The P0671 trouble code is a diagnostic trouble code (DTC) that indicates a malfunction in the glow plug circuit for cylinder 1 in diesel engines. Glow plugs are essential for preheating the cylinders to facilitate ignition, especially in cold weather. When the powertrain control module (PCM) detects an abnormal voltage reading from the glow plug circuit, it triggers the P0671 code. This can lead to difficulties starting the engine, increased emissions, and reduced performance. Understanding this code is crucial for vehicle owners and DIY mechanics to ensure proper vehicle function and prevent further issues.
| P0671 Code Meaning | P0671 Code Common Causes |
|---|---|
| Cylinder 1 Glow Plug Circuit/Open | Failed glow plug |
| Abnormal voltage detected in glow plug circuit | Faulty glow plug control module |
| Glow plug circuit wiring issues | Damaged wiring harness |
| PCM malfunction | Faulty glow plug relay |
| Open or shorted circuits in the glow plug system |
Symptoms of P0671 Code
When the P0671 code is triggered, vehicle owners may notice several symptoms:
- Difficulty starting: The engine may take longer to start or may not start at all, especially in cold weather.
- Engine performance issues: There may be a noticeable lack of power until the engine warms up sufficiently.
- Excessive smoke: White smoke may be emitted from the exhaust during startup due to unburnt fuel.
- Check Engine Light: The illumination of the check engine light on the dashboard is a common indicator of this trouble code.
Technical Explanation
The PCM monitors the voltage levels in the glow plug circuit. Each cylinder typically has its own glow plug that heats up before and during engine ignition. If the PCM detects that the voltage reading from cylinder 1’s glow plug is outside of specified parameters, it will store the P0671 code. This could indicate that the glow plug itself is faulty, there are issues with the wiring harness, or that other components like the control module are malfunctioning.
Step-by-Step Diagnosis
Diagnosing a P0671 code involves several steps:
- Visual Inspection: Begin with a thorough visual inspection of the glow plugs, wiring harnesses, and connectors for any signs of damage or corrosion.
- Check for Related Codes: Use an OBD-II scanner to check if there are any other trouble codes present that could provide additional context.
- Test Glow Plug Resistance: Disconnect the glow plug connector and use a multimeter to measure resistance. A healthy glow plug typically shows resistance between 0.5 to 2 ohms.
- Inspect Wiring: Check for continuity in the wiring leading to cylinder 1’s glow plug. Look for any breaks or shorts in the wiring.
- Control Module Check: If no issues are found with the glow plugs or wiring, inspect the glow plug control module for faults.
- Clear Codes and Test Drive: After repairs are made, clear any stored codes and take the vehicle for a test drive to see if the P0671 code reappears.
Solution Methods
To address a P0671 trouble code effectively:
Replace Faulty Glow Plug
- Symptoms: If testing reveals that the glow plug has high resistance or no continuity, it should be replaced.
- Cost Estimate: The cost for parts can range from $20 to $100 per glow plug depending on make and model. Labor costs can add another $50 to $100.
Repair Wiring Issues
- Symptoms: Look for frayed wires or loose connections.
- Solution: Repair or replace damaged wires and ensure all connections are secure.
- Cost Estimate: Depending on severity, repairs can range from $50 to $200.
Replace Glow Plug Control Module
- Symptoms: If multiple tests indicate issues beyond just one glow plug, consider replacing the control module.
- Cost Estimate: Replacement modules can cost between $100 and $300 plus labor.
Inspect and Replace Relay
- Symptoms: If there’s intermittent starting issues even after replacing components.
- Solution: Test and replace any faulty relays associated with the glow plugs.
- Cost Estimate: Relays typically cost around $20 to $50.
Warnings and Recommendations
- Always ensure that you disconnect battery power before working on electrical components to avoid shocks or shorts.
- Be cautious when handling hot components; glow plugs can become extremely hot during operation.
- If you are not confident in your ability to diagnose or repair these issues, seek professional assistance to avoid further damage to your vehicle.
Closing Paragraph
The P0671 trouble code signifies an important issue within your diesel engine’s starting system related to cylinder 1’s glow plug circuit. By understanding its symptoms, causes, and solutions, vehicle owners and DIY mechanics can effectively diagnose and rectify this problem. Regular maintenance checks on your vehicle’s electrical systems can prevent such issues from arising in the future, ensuring reliable operation throughout all seasons.
Frequently Asked Questions About P0671
- What does P0671 mean?
The P0671 code indicates a malfunction in the glow plug circuit for cylinder 1. - How serious is a P0671 code?
This 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 avoid further damage. - How do I reset a P0671 code?
You can reset it using an OBD-II scanner after addressing any underlying issues. - What tools do I need to diagnose P0671?
A multimeter and an OBD-II scanner are essential tools for diagnosing this trouble code. - How often should I check my glow plugs?
It’s recommended to inspect them every 60,000 miles or as specified by your vehicle’s manufacturer. - What vehicles commonly experience P0671?
This issue is prevalent in diesel engines across various makes and models. - Should I attempt repairs myself?
If you’re experienced with automotive repairs, you may try; otherwise, consult a professional mechanic.