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P0380 OBD-II Trouble Code: Glow Plug/Heater Circuit “A” Malfunction

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P0380 code definition

The P0380 trouble code notes an issue with the glow plug heater circuit A.

What the P0380 code means

The P0380 code is a standard OBD-II trouble code suggesting an issue within the glow plug heater circuit. When the powertrain control module (PCM) detects a variation in the voltage from the “A” area of the glow plug heater circuit that is more than a 10 percent variation from the expected output, the P0380 code will be detected. This code is associated with numerous other glow plug trouble codes.

What causes the P0380 code?

Many things can trigger the P0380 code. Some of the more common issues include:

  • Malfunctioning glow plug or relay
  • Faulty glow plug timer
  • Faulty glow plug module
  • Blown fuse in the circuit
  • Faulty wiring and electrical connectors, such as corroded connectors or open wiring

What are the symptoms of the P0380 code?

When the P0380 trouble code is triggered, it will likely be accompanied by the check engine soon Warning Light, as well as the globe plug indicator Warning Light. The vehicle also may have a difficult time starting, may be excessively noisy during start-up, and may produce white exhaust smoke.

How does a mechanic diagnose the P0380 code?

The P0380 code will be diagnosed using a standard OBD-II trouble code scanner. A professional mechanic will use the scanner to observe the freeze frame data. Using the freeze frame data, the mechanic can learn more about the P0380 code, and search for additional codes (it is common for the P0380 code to be accompanied by other glow plug trouble codes). The technician will then reset the trouble codes and restart the vehicle, to see if the codes return. If the codes do not return, it is assumed that they are intermittent and that the glow plug heater circuit is in working order.

If the P0380 code returns, the mechanic should inspect the wires, connectors, and fuses around the glow plug heater circuit. Any loose or open wires, corroded or damaged connectors, or blown fuses should be replaced. Following replacement, the trouble codes should once again be reset, and the vehicle restarted, to see if the issue has been resolved. If it has not, the mechanic will remove the glow plug in the A area and test it, as well as the relay. If needed, the components will be replaced, and all remaining trouble codes should be addressed as well.

Common mistakes when diagnosing the P0380 code

The most common mistake when diagnosing the P0380 code comes from a failure to properly follow the OBD-II trouble code diagnosis protocol. Mechanics should always follow the proper protocol in order, which includes addressing numerous trouble codes in the order in which they appear.

Failure to follow the proper protocol can also result in the glow plug or relay being replaced when the wires, connectors, or fuses were the actual issue.

How serious is the P0380 code?

A detected P0380 code is unlikely to render a vehicle as unable to operate, but it will keep the engine from running properly.

What repairs can fix the P0380 code?

The most common repairs for the P0380 trouble code include:

  • Replacement of a glow plug or glow plug relay
  • Replacement of heater circuit wires, connectors, and fuses
  • Replacement of glow plug timer or module

Additional comments for consideration regarding the P0380 code

While blown fuses in the glow plug heater circuit are commonly associated with the P0380 code, they are usually the result of a deeper issue. If a blown fuse is detected, it should be replaced, but it shouldn’t be assumed to be the only issue or the cause of the P0380 trouble code.

Need help with a P0380 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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