5 Reasons Behind P128E Duramax Error Code And Their Solutions

What does p128e Duramax mean? It means that the fuel rail pressure is too high or too low than the expected pressure rate.

This error code can show for many reasons. These reasons include leakage in the sump, a faulty fuel filter, the wiring harness is chaffing on the air conditioning lines, and more.

This article will elaborately discuss all these reasons and their solutions. Let’s dive in.

P128e Duramax

Leakage in the sump  The truck may completely lose power
Faulty fuel filterCheck Engine light message
The wiring harness is chaffing on the air conditioning linesFuel filter change message
Fuel contaminationThe vehicle will not start
Dirty fuel lines and fuel tank
The vehicle is very slow
The truck goes into low power

Let’s discuss the causes for the p128e duramax code and their solutions in detail.

Leakage In The Sump

Your 2014 LML truck can show a P128E error code when the fuel is 25% or less. The truck can lose power when you stop it and will not start again. In this case, you need to pull the fuse of the FASS pump, run the engine, and check if you lose prime or your vehicle runs roughly.

If you lose prime or your vehicle runs rough, then it indicates a leakage in the sump. If your truck’s engine runs ok, then the connector of the sensor on the fuel rail can be dirty and can cause this problem.

Solution: To solve this problem, you need to replace the sump. You also need to clean the connector of the sensor on the fuel rail.

Faulty Fuel Filter

Sometimes during driving, your truck can lose entire power and shut down. You will get a fuel filter change message and check engine light message in this situation. The only error code you will see in this case will be P128E. The reason behind this issue is a faulty fuel filter.

Solution: In this case, you are required to replace the faulty fuel filter to solve this issue.

The Wiring Harness Is Chafing On The Air Conditioning Lines

At times you can get the P128E error code on your 2012 GMC Savana car. In this case, you will face the not starting issue, and your car will not start. This problem can happen if the wiring harness is chaffing on the air conditioning lines.

Also Read: P0087 Duramax Fixing with Reasons Explained

Solution: To solve this 2012 Duramax code p128e issue, you have to follow the manufacturer’s suggested diagnostic and repair processes. These processes comprise mending any wires with chaffing damage and tie strapping them safely far away from the air conditioning lines.

Fuel Contamination

Your 2014 6.6l Duramax truck can sometimes show the P128E error code. You will also see your vehicle goes into low power and doesn’t want to start when it is hot. In addition, you will find an extremely small piece of debris on your truck’s fuel pressure regulator, causing the Fuel rail pressure performance P128E error code.

This problem is generally caused by fuel contamination of water, gasoline, or diesel exhaust fluid in the diesel. It can also be caused by fuel contamination in both the fuel pressure regulator and fuel pressure regulator valve.

Solution: To solve it, firstly, you have to drain the fuel tank. Then, you need to replace the fuel filter and replace both the regulator and the pressure regulator valve.

Dirty Fuel Lines And Fuel Tank

Sometimes your 2011 LML truck can show the P128E error code and won’t start. Even if the truck starts sometimes, it is very slow. You may have replaced the CP4 pump, both fuel rails, and injectors. You may also have changed the fuel filters two times, and still, this problem won’t be solved. This issue occurs because of dirty fuel lines and the dirty fuel tank.

Solution: In this case, clean all the fuel lines on the engine and clean the fuel tank to solve the issue. If still the problem has not been solved, replace all the fuel lines on the engine and replace the fuel tank.

A Helpful Tutorial You May Need!

Frequently Asked Questions (FAQs)

What is p128e code?

The P128E code meaning is that the fuel rail pressure is lower or higher than anticipated. In specific engine operating situations, the ECM examines the real fuel rail pressure conveyed from the fuel rail pressure sensor and compares the value to an established programmed value. If the values are beyond the standardized range for an established period, the P128E will be set.

Where is fuel rail pressure sensor?

You can find the fuel rail pressure sensor near the fuel rail that is connected to the ECU (Engine Control Unit).


Whether you found the 2016 duramax code p128e on your 2016 6.6l Duramax truck or found the p128e code in any other model truck, it is important to solve this issue. Fixing the p128e duramax error code can be tough, particularly if you don’t know the reasons behind this error code.

To help you, we come up with 5 reasons and their fixes for this error code. We are hopeful that you can now easily fix the P128E error code issue.

You Can Also Read:

D Conroy

Meet our senior writer and content manager of Automasterx. He has worked in several mechanical garages and mastered different vehicle diagnoses and parts repair. He never stops until finding out the ultimate solutions for any vehicle fault code. However, ensuring the only solid solutions for each vehicle malfunction is his core part of the duty, alongside analyzing fault codes and signals.

Similar Posts