Cylinder 3 Glow Plug Circuit
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.
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.
| 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 |
Code P0673 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0673 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.