The P0671 trouble code is a diagnostic trouble code (DTC) that indicates a malfunction in the glow plug circuit for cylinder 1 of a diesel engine. This code is crucial for diesel engines that rely on glow plugs to preheat the combustion chamber for efficient starting, especially in cold weather. When the Powertrain Control Module (PCM) detects an issue with the glow plug circuit, it triggers the P0671 code, which can lead to starting difficulties and increased emissions if not addressed promptly.
| P0671 Code Meaning | P0671 Code Common Causes |
|---|---|
| Cylinder 1 Glow Plug Circuit/Open | Failed glow plug |
| Abnormal voltage reading in the glow plug circuit | Faulty glow plug control module |
| Open or shorted wiring in the glow plug circuit | Damaged wiring harness |
| PCM malfunction | Faulty glow plug relay |
Symptoms of P0671 Code
Understanding the symptoms associated with the P0671 code is essential for timely diagnosis and repair. Common symptoms include:
- Difficulty starting the engine, especially in cold weather
- Engine misfires or runs roughly during startup
- White smoke from the exhaust during cold starts
- Illuminated check engine light
- Increased fuel consumption
Technical Explanation of P0671 Code
The P0671 code is triggered when the PCM identifies an issue with the glow plug circuit of cylinder 1. Each cylinder in a diesel engine has a dedicated glow plug that heats up to facilitate ignition. The PCM monitors the voltage across the glow plug circuit; if it detects an abnormal voltage or a failure to heat, it sets this trouble code.
How Glow Plugs Work
Glow plugs are heating elements that preheat the air in the combustion chamber before ignition. They are essential for diesel engines, particularly during cold starts. The PCM controls these plugs and monitors their operation through voltage readings.
Step-by-Step Diagnosis of P0671 Code
Diagnosing the P0671 code involves several steps:
- Visual Inspection: Start by inspecting the wiring and connectors associated with the glow plug circuit for any visible damage or corrosion.
- Check Glow Plug Resistance: Use a digital multimeter to check the resistance of the glow plug. The resistance should typically be between 0.5 to 2.0 ohms. If it falls outside this range, replace the glow plug.
- Test Wiring Continuity: Check for continuity in the wiring harness leading to the glow plug. Any breaks or shorts can cause issues.
- Inspect Glow Plug Control Module: Test the functionality of the glow plug control module, as failures here can also trigger this code.
- Scan Tool Usage: Use an OBD-II scanner to clear codes and monitor live data while attempting to start the engine again.
- Check PCM: If all other components check out, consider testing or reprogramming the PCM as it may be malfunctioning.
Solution Methods for P0671 Code
Addressing a P0671 code involves several potential solution methods:
- Replace Faulty Glow Plug: If testing reveals a faulty glow plug, replace it with a new one.
- Repair Wiring Issues: Fix any damaged wiring or connectors that may be causing an open or short circuit.
- Replace Glow Plug Control Module: If diagnostics indicate a failure in this component, replacing it may resolve the issue.
- Reprogram or Replace PCM: In rare cases where all else fails, consider reprogramming or replacing the PCM.
Cost Estimates
The cost for repairs related to a P0671 code can vary widely based on location and vehicle make/model:
- Glow Plug Replacement: $100 – $300 (including parts and labor)
- Wiring Repairs: $50 – $200 depending on extent of damage
- Glow Plug Control Module Replacement: $200 – $600
- PCM Reprogramming/Replacement: $300 – $1000
Warnings and Recommendations
- Always ensure safety when working on electrical components; disconnect the battery before starting repairs.
- If you are inexperienced with automotive repairs, consider seeking professional assistance to avoid potential damage to your vehicle.
- Regularly inspect your vehicle’s electrical systems to prevent issues from developing into more serious problems.
Frequently Asked Questions About P0671
- What does error code P0671 mean?
The P0671 code indicates a problem with the glow plug circuit in cylinder 1 of a diesel engine. - How serious is a P0671 code?
This code can lead to starting issues and increased emissions if not addressed promptly. - Can I drive my car with a P0671 code?
Driving with this code may lead to poor performance; it’s advisable to address it as soon as possible. - How do I reset a P0671 code?
You can reset this code using an OBD-II scanner after addressing any underlying issues. - What tools do I need to diagnose P0671?
A digital multimeter and an OBD-II scanner are essential for diagnosing this trouble code. - Is replacing a glow plug difficult?
Replacing a glow plug can be straightforward but may require specific tools; consult your vehicle’s manual. - What if multiple cylinders show codes related to glow plugs?
This could indicate an issue with the control module or wiring; further diagnostics are necessary. - When should I seek professional help for P0671?
If you’re unsure about diagnosing or repairing electrical components, it’s best to consult a professional mechanic.
In conclusion, dealing with a P0671 trouble code requires careful diagnosis and appropriate repairs to ensure your diesel engine operates efficiently and reliably. By understanding how glow plugs function and following systematic diagnostic steps, vehicle owners and DIY mechanics can effectively address this issue and maintain their vehicles’ performance.