P0671 Code: Here's How to Solve It Fast

The P0671 trouble code is a diagnostic trouble code (DTC) that indicates an issue with the glow plug circuit for cylinder 1 in diesel engines. Specifically, it means that the powertrain control module (PCM) has detected a malfunction in the glow plug circuit, which is essential for heating the combustion chamber before starting the engine. This code can lead to starting difficulties, especially in cold weather, and may trigger other performance issues if not addressed promptly.

P0671 Code Meaning	P0671 Code Common Causes
Cylinder 1 Glow Plug Circuit/Open	Failed glow plug
Malfunctioning glow plug control module	Damaged wiring harness
Faulty PCM (Powertrain Control Module)	Short or open circuit in the glow plug system
Faulty glow plug relay	Corroded or loose connections

Symptoms of P0671 Code

Symptoms

• Difficulty starting the engine, especially in cold weather
• Engine misfires or runs roughly during startup
• White smoke from the exhaust on startup
• Illuminated check engine light
• Lack of power until the engine warms up

Technical Explanation of P0671 Code

The P0671 code is primarily associated with diesel engines that utilize glow plugs to preheat the combustion chamber. Each cylinder typically has its own glow plug, which heats up quickly when activated by the PCM. If there is a failure in the glow plug or its associated circuitry, the PCM will set the P0671 code.

Step-by-Step Diagnosis

1. Visual Inspection: Begin by inspecting the wiring and connectors associated with the glow plug circuit for any signs of damage or corrosion.
2. Use a Multimeter: Check the resistance of the glow plug using a multimeter. A reading between 0.5 to 2 ohms typically indicates a functional glow plug.
3. Check Glow Plug Control Module: Inspect and test the glow plug control module for proper operation. Ensure that it is receiving adequate voltage and functioning correctly.
4. Test Wiring Harness: Examine the wiring harness for continuity and check for shorts or opens within the circuit.
5. Clear Codes and Retest: After repairs, clear any stored codes from the PCM and retest to see if the P0671 code reappears.

Solution Methods for P0671 Code

Glow Plug Replacement

Symptoms

• Hard starting
• Engine misfires

Technical Explanation

If a glow plug fails, it will not heat properly, leading to poor combustion and difficult starts.

Step-by-Step Diagnosis

1. Remove the faulty glow plug.
2. Test it with a multimeter.
3. Replace if readings are out of specification.

Cost Estimates

• Glow plugs typically cost between $20 to $100 each, depending on brand and vehicle type.

Warnings and Recommendations

Always replace glow plugs in sets to ensure even performance across all cylinders.

Glow Plug Control Module Replacement

Symptoms

• Persistent check engine light
• Starting issues despite good glow plugs

Technical Explanation

The control module regulates power to the glow plugs; if it fails, it may not activate them properly.

Step-by-Step Diagnosis

1. Disconnect and inspect the control module.
2. Test for voltage output.
3. Replace if defective.

Cost Estimates

• Control modules can range from $100 to $300 depending on make and model.

Warnings and Recommendations

Ensure proper installation to avoid damage to new components.

Wiring Harness Repair/Replacement

Symptoms

• Intermittent starting issues
• Visible damage to wiring

Technical Explanation

Damaged wiring can interrupt power supply to the glow plugs, causing them not to heat up adequately.

Step-by-Step Diagnosis

1. Inspect all wiring connected to the glow plugs.
2. Repair or replace any damaged sections.
3. Ensure all connections are secure.

Cost Estimates

• Repairing wiring can be inexpensive, but replacement harnesses may cost between $50 to $200.

Warnings and Recommendations

Check for corrosion at connectors as well; this can lead to poor connections.

Closing Paragraph

In summary, addressing a P0671 trouble code promptly is crucial for maintaining optimal engine performance in diesel vehicles. By understanding its meaning, symptoms, and potential solutions, vehicle owners and DIY mechanics can effectively diagnose and rectify issues related to this code. Always consult your vehicle's repair manual for specific instructions tailored to your model, and when in doubt, seek professional assistance to avoid further complications.

Frequently Asked Questions About P0671

• What does P0671 mean?
  The P0671 code indicates a malfunction in the glow plug circuit for cylinder 1 in diesel engines.
• How serious is a P0671 code?
  A P0671 code can lead to starting difficulties and poor engine performance if not addressed.
• Can I drive my car with a P0671 code?
  While you may be able to drive short distances, it's advisable to fix this issue promptly to prevent further damage.
• What tools do I need to diagnose P0671?
  A multimeter for testing resistance and an OBD-II scanner for reading codes will be necessary.
• Should I replace all glow plugs if one fails?
  Yes, it's recommended to replace all glow plugs simultaneously for consistent performance.
• How much does it cost to fix a P0671 code?
  The cost can vary widely but generally ranges from $100 to $600 depending on parts needed.
• Can I fix P0671 myself?
  If you have basic mechanical skills and tools, you can attempt repairs; otherwise, consult a professional.
• What are common mistakes when diagnosing P0671?
  Failing to check wiring integrity or assuming only one component is faulty without thorough testing.