Summary
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DTC P0670 stands for “Glow Plug Control Module Circuit/Open.” It means that the PCM has detected a problem with the glow plug control module or its circuit.
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Faulty glow plugs, a malfunctioning glow plug control module, and circuit problems are some of the issues that could trigger the code.
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Some symptoms of the P0670 code include engine knocking when the engine is cold, a lack of power when the engine is cold, and a lit check engine light.
The P0670 trouble code indicates a Glow Plug Control Module Circuit Malfunction. This diagnostic trouble code (DTC) is commonly found in diesel-powered vehicles and points to an issue with the electronic system that controls the glow plugs—essential components for cold engine starts.
When the glow plug control module fails or its circuit malfunctions, the engine may struggle to start, especially in colder climates. If left unresolved, the issue could affect emissions and fuel economy.
Common Symptoms of P0670
Recognizing the signs of a P0670 code can help prevent costly repairs and extended downtime. Common symptoms include:
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Hard starting, especially in cold weather
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Rough idle during startup
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Illumination of the check engine light
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Decreased fuel efficiency
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Increased white smoke from the exhaust
These symptoms can overlap with other diesel engine problems, so accurate diagnostics is crucial.
What Causes the P0670 Code?
The P0670 code can be triggered by several issues in the glow plug system. Here are the most common culprits:
Failed Glow Plug Control Module
The module responsible for regulating power to glow plugs may fail due to electrical stress or age.
Corroded or Damaged Wiring
Wiring harnesses or connectors to the glow plug system can corrode, fray, or disconnect over time.
Faulty ECM
In rare cases, the Engine Control Module may send incorrect signals to the glow plug system.
Circuit Issues
Internal shorts, open circuits, blown fuses, or poor ground connections can disrupt power flow.
Understanding the root cause is vital for a successful repair.
How to Diagnose and Fix Code P0670
Diagnosing the P0670 glow plug module issue requires professional tools capable of deep system scanning. Here’s a step-by-step approach:
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Use an advanced scan tool to confirm the P0670 code and check for related glow plug or control circuit faults.
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Inspect wiring and connectors around the glow plug control module for corrosion, damage, or looseness.
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Test the glow plug control module itself for voltage and resistance readings.
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Check fuses and relays related to the glow plug system.
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Replace the glow plug control module if confirmed faulty.
Recommended Diagnostic Tool: iCarsoft CR Ultra
To efficiently identify and fix the P0670 code on diesel engines, we recommend the iCarsoft CR Ultra—a professional-grade diagnostic scanner designed for both diesel and gasoline vehicles.
Why Choose iCarsoft CR Ultra?
Full System Diagnosis
Covers engine, glow plug modules, ECM, and all major vehicle systems for comprehensive troubleshooting.
Broad Vehicle Coverage
Supports over 60 car brands including Ford PowerStroke, GM Duramax, and Ram Cummins diesel models.
Advanced Functions
Live data stream, ECU coding, and bi-directional testing to actively diagnose glow plug system issues.
User-Friendly Design
Easy-to-use interface with 10-inch touchscreen—ideal for both professionals and serious DIYers.
For those searching for an affordable and reliable P0670 code fix for diesel engines, the CR Ultra delivers exceptional value and accuracy.
Frequently Asked Questions
Is it safe to drive with a P0670 code?
Driving with the P0670 code is possible but not recommended—especially in cold weather, where a non-functioning glow plug system can cause starting issues and rough engine operation.
Can I fix the P0670 code myself?
If you’re familiar with automotive electrical systems and have the right tools like the CR Ultra, you may be able to inspect and replace the faulty glow plug control module yourself. Otherwise, consult a professional.
What vehicles are commonly affected by P0670?
The P0670 code is commonly seen in diesel engines from manufacturers like Ford (PowerStroke), GM (Duramax), Chrysler/Ram (Cummins), Volkswagen, and Mercedes-Benz.
Final Thoughts
The P0670 code may seem minor, but ignoring it can result in major cold start problems and reduced engine efficiency. By using a comprehensive diagnostic tool like the iCarsoft CR Ultra, you can get to the root of the problem quickly and accurately.
Whether you're a DIY enthusiast or a seasoned technician, resolving glow plug control issues with the right tools ensures your diesel engine performs optimally year-round.
