DTC P0382 Glow Plug/Heater Circuit “B” Malfunction

Troubleshoot On-Board Diagnostic Trouble Code P0382: Glow Plug/Heater Circuit “B” Malfunction.

Welcome to this comprehensive blog post aimed at helping you address On-Board Diagnostic Trouble Code P0382: Glow Plug/Heater Circuit “B” Malfunction. As an Automotive Enthusiast and a Certified Automotive Technician, I’m here to provide you with valuable insights and step-by-step guidance to effectively tackle automotive issues. In the sections that follow, we will decode the meaning of DTC P0382, explore its associated symptoms, uncover potential causes, outline diagnostic procedures, and discuss effective strategies for resolving this problem.

1. What does P0382 code mean?

Let’s begin by demystifying the significance of DTC P0382. Within the realm of automotive diagnostics, “P0382” is a standardized code used by your vehicle’s onboard computer (OBD-II system) to flag a specific issue. The “P” designates it as a Powertrain-related problem, often related to the engine or transmission. In this case, “0382” indicates Glow Plug/Heater Circuit “B” Malfunction.

To put it simply, DTC P0382 serves as an alert that there is an issue within the Glow Plug or Heater Circuit “B.” This circuit is crucial for starting diesel engines, especially in cold weather, as it preheats the air in the cylinders for efficient ignition.

2. What are the causes of DTC P0382?

Now, let’s delve into the potential causes behind DTC P0382:

  • Faulty Glow Plug(s): One or more glow plugs in Circuit “B” may be malfunctioning or burnt out.
  • Wiring or Connector Problems: Damaged, corroded, or loose wiring and connectors in the circuit can disrupt the flow of electrical current.
  • Glow Plug Relay Issues: The relay responsible for controlling the glow plug operation may be faulty.
  • Battery Voltage Problems: Insufficient voltage from the vehicle’s battery can impact the glow plug’s performance.
  • Engine Control Module (ECM) Problems: Rarely, issues with the ECM can result in this code.

3. What are the symptoms of DTC P0382?

Recognizing the symptoms associated with this trouble code is essential for diagnosis. Common signs of DTC P0382 may include:

  • Difficulty Starting: Your diesel engine may have trouble starting, especially in cold weather, as the glow plug circuit’s malfunction affects the preheating process.
  • Check Engine Light (CEL): The most noticeable indicator is the illumination of the check engine light on your dashboard.
  • Rough Engine Idle: If the glow plug circuit isn’t functioning correctly, you may experience a rough or unstable engine idle.
  • Reduced Fuel Efficiency: A malfunctioning glow plug circuit can lead to decreased fuel efficiency as the engine struggles to start efficiently.

4. How to diagnose DTC P0382?

Diagnosing DTC P0382 involves a systematic approach. Here’s a step-by-step guide:

  • Scan the Code: Use an OBD-II scanner to retrieve the trouble code and confirm the issue.
  • Inspect Glow Plugs: Check the condition of the glow plugs in Circuit “B.” Replace any faulty ones.
  • Examine Wiring and Connectors: Thoroughly inspect the wiring and connectors related to the glow plug circuit for damage, corrosion, or loose connections.
  • Test the Glow Plug Relay: Evaluate the performance of the glow plug relay to ensure it’s functioning correctly.
  • Check Battery Voltage: Verify that the vehicle’s battery is providing sufficient voltage for the glow plug operation.

5. How to fix DTC P0382 problem?

Now, let’s explore effective strategies for fixing DTC P0382:

  1. Replace Faulty Glow Plugs: If any glow plugs are defective, replace them with high-quality replacements suitable for your diesel engine.
  2. Repair or Replace Wiring and Connectors: Address any damaged wiring or connectors in the glow plug circuit, repairing or replacing them as needed.
  3. Glow Plug Relay Replacement: If the relay is faulty, replace it with a compatible relay to control the glow plug operation.
  4. Battery Voltage Maintenance: Ensure that the vehicle’s battery is in good condition and providing the necessary voltage for the glow plug circuit.
  5. Clear the Trouble Code: After completing the repairs, use your OBD-II scanner to clear the trouble code.
  6. Test Start: Attempt to start your diesel engine to confirm that the issue has been successfully resolved, and the check engine light remains off.


In conclusion, DTC P0382, indicating Glow Plug/Heater Circuit “B” Malfunction, can be effectively addressed with the knowledge and guidance provided in this article. Always prioritize safety and, when in doubt, seek professional assistance to ensure your diesel engine operates optimally, especially in challenging weather conditions. Happy troubleshooting on your automotive journey!