Codes & Diagnosis, Duramax

What Is Duramax P0380?


by Ian Nicholls


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Bad Diesel Engine Glow Plugs
Bad Diesel Engine Glow Plugs


If you own or drive a Duramax diesel truck, you’ve probably seen your fair share of P0380 code pop-ups. 

Did you know that your Duramax diesel engine may be hard to start after a cold night? However, most diesel engines have glow plugs that play an essential role in the engine’s performance, emission control, and fuel efficiency during cold starts. 

Your vehicle’s glow plug heats up the combustion chamber, so it’s easier for your vehicle to start. 

If the Power Control Module(PCM) identifies a problem in the glow plug circuit” A,” the error code p0380 shows up. Keep reading this write-up for more information about Duramax p0380, its symptoms, probable causes, and solutions. 

What Is Duramax P0380?

Duramax p0380 is a generic powertrain Diagnostic Trouble Code(DTC),  on Duramax diesel trucks and all makes or models made after 1996. It basically signifies that your vehicle’s glow plug heater circuit ‘A’ has malfunctioned.  

But wait, what exactly does this mean and what are glow plugs?

Glow plugs are heating devices that generate heat to warm your vehicle’s engine cylinder and ultimately ignite the fuel. Without the glow plugs, your diesel engine won’t start.

You see, when you start your vehicle, the Power Control Model checks the diesel engine to ensure it’s hot enough to run appropriately.

If it’s not, the computer activates the glow plugs, producing intense heat that quickly preheats and burns the diesel fuel. 

So, if the computer doesn’t get the proper response from the glow plug, that’s when the Duramax P0380 code displays, illuminating the check light. 

Almost everyone is familiar with check engine lights that sometimes display on the dashboard. If this light turns on, your vehicle’s engine computer produces a corresponding Diagnostic Trouble Code(DTC) and stores it in its memory. 

In our case, this Diagnostic Trouble Code is On-board diagnostics-II (OBD-II) for all Duramax vehicles of models 1996 and newer.

See below what this code has to do with this issue


0– A generic number derived from Society of Automotive Engineers standards. (SAE)

3-Ignition system

80-Specific fault index, in this case, indicates glow plug heater p0380 Duramax circuit’ A.’

Symptoms of Duramax P0380

When the Duramax p0380 code is triggered, it’ll be accompanied by the following symptoms.

  • Emits white smoke from the exhaust.
  • Difficulty in starting the engine, especially in cold weather and cold starts.
  • Check engine light illuminates.
  • Noisy starts and shifting.
  • Malfunction Indicator Lamp(MAL) illumination.
  • Engine misfires or a decrease in acceleration.

6 Causes of Duramax P0380 Trouble & Their Possible Solution

While several issues are associated with the Duramax P0380 code, the most common cause is a faulty glow plug relay. Here are the potential causes that can lead to the P0380 code display.

1. Fault in Glow Plug Wiring (Open, Short to Ground, Etc.)

A faulty glow plug wiring and connection can cause the entire system to malfunction. Corroded connectors, open wires, or other faulty wiring can trigger the P0380 code.


Replace the faulty glow plug wiring and connectors, especially the heater circuit wires and fuses.

2. Glow Plug Faulty

A defective glow plug may interrupt the sensitive diesel combustion process and won’t generate enough heat. Therefore, if you’re dead or have faulty glow plugs, you’ll undoubtedly face the symptoms discussed above in this article.


Although glow plugs have a long lifespan, they’re subject to wear and tear. If your glow plug has any of the symptoms mentioned above, it’s essential to replace it immediately. To check your glow plugs, follow these simple steps.

  • First, disconnect all wires from the glow plugs.
  • Secondly, hook the lip of the volt test light to the battery’s positive terminal.
  • Finally, touch the test light probe to the glow plugs terminal and check if it lights. If not, that glow plug is faulty.

3. Open Fuse

An open or blow fuse is associated with the Duramax P0380 code and requires immediate intervention. However, it’s important to note that a blown fuse may signify a deeper issue.


Check the fuses to figure out the exact problem; if you identify an open or blown fuse, repair or replace it accordingly.

4. Faulty Glow Plug Relay

Like the other vehicle parts, the glow plug relay wears out over time. Exposure to misfires, extreme temperatures, and fluctuating electrical currents can accelerate the wearing process.


In this case, you’ll need to get rid of the Duramax p0380 glow plug relay and replace it with a new one. 

I’m guessing your next question is, where is the Duramax glow plug relay location? Don’t worry; keep reading to find out. 

The Duramax glow plug relay is on the driver’s side, near the firewall, above the side valve cover.

5. Faulty Glow Plug Module

Your vehicle’s glow plug module ensures your diesel vehicle engine starts properly. Basically, it determines the electric current and timing required by the glow plugs.

If the module is faulty or malfunctions, you’ll find it challenging to start the vehicle.


Check the glow plugs, as shown in the steps above, before checking the module. To check the glow plug module, check the battery voltage of the glow plug module. If the voltage shows a drop of half a volt or more, it’s time to replace your glow plug module.

6. Issue of Power Control Module(PCM), e.g., Software Updates

The Powertrain control model is your vehicle’s brain; if it’s outdated, you will likely get the P0380 code.


To update your PCM, we recommend you contact a professional mechanic to complete this process for you.

Here Is a Step by Step Video Guide to the P0380 Duramax Fix

Winding it Up

The P0380 code is a standard Onboard diagnostic -II trouble code that signifies there is an issue within the glow plug heater circuit. 

If you have a Duramax diesel engine, it’s important to know how to identify faulty glow plugs and how they affect the performance and longevity of your vehicle. 

P0380 Duramax fix can be frustrating, especially if you don’t have the know-how and the right tools to perform the process. 

However, if you’ve got the technical know-how and hands-on experience to fix the error, we advise you to follow the manufacturer’s repair manual. If you are not comfortable fixing it by yourself, consult a professional. 

Whether you were looking for more information about the Duramax P0380 code or just wanted to understand the basics of the P0380 code, I hope this write-up was helpful. 

Ian Nicholls

Ian is a seasoned automobile enthusiast with a knack for diagnostics and repair. Adept at overseeing garage operations, skilled in troubleshooting, and passionate about ensuring top-notch vehicle performance.

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