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P0382 OBD-II Trouble Code: Glow Plug / Heater Circuit "B" Malfunction

check engine light

P0382 code definition

The P0382 code being stored by a vehicle’s PCM means that the glow plug for a diesel engine has malfunctioned.

What the P0382 code means

Diesel engines don’t just consume a different type of fuel than the kind necessary for more conventional vehicles. They actually function a lot differently too. One example of this is the need for a glow plug. When an owner goes to start their diesel engine, the PCM (Powertrain Control Module) immediately takes a reading on the temperature of the engine.

If it finds that the temperature is too low, a glow plug is used to heat up the cylinder temperatures so that the diesel fuel will have an easier time igniting. These glow plugs will literally glow red hot in order to achieve the needed temperature for this to happen.

In some vehicles, the PCM will actually keep the glow plugs going after the engine has started. Manufacturers elect for this option when they want to reduce engine noises or simply the production of white noise.

When the P0382 code is stored by the PCM, it’s because it’s detected a problem with the glow plug heater circuit B which is keeping it from working properly.

What causes the P0382 code?

There are four main reasons that could cause this problem to occur. They are:

  • An open fuse
  • A faulty glow plug
  • A problem with the glow plug’s wiring (it’s open, damaged, short to ground, etc.)
  • The glow plug relay isn’t working correctly

In very rare cases, the PCM may actually be the thing that is faulty. Don’t go about trying to repair or replace it, though, until you’ve exhausted every other option.

What are the symptoms of the P0382 code?

Generally, if this trouble code is logged, the driver should see their check engine light come on. Other reliable signs would be:

  • The MIL (Malfunction Indicator Lamp) light comes on
  • The glow plug indicator – it’s the “Wait to Start” indicator in some vehicles – stays on longer than normal
  • It’s tough to start the vehicle in cold weather

This last one is the most common indicator. You may experience one or both of the other two too, but if your vehicle is easy to start, it’s probably not a P0382 problem.

How does a mechanic diagnose the P0382 code?

If a mechanic is working on a vehicle with a P0382 code logged, they will most likely follow this path to a resolution:

  • Use their OBD-II scanner to find out all the codes that have been stored by the vehicle’s PCM
  • Try starting the vehicle to see if it’s difficult and/or if they can reproduce the problem
  • Check all fuses to see if any are blown
  • Test the relay for the glow plug

As the problem always involves the glow plug, simply tracing the steps between it and the starter is usually enough to find the problem.

Common mistakes when diagnosing the P0382 code

The glow plug is no doubt important to finding the source of the P0382 code, but don’t just stop there. For example, you may notice there’s an issue with the relay. Address that, but continue your search for any other potential problems, especially if there were related codes found when the OBD-II scanner was used.

How serious is the P0382 code?

This isn’t the type of problem that will cause you to end up off the road, but it will keep you from getting on the road in the first place. If you live in a cold environment, a P0382 problem could mean your car stays still for a very long time.

What repairs can fix the P0382 code?

Some kind of replacement will almost surely be necessary. Whether it’s the glow plug itself, the wiring, connectors, etc. something is going to get changed out.

Additional comments for consideration regarding the P0382 code

Related codes like P0380, P0381, P0383 and P0384 are commonly present along with this one.

Need help with a P0382 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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