06 Must Know L5P Duramax Problems [+Solutions]

Duramax L5P engine is used in Chevrolet Silverado and GMC Sierra 2500/3500 HD models.

Duramax L5P is the successor of LML.

But it offers much more than Duramax LML.

But no vehicles are perfect.

It has some minor problems that can be overlooked.

L5P Duramax Problems [06 Problems with Solutions]

Duramax L5P has 6 minor problems, including a faulty fuel injector, faulty TMAP sensor, bad turbocharger, antenna leaking, coolant sensor, and poor paint quality.

Let’s discuss these problems with solutions elaborately.

1. Fuel Injector Failure

2018 duramax l5p problems

The fuel injector of Duramax L5P lets more fuel inside the cylinder than standard.

It’s a very common issue for the L5P.

There are 8 injectors. You need to find out which injectors are bad and replace them.

In most cases, injectors 5 and 2 are the main culprit.

4 most common symptoms of a bad fuel injector of L5P are-

  • White smoke coming out of the exhaust
  • Knocking sound from the engine
  • Code P0204
  • Code P0300

When injectors fail badly, your vehicle will go to Limp Mode, with a code on your dashboard.

If any of these code pops up on your screen, then be sure it’s due to a bad fuel injector.

To learn more about bad fuel injectors and turbochargers, watch this video.


Find the bad injectors by diagnosis and replace the bad injectors with new ones.

As a mechanic, I recommend changing all 8 injectors if any of the 4 symptoms are seen.

2. TMAP Sensor Failure

2019 duramax l5p problems

TMAP sensor provides temperature and manifold pressure information to the ECM.

After driving 30000 miles or less, soot and dirt gather around the TMAP sensor, which gets faulty.

Symptoms of a faulty TMAP sensor-

  • P00C7 code
  • P0106 code

A faulty MAP sensor provides wrong information to the ECM.

These codes will pop up if the TMAP sensor is defective.


You need to clean the TMAP sensor with the MAP sensor cleaner.

The cleaner costs around 5 Bucks.

Disconnect the battery terminals while cleaning the MAP sensor, or a code will pop up.

Keep extra MAP sensor.

It only cost around 18 Bucks.

Keep in mind sensors are very sensitive.

So, GM doesn’t recommend cleaning the sensors with water or cleaner.

Clean at your own risk.

My advice is to replace them cause it doesn’t cost much.

3. Turbocharger Issue

2021 l5p duramax problems

Duramax L5P has a Variable Geometry Turbocharger (VGT).

The exhaust housing of the VGT turbocharger has veins and changes its position.

When they change their position, they increase or decrease the boost pressure.

After driving 30000 miles, the turbocharger’s compressor fails to function properly.

There will be no indication of turbocharger failure until it fails completely.


You must check the turbocharger and replace it if the function of the VGT turbocharger is compromised.

Otherwise, it will cause major damage to the engine.

4. Leaking Antenna

Leaking Antenna

2017 models have water-leaking antenna issues.

Dampening comes through the visor and antenna.

GM has fixed the visor issue in the 2018 models.

So, only 2017 L5P owners’ have antenna leakage issues.

It’s a common issue with most GM trucks.


Take your vehicle to the dealer.

They will charge 38 Bucks and fix the issue permanently.

5. Faulty Coolant Sensor

Faulty Coolant Sensor

Whether you own a new or old 2017/2018 Duramax L5P, the coolant sensor is faulty.

It will give you a false warning on your dashboard during the winter.

But in the summer, you won’t have to face any issues with the coolant sensor.

False cooler warning often pops up.

If you don’t pay heed to the warning light, it’s not a big issue.

Some users also reported coolant leakage in 50000 miles which is uncommon.

So, you need to check the coolant sensor and the leakage.

Fix it before it becomes a headache.


Replace the coolant sensor or ignore the false coolant code.

It’s not a big deal.

6. Poor Paint Quality

The quality of the paint of Duramax L5P is not up to the mark.

With the truck getting older, the paints become a little bit dull.

After every wash, you will notice swirl marks or little circles on the surface of the body of your truck.

Swirl marking is a big issue that will make your vehicle look older.

2016 or previous models of Duramax don’t have this issue.


You can repaint your truck, but it will cost you a lot of money.

Painting again is not necessary.

Just ignore the issue.

When your truck gets older, paint the vehicle with good quality paint which doesn’t have a swirl issue.

What is the L5P Duramax Life Expectancy?

Duramax L5P will last around 500000 miles or above.

It depends on the maintenance.

Every vehicle needs basic maintenance, including changing engine oil every 5000 miles, changing tires, replacing brake pads, adding DEF, adding coolant, changing the air filter every 15000 miles, etc.

Diagnosing your truck every 50000 miles and replacing faulty or damaged parts is basic and compulsory maintenance.

Many L5P owners neglect maintenance.

As a result, their vehicle doesn’t last long.

On the other hand, many vehicle owners maintain their vehicles properly, and their L5P last more than 500000 miles.

Is L5P Duramax Reliable?

Yes. It’s not only reliable, but it’s also one of the best pickup trucks in the USA presently.

It’s a durable and well-built pickup truck that can last up to 500000 miles or above without any major issues.

You can rely on L5P for a better and longer service.

It won’t disappoint you.

Final Thoughts

These minor problems can be overlooked cause every vehicle has some issues.

Overall, Duramax L5P is one of the best pickup trucks in the American market.

So, without any doubt, you can go for it.

Leave a Comment