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CP4 High Pressure Fuel Pump Failure

CLICK HERE to purchase our LML CP4 High Pressure Fuel Pump Failure Kit

The 2011-2016 Duramax suffers from a high pressure fuel pump issue unique to this year range. Failure of this CP4 pump is usually catastrophic, causing instant contamination of the entire fuel system with metal particulates. Chances are, if you’re looking at this page, you’re well aware of the problem. Below we will discuss the reasons for this failure, how to diagnose a pump failure, and show you the parts you need to properly fix your vehicle.

Why Does it Fail?

The short answer: lack of lubricity. Lubricity is most commonly defined as the ability of a fluid to minimize the degree of friction between surfaces in relative motion under load conditions.

The CP4 injection pump creates higher pressures with less volume than its predecessor, the CP3 pump. Although this makes it a more efficient pump, the lack of volume creates a lack of lubrication since these pumps rely on the diesel fuel to act as a lubricant.  In addition to the higher pressure and lower volume, the removal of sulfur from modern diesel fuel (Diesel #2 or Ultra-Low Sulfur Diesel) also destroys compounds that exist in the fuel naturally that would normally contribute to increased lubricity. Some fuel resellers mix lubricity-increasing additives into their fuel prior to sale, but this is not consistent and not well-regulated. Using a commercially available diesel fuel additive can be helpful, but cannot be guaranteed to prevent CP4 pump failure.

Diagnosing a Pump Failure

The LML and LGH CP4 pumps most commonly fail due to this lack of lubrication which causes internal metal parts (the drive cam, cam follower or pump piston, as well as the housing itself) to rub against each other and begin to shave off small metal particles. These particles are immediately distributed throughout the fuel system causing catastrophic failure. Some pumps actually seize up completely and burst the aluminum housing open as a result of this failure.

Using lubricity additives doesn’t guarantee that your pump won’t fail someday, so it’s important to know what steps to take when it happens to you.

If you’re experiencing a hard start or no start, or are getting the following trouble codes; P0087, P0088, P0191, or P128E, a pump failure could be the problem.

Remove the CP4 pump and then the fuel pressure regulator for inspection. If the body casing of the pump is cracked, as in the picture, or you find metallic debris on the fuel pressure regulator screen (pictured right) this is indicative of a pump failure.

Repairing Your Vehicle

GM Mandates that the below steps be performed:

• Replace: Pump, rails, injectors, all high pressure fuel lines, return lines, and fuel filter
• Clean and flush: All fuel chassis lines, filter pipes, and other engine mounted fuel system pipes (low pressure)
• Remove and clean/flush: Fuel tank and fuel sender has put together complete repair solution for LML/LGH CP4 Pump failure using all OEM parts (pictured below.) Simply flushing the fuel system is inadequate, and could lead to residual contaminants in your fuel system. Contamination is the number one cause of repeat injector failure, and replacing all of the fuel system components is the only way to prevent recurring contamination issues.

We offer this kit in a few different convenient configurations to meet your needs, by default it includes:

  • Bosch OEM New or Remanufactured LML Injectors (8)
  • BOSCH® OEM New CP4 Pump (Updated housing, camshaft, roller tappets and gear pump)
  • Bosch OEM New Fuel Rails (2)
  • Bosch OEM New Return Line Assembly
  • GM OEM New High Pressure Fuel Lines (Pump to rail, rail to rail & rails to injectors)

Click here for more information and to purchase the kit for your 2011-2016 Duramax LML Truck.

Click here for more information and to purchase the kit for your 2011-2016 Duramax LGH Truck or Van.

Give us a call or click today and get back on the road!


703 thoughts on “Duramax LML / LGH CP4 Pump Failure – Technical Bulletin

  1. Could you please email me a copy of this LGHCP4 pump failure tech bulletin. Had to do a $10,000 replacement of fuel system on my 2014 gmc 3500 due to metal shavings. Trying to negotiate warranty with General Motors. Thank you for your assistance.

    1. Good morning – We will send over a copy of the tech bulletin text right away. Thanks for stopping by!

      1. Hey Brother, just bought a 2015 Chevy Silverado 2500. Only has 55000 miles on it. Would you please send me the tech bulletin? Do you think a formal recall will come about?

        Thank you,


        1. Hello Robert,

          We have sent the bulletin your way. Unfortunately, we have not heard of any formal recall coming into effect. Thanks for stopping by!

          1. I have a 2011 GMC Sierra 2500HD diesel LML. Read article in TrailerLife. Had no idea this was a problem. Have 82,00km on truck. Do you think GMC would cover this as a preventative measure, keeping good will of customer? Would you please send me the Technical Bulletin. Thank you very much. Now I am apprehensive about worthiness of my truck.
            Thanks Again.
            Derm Strong, in Canada

          2. I have a 2016 Duramax with 108,000 miles and the fuel pump had completely failed. Can someone send me the bulletin?

          3. Hi Mark,

            Sorry to hear about your truck. We will send a copy of the bulletin your way. If there is anything we can do to assist you with your truck please give us a call at 1-800-500-0980.

          4. Please send me a copy of the SB for the Duramax CP4 failure. I have a 2015 that has not failed but I’m concerned it will fail at anytime. What suggestions do you have to be proactive to prevent the failure?

          5. Hi Gary,

            While we don’t have a service bulletin, I’d be happy to send over a copy of the blog post for you. Replacing the pump with the Cp4.2 or a CP3 conversion, running additive for increased lubricity, and using a FASS lift pump to increase the quality of the fuel being delivered and provide extra filtration are all recommended.

          6. Hello looks like I’m having this problem I’ve been replacing everything and it won’t start. I’m actually on the road. As soon as I get home I’m gonna pull the regulator and pump and check it. If you can send me any kind of info I really appreciate it I know this is an old post thank you so much

          7. Hi Jose – We have emailed you a copy of the article. Please let us know if you have any questions or need help with some replacement parts. Give us a call at 800-500-0980 if you have any questions!

          8. Hello – wondering if this is still active 2+ years later but it looks like I may have the same issue – 2012 2500hd . Any chance you would send a copy of the bulletin my way? Thanks in advance – Raymond

          9. Hi Raymond – I have sent over a copy of the article for you. Please let me know if we can help you with anything else!

          1. Jim, can you please send me a copy of the bulletin as well? My truck just died this morning and I fear I have the same problem.

            Thanks, Leo

          2. Hi Leo- Jim is out of the office today, but I’ve emailed you a copy of the article. Please feel free to give us a call if you have any questions or if we can help you with the parts to get your truck back on the road.

          3. My 2011 GMC 6.6 has similar symptoms. Could you please send me a copy of the bulletin? Thanks

          4. Hi Jeff- No problem, we sent a copy of the article to your email. Please let us know if you have any questions or if we can help you get your truck back on the road.

          5. Jim, I think we may have the same problem as well. could you please send over any information on possible recalls.

          6. Hi Aaron- Unfortunately we don’t have any additional information available regarding recalls, however we have sent a copy of the article to your email for reference. Please let us know if we can be of any further assistance.

          7. needing a copy of the bulletin as well. . i have a 2016 silverado Duramax 2500 , with injector pump out. has been at Sunrise GMX dealership going on 2 months and they wont even return a damn phone call. still under warranty. please send asap. Isnt’ Morgan & Morgan have a class action suit against GM now ?

          8. Hi Ryan- Sure, we sent it over via email. Please let us know if we can help!

        1. Hi Bill- We Don’t have a GM bulletin to distribute, however we are happy to share a copy of our article as we have done for many other customers. We’ll email it to you right away, please let us know if you have any questions or if we can help with parts for your truck.

      2. Please send me the bullitin concerning the fuel pressure pump failure. I bought a new 2015 High Country Duramax and just experienced the fuel pump failure. Dealer is still repairing the problem and I want all the information so I can at least fight a little!!!! Estimate for repair is 10 K.

          1. Hello
            Would you be able to send me a copy of that tech bulletin for the CP4 injection pump. my 2015 3500 just went into the dealership for a repair.
            Thank you

          2. Hi Justin- Just sent it over, please let us know if we can help you with any parts to get your truck fixed.

      3. Just curious if I could get a copy of the technical bulletin about the pump failure for the Chevy truck from 2011 to 2016? I have a friend that owns one of those trucks and I’d like to give it to her! ?

      1. I would be interested to learn about the class action suit. What is it called and contact info.

        Also the Tech bulletin on this as the dealer just quoted me 10k on my LML with 84K on the odo

        1. We’ll send over a copy of the blog post right away for you. I’m afraid we don’t have any details on any pending legal action. Let us know if you have any other questions!

          1. Can you please send me a copy too! Our truck just died on us this morning.
            Thank you

          2. Hi Michelle- I’ve emailed a copy of the article, please let us know if we can help you out with the parts necessary for your repair. Thanks!

        1. Hi John- We emailed a copy of the article over, please let us know if we can be of any further assistance!

    2. Hello, Michael.

      Could you please send me a copy of the bulletin? I have a 2015 Chevrolet 2500HD LTZ. Love this truck! Thank you.

      1. I have a 2016 Chev Duramax. Just cracked 75k. I would love to have a copy of the SB to reference when I request a pre-emptive replacement.