How to Fix the P0674 DTC Code on Duramax (Expert Guidance)

Duramax engines are significant. However, that doesn’t mean that they are without any flaws. While there is a flaw, diagnosis codes exist to make repairs easier for the owner.

PO674 is one such code that your Duramax car can diagnose. It is a Diagnosis Trouble Code (DTC) used to represent the issue where there are defects or malfunctions in the glowplugs on cylinder no. 4.

Once you have received the diagnosis, you can take certain steps to resolve it. So are you interested to know more about this DTC? Well then, what are you waiting for? Scroll down below and keep reading.

How to Fix the P0674 DTC Code on Duramax

What Does PO674 Code Mean On Duramax?

The PO674 is, as we have mentioned, a Diagnosis Trouble Code used by Duramax vehicles to express a specific issue. Each letter on this code has something that they represent. You can take a glance at the breakdown below.

  • P= It refers to the powertrain or network of modules used for maintaining the transmission energy.
  • O= A standard figure derived from SAE for cyber security.
  • 6= Computer auxiliary output
  • 74= Faulty computer system, in this case, the glowplugs in the 4th cylinder.

In the case of the PO674, the fault has nothing to do with the way you will be driving your vehicle. Instead, the problem lies with auxiliary systems like glowplugs.

In the case of this code, the issue lies with malfunctioning glowplugs in the computer mainframe, specifically in the 4th cylinder.

How Serious Is P0674 Code On Duramax?

While this issue isn’t so serious that it would affect the regular usage of your vehicle, it is still better that you fix it as soon as the problem appears.

Do not delay the fix when the problem appears. If left unaddressed, this could have adverse effects on your vehicle and its standard driving conditions in the long run.

Additionally, the malfunctioning glowplug can also cause other sensors in the car to be affected as well. As such, you might notice transmission issues or issues with other modules that depend on sensors throughout the vehicle.

What Causes P0674 Code On Duramax?

There could be several reasons or root issues that could cause the code to flash in your vehicle. We have compiled the most common ones and displayed them in the list below:

  • Malfunctioning of defective glowplug
  • Damaged, burnt, or disconnected wirings.
  • Connecters got disconnected or short-circuited.
  • Malfunctioning control module.
  • Problems with the glowplug relay timing.
  • Circuit failure or energy transportation failure leads to malfunctions.
  • PCM failure on the system that uses the same module as the glowplugs.

How To Fix PO674 Code On Duramax?

Before you can fix the code, you must first run a proper diagnosis. Only after running the diagnosis would one be able to identify the root cause of the problem and act accordingly.

Below, we have compiled the step-by-step procedure you need to follow when responding to the P0674 code after running a proper diagnosis.

Step 1: Run Scans

Make use of an OBD scanner to scan the computer system. Reset the computer and activate it to check whether the P0674 code still continues to flash on the system.

Step 2: Disconnect

Disconnect the connectors connecting the glow plugs in the 4th cylinder to the network of modules. Then switch to Ohm’s mode on the DVOM. This mode will allow you to read the Ohm rating each second electric current passes through the wires of the glowplug.

Step 3: Read Meter and Adjust Accordingly

You can connect one to the wires if there are no pre-existing Ohmmeters. Then check the readings on the meter. The glowplug is fine if the reading is between 0.5 to 2.0 Ohms.

If the reading is slight, you might need to adjust the position. However, if the reading is too high, replace the entire glowplug network with a new one.

Step 4: Replace old worn out fuse and wires

Check out the surrounding wires and the connectors in the module network from the computer mainframe to the glowplugs.

If they appear torn or worn out, make sure to replace them with new ones. You can also repair them if the damage isn’t to a great extent.

Step 5: Reconnect wires

If you notice wires that have been disconnected or have come loose from their appropriate palace, you can reconnect them back. However, if the P0674 still persists, you might want to try and replace the wires with a new one entirely.

Other Symptoms Of Getting P0674 Code On Duramax

You might often notice your car having a bad outburst of fuel economy without any prior warning. Usually, this problem can be attributed to many external factors, including the wrong oil type.

However, the possibility of faulty glowplugs causing this issue isn’t unaccountable, aside from bad fuel economy. As pointed out below, plenty of other symptoms could be associated with the P0674 code.

  • Misfiring Engine
  • Low acceleration or throttled engine performance
  • Issues with a standard transmission
  • The exhaust can release black fumes
  • More C02 emissions compared to regular emissions
  • Rough idling

How Much Does It Cost To Fix Duramax P0674 Code?

If you fix the P0674 code, there is a high chance that you might have to replace old worn-out glowplugs with new ones.

Each glowplug does not have a high individual price margin and can cost as low as 15 USD. To replace all older glow plugs, you will need to pay a total of 120 to 270 USD depending on the model of your engine.

In addition to the cost of buying the glowplugs, you might also require to spend an extra 50 USD for auxiliary items and components, including wires.

Finally, if you hire an outside mechanic, you might need to pay an extra 100 USD as the labor charge.

Of course, the labor cost you will be paying might differ from ours since different mechanics will ask for different prices depending on their payment policies. However, anything above 100 USD will be too much to fix these P0674 code-related issues.

Can You Drive Your Duramax With Code P0674?

You definitely can drive your Duramax while the code persists. However, we would advise you against doing so.

P0674 can be a very problematic issue that doesn’t require much of a technical solution. Simply replacing the glowplugs should fix it. However, if you are going to drive without addressing the issue, this could be harmful to your vehicle in the long run.

Not only do faulty glowplugs cause low fuel efficiency, but they can also cause the depreciation of your vehicle’s engine in the long run. As such, you are more than advised to fix the issue as per the code as soon as possible.


Each year there are approximately 1.3 million deaths caused by road accidents in the world. As such, the Duramax you will drive must be at the top of its performance.

If your vehicle is showing the indications of the P0674 code, you shouldn’t delay fixing it. You can even choose to use the step-by-step procedure we have mentioned above.

Of course, f you do not have the time, you are more than welcome to hire a professional. However, never delay solving the issue for too long. With these issues persisting, your Duramax is more prone to potential accidents than when there are none of these problems.

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