How to Fix the P0191 DTC Code on Duramax (Expert Insights)

The error codes illustrate a path to understanding the specific problems shown by your vehicle. Using these Diagnostic Trouble Codes(DTC), you can select the best possible fix to get your vehicle up and running again.

If your Duramax shows a P0191 DTC, it means the error titles as “Fuel Rail Pressure Sensor Circuit range/performance.” In short, it means the fuel pump pressure is not working as expected and showing negative results to the ECU.

This may keep you wondering what should be done if you get this trouble code in your Duramax. Keep on going through this article to learn more about the symptoms, causes, and best-suited solutions for the DTC P0191.

How to Fix the P0191 DTC Code

What Does P0191 Code Mean On Duramax?

The P0191 DTC shows an issue in the fuel rail pressure difference more than the optimum range. If the fuel pressure within the chamber experiences pressures more than 70psi or less than 20psi, then the vehicle can show you this error code.

If you break down the acronym P0191, the detailed status becomes as follows.

  • P = Powertrain,
  • 0 = Generic (SAE)
  • 1 = Fuel and Air metering
  • 91 = Specific Fault Index (In this case, issue in the fuel pump pressure calculation)

Generally, if you turn on the key, the pump runs for a few seconds to deliver the fuel to the combustion chamber through injectors.

But if the fuel pressure checker becomes faulty, the ECU cannot determine the FRP resulting in the pump running constantly.

How Serious Is P0191 Code On Duramax?

The P0191 code specifically says the issue is with the propelling system of the engine of your Duramax. This means the problem is very serious and requires fixation as soon as possible.

Since the ECU of your Duramax cannot track the inlet and outlet fuel pressure from the pump, it also cannot control the flow. Thus the fuel pump requires quick diagnostic causing the code and repairing.

Otherwise, if you leave this issue untreated, there will likely be more severe damage to your vehicle’s engine. The Duramax can even get stalled while running on a busy road.

What Causes P0191 Code On Duramax?

The P0191 DTC code can occur due to fault or damage caused in the modules or the electrical components.

Its primary cause is the pressure sensor damage, which shows false results to the ECM. But there are some other factors also which can cause a fault in the fuel injection system from the tank to the engine.

  • Fuel Rail Pressure(FRP) sensor damage
  • Fuel Pump damage
  • Drivers Module issues
  • Electronic Control Module(ECM) damage
  • Very Low Fuel and Empty Gas leak
  • Leakage in the fuel injector
  • Faulty Electric Connection in the FRP circuit
  • Opened or Shortened Fuel Rail Pressure Harness

How To Fix P0191 Code On Duramax?

To fix the P0191 check engine code, you must thoroughly check the entire fuel injection sequence. This diagnostic is to be done by the On-Board Diagnostic software, otherwise known as OBD-II.

Step 1: Complete Data scanning By OBD-II

The initial step is to check for the fault in the vehicle’s fuel injection system. There can be single or multiple issues causing the P0191.

Both Automated and manual mechanical scanning is to be done afterward to confirm the issues. This OBD-Ii scanning will give you a Freeze Frame Data using which the next fixation steps are to be completed.

Step 2: Inspecting The Fuel Pump Sensor Data

The FRP Sensor issue is the most common cause of the DTC P0191. Firstly You should check the fuel pump pressure data from the computer.

After that, run the test using a manual pressure gauge to confirm the sensor provides the correct data to the ECM. If the collected data are mismatched, the Fuel Rail Pumpsensor requires repair or replacement.

Step 3: Inspecting And Replacing Electrical Connection of FRPS

The connecting wires of the ECM with the Fuel Rail Pump Sensors require inspection. You can see the changes in the positive and negative terminal voltage readings.

Due to heat and vibration, the wirings can get fried, shorted, or broken. Replacing the connections is the solution to overcome this issue.

Step 4: Repairing Fuel Pump

Sometimes the fuel pump gets clogged due to contamination or low-grade fuel. It can also happen because of dirt and debris inside the fuel line.

All of these results in the over-fueling or under-fueling of the engine through the injector, and hence P0191 code is shown. To overcome this problem, you must clean, repair or replace the fuel pump.

Step 5: Repairing Fuel Pressure Regulator

When the fuel regulator becomes faulty, it regulates an inappropriate amount of fuel from the tank to the injectors. As a result, the fuel pressure becomes more or less than the optimum limit.

You need to inspect and repair the fuel regulator tool to solve this problem. In the worst-case scenarios, the Fuel regulator may require a replacement.

Other Symptoms Of Getting P0191 Code On Duramax

The P0191 trouble code initiates the check Engine Light located on your instrumental panel. When the Furl rail Pressure causes trouble, the regulator fails to regulate the fuel injection.

And you can hear the sound of constant fuel injection when you turn over the vehicle. Moreover, some other symptoms can warn you about the P0191 code.

  • The engine won’t get ignition.
  • Lower fuel economy.
  • Lower acceleration.
  • Sudden stalling while driving
  • High fuel consumption

How Much Does it Cost to Fix Duramax P0191 Code?

Most of the relative sub-issues under the DTC P0191 require either repairing or a replacement of the parts. Therefore two types of costs will be seen. These are the service cost and the part cost.

To get a new fuel pump sensor, you need to pay $60-$100. To replace it with the faulty one, you may pay around $140-$4240, depending upon the workshop type and location.

Can You Drive Your Duramax With code P0191?

It is not advisable to drive your Duramax if it is experiencing a DTC P0191. The vehicle can be driven till the fuel injectors work properly. But in extreme conditions, the vehicle may get stalled on the road.

Moreover, some follow-up damages can also occur if you drive Duramax in such conditions. This includes damage to the Fuel regulator, Drive Modulator, etc.

It increases the risk of getting the repairing of P0191 more expensive. Though you are allowed to drive your Duramax to the nearest workshop if the engine fails on the way, towing can be the only option.


To get rid of the P0191 DTC on your Duramax, you can try replacing the fuel pump pressure sensor yourself in the garage. Because it does not require disassembling the Fuel rail or any major components.

Hence some of the labor costs can be saved. But if budget is not a big deal, it is highly recommended to get your Duramax checked by a certified mechanic to solve the issue effectively.

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