P0671
UniversalCylinder 1 Glow Plug Circuit
Medium SeverityThis code indicates that the powertrain control module (PCM) has detected a malfunction in the electrical circuit for the Cylinder 1 Glow Plug. This issue primarily affects the vehicle's ability to start in cold weather, potentially leading to prolonged cranking or rough initial engine operation.
⚠️ Before You Begin (Safety First)
Always practice caution when working on a vehicle's electrical system and hot engine components. Ensure the engine is cool before touching parts, and disconnect the battery before performing any electrical repairs to prevent accidental shorts or injury.
Common Symptoms
- Check Engine Light illumination
- Difficulty starting the engine in cold weather
- Rough idling immediately after a cold start
- White smoke from the exhaust during cold starts
Common Causes
- Faulty Cylinder 1 glow plug
- Damaged or corroded wiring to the Cylinder 1 glow plug
- Problem with the glow plug control module/relay
- Blown fuse related to the glow plug circuit
Frequently reported on: Ford F-Series (diesel) 2003-2010, Ram 2500/3500 (diesel) 2007-2012, Chevrolet Silverado/GMC Sierra (Duramax diesel) 2001-2007, Volkswagen TDI models 2004-2009
Diagnostic Steps
- Inspect the wiring and connectors leading to the Cylinder 1 glow plug for any visible damage, corrosion, or loose connections.
- Carefully remove the Cylinder 1 glow plug and test its resistance with a multimeter. A healthy glow plug typically shows very low resistance (0.5 to 2.0 ohms). Infinite resistance or very high resistance indicates a faulty glow plug.
- If the glow plug tests faulty, replace it with a new one.
- If the glow plug is good, check the glow plug control module/relay for proper operation and ensure the circuit receives proper voltage.
- Clear the code with an OBD-II scanner after repairs and test the vehicle.
👨🔧 When to Call a Professional
While replacing a glow plug can often be a DIY task, you should call a professional if you encounter a seized glow plug that won't easily come out, as attempting to force it can lead to damage to the cylinder head. Also, if extensive electrical diagnosis is required beyond a simple glow plug replacement, professional help is advised.
Commonly Asked Questions
What specifically does the P0671 code mean for my engine?
P0671 indicates that there's an electrical fault within the circuit that powers the glow plug for cylinder number one. This plug heats the combustion chamber to aid in cold starting diesel engines.
Can I continue to drive my car with a P0671 code?
Yes, you can typically drive with this code, but you may experience significantly harder starts in cold weather, increased exhaust smoke on startup, and potentially a rough idle until the engine warms up. It's best to address it promptly to prevent more serious issues.
How can I test the Cylinder 1 glow plug to confirm if it's faulty?
You can test the glow plug by disconnecting its electrical connector and measuring its resistance across the terminals using a multimeter. A good glow plug will have very low resistance (usually less than 2 ohms). An open circuit (infinite resistance) or very high resistance indicates a failed glow plug.
Are there any other components I should check if the glow plug itself is fine?
Yes, if the glow plug tests good, you should inspect the wiring harness for damage, check the glow plug relay or control module for proper function, and ensure that any relevant fuses in the glow plug circuit are not blown.
Is it difficult to replace a glow plug myself?
Replacing a glow plug can range from medium to advanced difficulty, depending on its location and how seized it is. It often requires specific tools and care to avoid breaking the plug in the cylinder head, which would require much more extensive repairs.