How to Fix the P0670 Code on Duramax (The Expert Approach)

Vehicles with the OBD system use codes called “diagnostic trouble codes” to notify a specific problem. P0670 is one such code. When the code appears, a better way of dealing with the code is to ask what the code means.

In simple words, the P0670 indicates a problem with the glow plug of the Duramax engine.  More specifically, the glow plug circuit in cylinder 6 is faulty, which causes the glow plug to fail to heat up. ECM detects this issue and stores the code.

We aim to provide general guidelines on how to fix the code while the symptoms, causes, and severity will also be taken care of. Keep reading to find out more!

P0670 Code on Duramax

What Does P0670 Code Mean on Duramax?

To reiterate, the code indicates a problem with the glow plug of the Duramax engine. When the ECM detects an issue with the glow plug circuit, it stores the P0670 code.

Typically, a gas engine needs spark plugs to ignite the fuel in the cylinder, whereas a diesel engine needs a glow plug. Glow plugs require a properly functioning circuit for this job to be done nicely. Any fault in the circuit, on the other hand, prevents the glow plug from heating up and igniting.

The code is set as soon as the PCM detects a fault in the circuit. It can either be shorted, high or no voltage condition. Here is a break of the code P20b9. So you get a better understanding of the code.

  • P = denotes the vehicle’s powertrain. 
  • 0 = indicates a generic number derived from the SAE standard.
  • 6 = refers to the Glow plug.
  • 70 = indicates a fault in the Glow Plug Circuit

How Serious Is The Code P0670 On Duramax?

The code should be considered severe if more than one glow plug refuses to heat up. The effect will be minimal if only one plug is faulty. If more than one glow plug has issues, most likely, Duramax will not start.

There can be additional consequences too. If the combustion process does not occur on time, the engine’s overall performance may be reduced. In addition, you may get less fuel economy and less power from the engine. The issue can have other consequences, so solving the problem as soon as the code appears is a good idea.

When the outside temperature is below the freezing point, the cylinder head is very likely to freeze. Due to the cool cylinder head, heat generated in the cylinder is quickly lost. A glow plug, usually installed under the cylinder head, resolves the issue by initializing the combustion.

What Causes Code P0670 On Duramax?

A faulty glow plug control module circuit is a major reason for the code. There could be some other additional causes. Below is a list of them. Addressing and resolving these causes will almost certainly result in the code being removed.

  • Circuit shorted high or low.
  • Damaged wiring 
  • There may be loose wiring
  • Problems in the SCR or PCM controller
  • Loose connection
  • Poor electrical connection

Other Symptoms of Getting P0670 on Duramax?

The most obvious symptom is that you will have a difficult time starting the engine. Also, a fault in more than one glow plug circuit will likely prevent the engine from starting. The other symptoms include the following:

  • The engine light will appear 
  • engine performance will decrease 
  • May create white smoke
  • Unusual sound before starting the engine
  • PCM will set the code
  • Lack of power
  • Hard to start the engine 

How To Fix P0670 On Duramax?

When it comes to fixing the code, there can be two questions. Can I fix it on my own?  Or do I need professional help? Since it remains unclear as to what is causing the problem, it is a wise decision to fix the issue by getting professional help. 


Before starting the diagnosis, you’ll need a Duramax vehicle-specific repair manual corresponding to the make, year, and engine size.  The manual will provide all the necessary information, including step-by-step instructions, a wiring diagram, and other explanations.

Basic Tools Required

  • The OBD Scanner 
  • A digital Volt or ohmmeter 

Step 1: Collect Freeze frame data

You need an OBD scanner to find out the stored code. Put the scanner inside the OBD 2 port to get all the recorded data and clear it. Make sure the ignition is off, then start the ignition and observe the data again.

Step 2: Visual Inspection

The cause of the code can be as minor as a loose wiring connection or any other physical damage. In this step, visually inspect all the important places and locate the faulty wire and damage. Repairing all the damage might result in fixing the code. If it does not fix the issue, move on to the next step.

Step 3: Carry out the Resistance Test

You need a digital volt or ohmmeter to carry out the resistance test. The test’s purpose is to check if a steady power supply or voltage is maintained in the system.

Start by placing the red lead on the glow plug terminal and finding a good ground for the black lead. Now verify the voltage range with the suggested range found in the manual.

If the range is more than the specified range, you might have to replace the glow plug.

Step 4: Carry out the Resistance Test on the Glow Plug Wire

At this stage, you may need to check the voltage range of the glow plug relay to the bus bar. If the range is more than the suggested range, then the blame automatically goes to the wiring.

To resolve the code, particular components might need to be replaced.

  • Any connector and damaged wire 
  • Glow Plug
  • Glow plug relay
  • Glow plug circuit
  • Battery

How Much Does It Cost To Fix P0670 On Duramax?

Many things determine the cost of repairing the code P0670. Following the DIY approach to solving the issue will cost you more since you will need a scanner or an ohmmeter. The cost of these items ranges from $200 to $300.

You may expect to pay between $150 and $200 for hiring a professional. In addition, you may also pay for specific replacement parts, such as the circuit or the glow plug.

Can You Drive Your Duramax With Code P0670? 

As stated earlier, code P0670 should be considered moderately severe to severe. A glow plug is an important part of an automobile. Any damage to this part results in the engine not starting. If one plug is faulty, the engine may start, but you should not drive the car until the issue is resolved.


Duramax code P0670 should be taken seriously. The code notifies you about the possible error in the glow plug. Since the plug is a crucial component in the engine, you must take the necessary step as soon as the code appears.

When the code appears, start by asking about the severity and the meaning of the code. Get the best professional to fix the issue. While you may broaden your search, we believe this write-up will assist you in helping to solve the issue.

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