OBD-II Generic Error Code P0674: How to Fix It

Medium 1-2 hours Medium Severity Verified June 2026
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Error Code
P0674
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours
Error code P0674 indicates a problem with the glow plug in cylinder 4 of your diesel engine. Glow plugs help heat the combustion chamber for cold starts, and this code means the glow plug or its circuit is malfunctioning. This guide will help you diagnose and fix the issue.
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Tools You'll Need

How to Fix Error Code P0674

  1. Safety First: Disconnect Battery

    Always disconnect the battery before working on electrical components.

  2. Locate Glow Plug 4

  3. Test Glow Plug Resistance

    Do not touch the glow plug tip with bare hands; oil can cause premature failure.

  4. Replace Faulty Glow Plug

    Over-tightening can break the glow plug in the head, requiring extraction.

  5. Check Wiring and Connectors

  6. Reconnect Battery and Clear Codes

  7. Test Drive and Recheck

Parts You May Need

Glow plug
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Glow plug
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Glow plug
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Glow plug
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When to Call a Professional

If you are uncomfortable working with electrical systems, or if the code returns after replacing the glow plug, call a professional mechanic. Also, if the glow plug breaks during removal, an extraction tool or head removal may be required.

Frequently Asked Questions

Can I drive with error code P0674?
Yes, but starting in cold weather may be difficult, and the engine may run rough. It's best to fix it promptly.
How much does it cost to fix P0674?
DIY cost is around $20-$50 for a glow plug. Mechanic labor can range from $100-$300 depending on vehicle and accessibility.
Can one bad glow plug cause the check engine light to come on?
Yes, a faulty glow plug will trigger the check engine light and store code P0674.
What tools do I need to replace a glow plug?
A multimeter, OBD2 scanner, deep socket, ratchet, torque wrench, and possibly a swivel adapter for tight spaces.
Will a bad glow plug damage the engine?
Not directly, but it can cause hard starting, misfires, and increased emissions. Over time, unburnt fuel can damage the catalytic converter.

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