Glow plugs are mainly used to heat the air-fuel mixture to complete combustion.
A P0380 error code is generated in the OBD-II scanner when the glow plugs malfunction.
The problem usually happens during the cold start and affects engine performance.
As a result, understanding the P0380 error code and how to resolve it is important.
In this article, I have explained the meaning of the P0380 error code, its symptoms, potential causes, and fixing methods in detail.
What is P0380 Code
The P0380 code is a diagnostic trouble code generated by an OBD-II scanner.
The P0380 code primarily indicates a malfunction of the glow plug or heater circuit A.
A glow plug heats the air-fuel mixture during the combustion process when the diesel engine is started.
P0380 error code is generated when the PCM, or Powertrain Control Module, detects a problem with the glow plug or its associated circuit.
The P0380 error code reduces engine performance and makes starting the engine harder.
Symptoms of P0380 Code
The P0380 code is triggered when the glow plugs malfunction.
Therefore, you may notice following 5 common symptoms:
- Having difficulty starting the engine, especially on cold starts.
- Engine rough idle
- Check engine light illuminates
- Reduced engine performance and power
- Increased exhaust emissions.
6 Causes of P0380 Code
The P0380 error code is caused by 6 main factors, including a faulty glow plug, a faulty glow plug timer, a faulty connector, a glitch with the glow plug control module, an electrical problem, and a problem with the PCM.
1. Faulty Glow Plugs
An engine usually has one glow plug per cylinder.
Over time, glow plug heating elements deteriorate and cause inefficient heating during cold starts.
As a result, the P0380 code appears on the OBD scanner to let you know that the glow plug has become faulty.
2. Faulty Glow Plug Timer
A glow plug timer controls the glow plug and ensures proper heating timing.
When the timer completes its cycle, the engine can be started.
But if the glow plug timer is faulty, it fails to control glow plugs properly and causes a P0380 error code.
3. Faulty Connector
If the wiring connectors are loose or damaged, it disrupts the electricity flow and triggers the P0380 code.
4. Problems with the Glow Plug Control Module
The glow plug control module is responsible for controlling the glow plug’s functions.
A faulty control module can prevent proper voltage delivery to the glow plug, resulting in the P0380 code.
5. Electrical Issues
In some cases, all components work normally, but blown fuses or issues with the glow plug relay circuits are to blame for the P0380 error code.
6. PCM Malfunction
The Powertrain Control Module is primarily responsible for controlling and monitoring glow plugs.
If there is a problem with the PCM, it could result in the P0380 error code.
However, the P0380 code is extremely rare due to PCM malfunctions.
How to Fix P0380 Duramax [A Complete 6 Steps Guide]
Glow plugs are vital for a vehicle, especially during cold starts.
P0380 error code indicates a problem with glow plugs.
Therefore, you must take the necessary steps if you see the P0380 code in the OBD scanner.
A systematic approach is required to identify and resolve the underlying issue with the glow plug or heater circuit to fix the P0380 Duramax error code.
Follow the steps below to fix the P0380 Duramax error code:
1. Perform a Visual Inspection
Inspect the glow plugs, connectors, and wiring in the glow plug.
If you find any damage, loose connections, or corrosion, it is necessary to repair or replace the faulty parts to resolve the problem.
2. Check Glow Plug Resistance
Now use a digital multimeter to measure each glow plug’s resistance.
If any of the glow plug’s resistance is mismatched with the manufacturer’s specifications, replace it.
3. Check the Glow Plug Voltage
Use a multimeter to check the glow plug voltage.
Check the glow plug module voltage first, then check each plug’s connector.
The voltage should be within the specification range.
A glow plug can also be tested by applying 12 volts to each terminal and ground body for 2-4 seconds.
If the glow plug is in good condition, it should be red hot.
In other words, whether the glow plug is light red or not red, it is not in good condition.
4. Check the Glow Plug Control Module
Inspect the glow plug control module properly.
If the glow plug control module is faulty, replace it.
Inspecting the glow plug control module requires advanced scanner tools like the OBD-II scanner.
Therefore, you have to take your vehicle to a repair shop for an advanced diagnosis.
5. Inspect the PCM
If everything appears to be in order, but the P0380 code persists, you should investigate the functionality of the vehicle’s Powertrain Control Module, or PCM.
An experienced auto mechanic can perform the inspection properly.
So take your vehicle to a qualified technician.
In general, PCM malfunctions are rare, but if they do happen, they’re expensive to repair.
6. Reset the Error Code
After replacing the faulty components, reset the P0380 error code.
You can reset the error code by using a diagnostic scanner or by disconnecting the negative battery cable for 10 seconds.
Now reconnect the battery cable and test the vehicle.
Ensure the P0380 code doesn’t reappear again and that the glow plug works appropriately.
You can watch the video to watch the whole process visually.
Preventive Measures for P0380 Code
Follow these 7 steps below to keep the glow plug in perfect condition and avoid the P0380 code:
- Ensure regular maintenance according to the manufacturer’s recommendation to keep the glow plugs in working condition.
- Ensure that the newer glow plug is of good quality when replacing a faulty one.
- Try to avoid frequent cold starts as much as possible.
- Park your vehicle in a warmer place or use block heaters to reduce the strain on the glow plugs.
- Wait a few minutes before driving to allow your combustion chamber to warm up properly.
- Inspect and clean the wiring harness and glow plug connections periodically.
- Use high-quality fuel to improve combustion efficiency and reduce deposits on glow plugs.
If you follow the instructions above, the glow plug will function properly, and you will be able to prevent the P0380 error code from appearing.
How Much Does It Cost to Fix P0380 Code Duramax?
The cost of fixing the P0380 code depends on the problem.
Generally, the P0380 error code costs around $60 to $250 to fix.
When the problem is severe, the repair costs occasionally exceed the acceptance, but this is a rare occurrence.
Can you run a Duramax with a bad glow plug?
Yes, you can run a Duramax safely with a glow plug warning light if you can start the vehicle easily.
But remember, every warning light or error code indicates something is wrong with your vehicle and needs treatment.
So, take the glow plug problem seriously and fix it before it get worse.
What happens if you start a diesel without waiting for glow plugs?
You should always give your engine time to warm up properly before driving.
Starting a diesel engine without first allowing the glow plugs to warm up properly may result in a number of issues later on.
Should I change all glow plugs at the same time?
Yes, you should replace all glow plugs at the same time, even if they are not malfunctioning.
The same thing should be done in the case of faulty spark plugs.
This is because all the glow plugs are the same age, so if one is malfunctioning, the others will start malfunctioning soon.
Therefore, you should replace all the glow plugs at the same time.
How long do glow plugs last in a Duramax?
Generally, Duramax glow plugs can last around 100,000 miles.
However, they will fail sooner if you frequently use hard-starting or lower-quality glow plugs than the manufacturer’s recommendation.
Now you know the potential causes of the P0380 code and how to resolve it.
It is easy to resolve this error code, and the repair cost is relatively low.
So, don’t ignore the problem and take the necessary steps if you experience P0380 code symptoms.
Hire an experienced mechanic if you can’t fix the problem yourself.