What Does P0673 Mean?
The PCM has detected a malfunction in the cylinder 3 glow plug circuit on a diesel engine. The circuit is not meeting expected electrical parameters, indicating the glow plug or its wiring has failed. Cylinder 3 will not receive proper pre-heating during cold starts, causing that cylinder to misfire until the engine warms up. The driver may notice extended cranking, rough running during warm-up, and white smoke from unburned fuel.
Common Causes
40%
Failed cylinder 3 glow plug
25%
Corroded or loose connection at cylinder 3 glow plug terminal
20%
Wiring fault between glow plug module and cylinder 3
10%
Glow plug control module failure on cylinder 3 output
5%
Carbon buildup around glow plug tip affecting heating performance
Diagnostic Steps
1
Remove the connector or bus bar from cylinder 3 glow plug and measure resistance. Expected range is 0.5-2.0 ohms at room temperature.
2
Measure all glow plugs to identify if only cylinder 3 is out of spec or if multiple plugs are degraded — glow plugs often age together and batch replacement is recommended.
3
Inspect the bus bar segment and terminal at cylinder 3 for corrosion, loose fit, or heat damage. These high-current connections must be clean and tight.
4
Verify power delivery to cylinder 3 during the glow cycle by measuring voltage at the bus bar with key on, engine off. Expected reading is battery voltage for the glow timer duration.
5
If the glow plug needs replacement and has been in service for over 100,000 miles, consider replacing all glow plugs as a set. Use penetrating oil and proper extraction technique to avoid breaking plugs in the head.
Estimated Repair Cost
$60 - $350
Parts + labor, varies by vehicle and location
The PCM has detected a malfunction in the cylinder 3 glow plug circuit on a diesel engine. The circuit is not meeting expected electrical parameters, indicating the glow plug or its wiring has failed. Cylinder 3 will not receive proper pre-heating during cold starts, causing that cylinder to misfire...
The most common cause of P0673 (Cylinder 3 Glow Plug Circuit) is: Failed cylinder 3 glow plug
Typical repair costs for P0673 range from $60 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Not a safety concern while driving. Cold-start performance will be degraded, especially in temperatures below 40°F. Extended cranking with failed glow plugs can wash cylinder walls and dilute engine oil with unburned fuel. Address before cold weather.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0673 to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Glow Plug System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
