How to Fix the P0380 DTC Code on Duramax (Expert Approach)

If you’re a Duramax diesel truck owner and a road veteran, you’ve probably seen your fair share of Diagnostic Trouble Codes (DTCs). Despite adding to your headache, they are still a necessary evil of modern driving, helping you determine the problem with your car and how to deal with it.

The P0380 code on Duramax is associated with malfunctions within your truck’s glow plug heater circuit ‘A.’ Various circumstances may lead to this code, but it most frequently occurs due to a faulty glow plug relay.

Now, if you’re seeing this code on your Duramax, don’t panic just yet. This troubleshooting guide covers the details of the P0380 code, common problems that cause it to appear, what you can do about it, and associated costs.

How to Fix the P0380 DTC Code on Duramax

What Does P0380 Code Mean On Duramax?

The P0380 is a generic transmission code on Duramax diesel trucks or any vehicle made after 1996. This code means that the vehicle’s glow plug heater circuit ‘A’ is malfunctioning.

When you start your truck, the power control module makes sure the diesel engine is warm enough to run. If it’s not, the computers make it hotter by activating the glow plugs to burn the fuel quickly.

And when it doesn’t get a proper response from the glow plug circuit ‘A,’ it displays the P0380 code, illuminating the check light. Here’s a breakdown of what the code has to do with this problem.

  • P = Powertrain, the system of components that propels your car forward.
  • 0 = a generic number derived from the SAE standard
  • 3 = Ignition system
  • 80 = Specific fault index (In our case, this denotes glow plug heater circuit ‘A’)

How Serious Is P0380 Code on Duramax?

In most cases, detecting a P0380 code will not make a vehicle unusable, but it will cause the engine performance to suffer. When the glow plug heater circuit malfunctions, it can cause your engine to stall during initial start-up or while driving down the highway.

This code is serious enough to take note of, but it’s not an immediate threat to your safety. However, things can worsen faster if you aren’t careful enough to avoid hard starts or extended idling. For instance, it can render your control module inoperable.

What Are The Symptoms of the P0380 Code on Duramax?

The MIL (Malfunction Indicator Lamp) or glow plug light coming on is a telling sign of the P0380 code popping up. Other symptoms include-

  • The Glow plug or Start-up standby light keeps illuminating for a prolonged period or may stay on.
  • A hard-to-start engine, particularly during cold weather.
  • Noisy start and shifting.
  • White smoke emission from the exhaust.

What Causes P0380 Code on Duramax?

Several reasons can lead the P0380 code to trigger the check engine light on your dash. The most common reason is a faulty glow plug relay. A loose or corroded connector may also lead to the P0380 code appearing. Other potential causes include-

  • A blown fuse in the glow plug circuit.
  • Bad glow plugs, heater elements, or control modules.
  • An open or shorted glow plug circuit.
  • A malfunctioning glow plug timer.

How to Fix P0380 Code on Duramax?

Trying to fix a P0380 code can be frustrating if you don’t know how to test the glow plugs, the relay, the control unit, and the wiring harness. You’re best off leaving the job to a professional. Yet, if you have hands-on experience doing automobile repairs, you can try it out yourself.

A basic OBD-II code reader is required to diagnose the P0380 DTC on Duramax, as with most others. Once you have it, proceed with the troubleshooting steps.

Step-1: Obtain the Freeze Frame Data

Whenever your truck’s computer sets a code, it also saves a “freeze frame data.” It shows the conditions at the exact moment the code was set, which is necessary to diagnose the issue. To retrieve this data, use an OBD-II code reader.

Step-2: Check the Glow Plug Relay

The glow plug relay is one of the most common causes of the P0380 code on Duramax trucks. Start by checking whether there’s any voltage on the control side of the relay using a multimeter. If there’s no voltage, the problem may be with an open fuse or a bad connection to the powertrain control module.

Step-3:  Test the Glow Plugs

Once you’ve verified that the relay is getting power, it’s time to test the glow plugs themselves. You’ll need a 12-volt test light and a helper to do this. Have your helper crank the engine while you check each glow plug with the test light. If the light doesn’t come on, the glow plug is bad and must be replaced.

Step-4: Check for Shorts and Grounds

Even if the glow plugs are working, there could still be a problem with the wiring. To check for shorts and grounds, test the continuity of the wires from the glow plugs to the relay using a multimeter. If there are any breaks in the continuity, you’ll need to replace the wires.

Step-5: Replace the Glow Plug Relay

If you’ve checked all of the above and still can’t seem to fix the P0380 code, then it’s time to replace the glow plug relay. This is a relatively easy job that most people can do themselves. You’ll want to ensure you have the correct relay for your truck and follow the instructions in your repair manual.

Step-6: Check the Glow Plug Control Module

In some cases, the problem may be with the glow plug control module. This is a more complicated fix, so it’s best to leave it to a professional.

How Much Does it Cost to Fix Duramax P0380 Code?

The cost of repairing a P0380 code on Duramax can vary depending on the severity of the problem. Replacing just the glow plug relay may cost as little as $50.

However, if you have to replace the glow plugs, the price will go up. You can expect each plug to cost between $70 and $150. On the other hand, the entire glow plug control module can cost upwards of $1,000 if you must replace it too.

Then you have to consider the labor cost if you’re not DIYing, which can range from $80 to $150 per hour, depending on the complication of the repair.

Can You Drive Your Duramax With code P0380?

Yes, you can drive your truck with the P0380 code, but it’s not recommended. If the glow plugs are not working correctly, your engine may not start or misfire when cold. It’s unlikely that your truck will cease to run or shift in gear, but you may experience unexpected jolts due to the sudden misfires.

The glow plug circuit issue can also cause further damage to your engine and the harnessed parts. In the worst-case scenario, it may include the control module. So, while this issue may not pose an immediate safety threat, it’s still best to get it fixed as soon as possible.


Whether you were just looking to understand the basics or trying to find more information about how to fix the P0380 on Duramax diesel trucks, we hope this article has helped you out.

The best way to save money on repairs is to catch the problem early and fix it before it worsens. If you’re not comfortable fixing the problem yourself, take it to a professional and have them do it for you. Either way, the sooner you fix the problem, the less it will cost you in the long run.

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