DTC P0381 Glow Plug/Heater Indicator Circuit Malfunction

Welcome to this informative blog post dedicated to resolving On-Board Diagnostic Trouble Code P0381: Glow Plug/Heater Indicator Circuit Malfunction. As an Automotive Enthusiast and a Certified Automotive Technician, my mission is to provide you with valuable insights and practical guidance for effectively addressing automotive issues. In the following sections, we will decode the meaning of DTC P0381, explore its associated symptoms, identify potential causes, outline diagnostic procedures, and discuss effective strategies for resolving this problem.

1. What does P0381 code mean?

Let’s start by unraveling the significance of DTC P0381. Within the realm of automotive diagnostics, “P0381” is a standardized code used by your vehicle’s onboard computer (OBD-II system) to indicate a specific issue. The “P” designates it as a Powertrain-related problem, often linked to the engine or transmission. In this case, “0381” points to a Glow Plug/Heater Indicator Circuit Malfunction.

In simpler terms, DTC P0381 serves as an alert that there is a problem within the Glow Plug/Heater Indicator Circuit. This circuit is crucial for monitoring and controlling the operation of the glow plugs, which are essential for efficient diesel engine startup, particularly in cold conditions.

2. What are the causes of DTC P0381?

Now, let’s explore the potential causes behind DTC P0381:

  • Faulty Glow Plug/Heater Indicator: The indicator itself may be malfunctioning, preventing it from accurately monitoring the glow plug operation.
  • Wiring or Connector Issues: Damaged, corroded, or loose wiring and connectors within the indicator circuit can disrupt the flow of electrical signals.
  • Glow Plug/Heater Relay Problems: The relay responsible for controlling the glow plug/heater operation may be faulty.
  • Faulty Glow Plugs: In some cases, defective glow plugs can trigger this code as they may not provide the expected feedback to the indicator.
  • Battery Voltage Issues: Insufficient voltage from the vehicle’s battery can impact the glow plug/heater circuit’s performance.

3. What are the symptoms of DTC P0381?

Recognizing the symptoms associated with this trouble code is crucial for diagnosis. Common signs of DTC P0381 may include:

  • Check Engine Light (CEL): The most noticeable indicator is the illumination of the check engine light on your dashboard.
  • Difficulty Starting: You may experience difficulty starting your diesel engine, particularly in colder weather, as the glow plug/heater circuit may not operate optimally.
  • Rough Engine Idle: A malfunctioning indicator circuit can result in a rough or unstable engine idle.
  • Reduced Fuel Efficiency: A compromised glow plug/heater circuit can lead to decreased fuel efficiency as the engine struggles to start efficiently.

4. How to diagnose DTC P0381?

Diagnosing DTC P0381 requires a systematic approach. Here’s a step-by-step guide:

  • Code Scanning: Utilize an OBD-II scanner to retrieve the trouble code and confirm the issue.
  • Inspect Glow Plug/Heater Indicator: Examine the indicator itself for any visible signs of damage or malfunction.
  • Check Wiring and Connectors: Thoroughly inspect the wiring and connectors related to the indicator circuit for any damage, corrosion, or loose connections.
  • Test Glow Plug/Heater Relay: Evaluate the performance of the glow plug/heater relay to ensure it’s functioning correctly.
  • Verify Battery Voltage: Confirm that the vehicle’s battery is providing sufficient voltage for the glow plug/heater circuit.

5. How to fix DTC P0381 problem?

Now, let’s explore effective strategies for fixing DTC P0381:

  1. Replace Faulty Indicator: If the indicator itself is malfunctioning, replace it with a compatible indicator unit.
  2. Repair or Replace Wiring and Connectors: Address any damaged wiring or connectors in the indicator circuit, repairing or replacing them as necessary.
  3. Glow Plug/Heater Relay Replacement: If the relay is faulty, replace it with a suitable relay to control the glow plug/heater operation.
  4. Ensure Battery Voltage: Verify that the vehicle’s battery is in good condition and providing the necessary voltage for the indicator circuit.
  5. Clear the Trouble Code: After completing the repairs, use your OBD-II scanner to clear the trouble code.
  6. Test Glow Plug/Heater Operation: Attempt to start your diesel engine to confirm that the glow plug/heater circuit is functioning correctly, and the check engine light remains off.


In conclusion, DTC P0381, indicating Glow Plug/Heater Indicator Circuit Malfunction, can be effectively addressed with the knowledge and guidance provided in this article. Prioritize safety and, when in doubt, seek professional assistance to ensure your diesel engine starts smoothly, especially in challenging weather conditions. Happy troubleshooting on your automotive journey!