is too high, voltage is insufficient, or the circuit opens/shorts, the fault is triggered.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Glow plug circuit voltage 11-14V during pre-heat cycle <5V or open circuit detected
Glow plug resistance 0.5-2 ohms when cold >10 ohms or infinite resistance
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Glow plug relay
Test and replace the glow plug relay if it's stuck open; this is the cheapest common cause.
2
Glow plug for cylinder 3
Remove and test the glow plug resistance with a multimeter; replace if open or excessive resistance detected.
3
Engine harness/connectors
Inspect and clean corroded connectors on the glow plug circuit and repair any damaged wiring.