chcvy lml engine problems

LML Duramax Problems (Common Things that Fail)

The lml Duramax diesel engine is one of the best diesel engines ever made. Why? It depends on who you ask. Most people would say it’s because of the mass amount of torque and horsepower these engines produce.

Some would also say it is their dependability, durability, and great fuel economy. But like many things in life, there are some problems with this engine too.

In short, the most common lml Duramax problems are Injector Failure, Turbo Failure, Heat-Related Issues, Leaky EGR Cooler, Exhaust Back Pressure Valve Failure, Air Conditioning Failure, DEF System Issues, Leaky Fuel Lines & Fittings, and EVAP System Leaks.

Is LML Duramax Engine Good?

The LML Duramax is a great engine. It is powerful, efficient, and durable. The LML is the most powerful Duramax engine ever produced.

The LML was first introduced in the 2011 model year GMC and Chevy HD trucks. This generation of the Duramax is still in production for Chevrolet and GMC pickups, but in 2017 the L5P Duramax became the newest version.

Even though the LML has been around for a while and there are several issues to watch out for, it is still a reliable engine that can last upwards of 300,000 miles with proper maintenance and care.

LML Duramax Issues

The Duramax engines are no stranger to problems. It has had its fair share of issues since its introduction in 2001, and it seems to be a common theme that the earlier versions are more prone to failure than the newer versions.

The LML Duramax engine is no different. Though it has undergone several modifications since its introduction, many of the same problems that plagued the earlier version still persist today. Here are some of the most common problems with the LML Duramax:

  • Injector Failure
  • Turbo Failure
  • Heat-Related Issues
  • Leaky EGR Cooler
  • Exhaust Back Pressure Valve Failure
  • Air Conditioning Failure
  • DEF System Issues
  • Leaky Fuel Lines & Fittings
  • EVAP System Leaks

How many miles will a LML Duramax last?

The answer to this is complicated. It depends on how you maintain it. Like most diesel engines, it should last for 200,000-300,000 miles if it is well maintained. Like any other engine, the Duramax will last as long as you want it to.

It all depends on how well you maintain and care for it. Also, how much maintenance varies from truck to truck and is dependent on how hard you run your truck. Also, the biggest indicators that a diesel truck will go 200,000 to 300,000 miles are the fuel economy and the quality of the engine.

LML Duramax Pros and Cons

Here are some pros and cons to help you decide how this might be the right engine for you:


  1. the 6.6 liter Duramax is an amazing engine and my favorite diesel engine of all time
  2. the LML Duramax is a very reliable truck when maintained properly
  3. it is one of the fastest trucks out there for towing and off roading
  4. they’re very easy to drive and handle well
  5. they’re very fuel-efficient (for a diesel) and can tow heavy loads with ease.


  1.  these trucks are not exactly cheap  they need to be upgraded a little before getting into heavy-duty pulling or racing
  2. they’re not exactly the best-looking truck out there
  3. if you have kids, it might be hard to find seats that will fit them
  4. These trucks don’t come with many stock accessories like other trucks do

How common is CP4 failure LML?

The CP4 is one of the most problematic parts in the LML Duramax. The main reason for its failure is that it simply can’t handle the amount of pressure that the engine produces.

People often mistake fuel injectors for a common cause of this failure, but these are just two different manifestations of the same issue: too much fuel pressure builds up in the head, leading to leaks and ultimately to catastrophic damage.

CP4 failures are most common in late ‘08 and early ‘09 trucks, but they’re also starting to appear in the ‘10s and even some ‘11s. We don’t know exactly how many trucks have experienced CP4 failures, but we’ve seen a lot of them come through our shop over the past couple of years


The only way to get the most from your diesel engine is with serious maintenance, and lml duramax issues can crop up quickly if you don’t keep your eye on their performance.



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