Fault code P0381 – glow plug/heater indicator circuit malfunction

Fault code P0381 is called “Glow Plug/Heater Indicator Circuit Malfunction” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0381

OBD-II Trouble Code P0381 is a generic code that is defined as “glow plug indicator circuit failure”. It is set when the Powertrain Control Module (PCM) detects a general fault or failure. Which has occurred in the glow plug indicator circuit on the diesel engine.

Fault code P0381 – glow plug/heater indicator circuit malfunction

Glow plugs are used on diesel engines to provide an intense heat source. Which is necessary to provide better combustion of the fuel-air mixture when the engine is cold or the temperature is below the minimum threshold.

At low ambient temperatures, it is very difficult to ignite the diesel mixture because it may not be compressed enough to initiate combustion. Diesel engines use electrically heated glow plugs to eliminate these problems. To create a heat source in the precombustion chamber of each cylinder, to ignite the fuel-air mixture at the peak of compression.

Regardless of the ambient temperature, the glow plug control circuit will not be activated. If the engine coolant temperature exceeds a predetermined minimum threshold.

This is necessary both to extend the service life of the glow plugs and to prevent premature detonation of the fuel-air mixture.

Glow plugs are critical components of a diesel engine. Because if they fail, there is a high probability that a cold engine will not start or will start with great difficulty.

Consequently, if the circuit that controls the glow plug indicator fails, the PCM or other control module will set code P0381. A special light on the control panel may also come on.

Symptoms of vehicle malfunctions

The main signal that an error P0381 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be recorded in the memory as a malfunction).
  2. Glow plug start standby light is on longer than usual (may be on continuously).
  3. Glow plug indicator light does not illuminate.
  4. Engine may crank but not start (especially in cold weather).
  5. Possible white smoke from the exhaust pipe due to insufficient heating of fuel before combustion.

Depending on the symptoms, the error P0381 may be minor or serious. However, the problem should not be ignored, because when this error appears, the glow plug operation is likely to be disabled.

Factors that can cause this error code

The error code P0381 can mean that one or more of the following problems have occurred:

  • Glow plug indicator light is defective.
  • Faulty glow plug indicator wiring.
  • One or more glow plugs are defective.
  • Fuse or fusible link is blown.
  • Glow plug relay faulty.
  • Glow plug control module is defective.
  • Problem with the circuit board on the dashboard.
  • Sometimes faulty PCM module is the cause.

How to fix or reset OBD-2 code P0381

Some suggested steps for troubleshooting and fix the error code P0381:

  1. Read all stored data and error codes with a standard OBD-II scan tool.
  2. Clear the error codes from the computer memory and recheck the system to see if error P0381 appears again.
  3. If the error code disappears, then the problem is intermittent and there is nothing wrong with the glow plug indicator circuit.
  4. If the code appears again, visually inspect the electrical wires and connectors, as well as the fuses.
  5. Check the glow plug indicator as well as the circuit board on the dashboard.
  6. Then check the glow plugs as well as the control relay.
  7. Replace defective components if necessary.

Diagnose and repair of problems

The best place to start diagnosing error P0381 is with the Technical Service Bulletins (TSB), perhaps your problem is known and described in them. Then you should check the appropriate fuses, replace them if they are blown. Next, you should test the circuit board and glow plug indicator.

Visually inspect the glow plugs, wiring, and connectors for corrosion, bent, and loose wire contacts. Look for loose screws or nuts on the wiring connections. If necessary all defects should be repaired.

Check the connectors of the wiring harness for resistance using a digital voltmeter and compare with the manufacturer’s specifications. Do the same with the wires going to the glow plugs.

To check the glow plug itself, you must remove it, apply 12 V voltage to it, and ground the body for 2-3 seconds. If the glow plug is red hot, it is working, if it is dull red or not red at all, it must be replaced.

On which vehicles does this problem occur most frequently

Fault code P0381 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Audi
  • Dodge (RAM)
  • Ford (Excursion)
  • Hyundai (Santa Fe, Starex)
  • Isuzu
  • Kia (Sorento)
  • Mitsubishi (L200)
  • Nissan (Qashqai)
  • Opel
  • Renault (Laguna, Megane, Scenic)
  • Volkswagen

Fault code P0381 can sometimes be found with other errors. The most common are the following: P0383, P0384, P0603, P1000, P1379, P2263.

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