OBD-II Error Code P0671: Glow Plug 1 Cylinder Circuit Malfunction – How to Fix It

Medium 1-2 hours Medium Severity Verified July 2026
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Error Code
P0671
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours
Error code P0671 indicates a problem with the glow plug circuit for cylinder 1 in your diesel engine. This can cause hard starting, rough idle, or increased emissions. This guide will help you diagnose and fix the issue step by step.
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Tools You'll Need

How to Fix Error Code P0671

  1. Check for Other Codes

    Ensure the engine is off and cool before working on glow plugs.

  2. Locate the Glow Plug 1

  3. Visual Inspection

  4. Test Glow Plug Resistance

    Do not touch the glow plug when it's hot; let it cool completely.

  5. Test Power Supply

    Be careful not to short the probe against ground.

  6. Replace Glow Plug 1 if Faulty

    Over-tightening can damage the cylinder head. Use a torque wrench.

  7. Clear Codes and Test

    If the light comes back, recheck for codes or consult a mechanic.

Parts You May Need

Glow plug (cylinder 1)
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Glow plug (cylinder 1)
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Glow plug (cylinder 1)
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Glow plug (cylinder 1)
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When to Call a Professional

If you are not comfortable working with electrical systems or if the issue persists after replacing the glow plug, consult a professional mechanic. Also, if you suspect a faulty ECU or wiring harness issue beyond basic repairs, professional diagnosis is recommended.

Frequently Asked Questions

Can I drive with error code P0671?
It is not recommended. Driving with a faulty glow plug can cause hard starting, poor performance, and increased emissions. It may also lead to more serious engine issues over time.
How much does it cost to fix P0671?
Replacing a single glow plug typically costs between $100 and $300 including parts and labor. A DIY fix can cost around $20–$50 for the part.
Can a bad glow plug cause engine damage?
Yes, if left unfixed, a faulty glow plug can lead to incomplete combustion, which can damage the catalytic converter, increase carbon buildup, and cause cylinder misfires.
What tools do I need to test a glow plug?
You'll need a multimeter to check resistance and voltage. An OBD2 scanner is also helpful to read and clear the code.
Is code P0671 specific to a certain vehicle?
No, P0671 is a generic OBD-II code for any diesel vehicle. However, the exact location of cylinder 1 and glow plug specifications vary by make and model.

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