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P0191 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P0191 is an OBD-II Code that refers to Fuel Rail Pressure Sensor Circuit Range/Performance

Meaning

A P0191 code is caused by an ECM (Engine Control Module) receiving a signal that power control module (PCM) regulates the amount of fuel that is released into the combustion chambers by controlling the fuel injectors. This approach lowers tailpipe emissions. The power control module must always be aware of the fuel pressure in order to function correctly.

Causes

Common causes for this code include:

  • Faulty fuel pressure sensor, regulator, connector or sensor circuit

Symptoms

The symptoms of a P0191 code are:

  • Check Engine Light on.
  • The fuel efficiency will decrease.
  • Slowing down and stalling or hesitation in the engine.
  • When the car comes to a halt, the engine may turn off.
  • The exhaust pipe has an odd odor.

Diagnosis

To diagnose a P0191 DTC code, a technician would:

  1. Use a scan tool to check for the existence of a P0191 code and perform a test drive.
  2. Disconnect and check all connectors between the power control module and the fuel pressure sensor including the wiring of the fuel rail pressure sensor.
  3. Use a test fuel pressure and check for corrosion between the battery voltage and ground on the power control module.
  4. For this code, also replace any faulty components that may have been found during diagnosis such as a fuel rail pressure sensor before troubleshooting further.

Common mistakes

The following are common mistakes when diagnosing the trouble code P0191:

Not performing a visual test or replacing parts unnecessarily 

A weak or frayed electrical connection, a faulty fuel pressure regulator, or a damaged fuel pump are all things that go undetected during a diagnosis and repair.

Setting or clearing the code without first verifying the problem (This will cause further issues if it turns out that there is not an actual fault)

Not checking for leaks in the fuel rail system before continuing with diagnostics.

How serious is this?

A P0191 code is known to cause drivability issues. The vehicle may stall out or hesitate when it is driven while this code is present. There may also be a rise in gasoline usage, which can be expensive. It is critical to take the code seriously and have it diagnosed and fixed as soon as possible.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Replacing the fuel pressure sensor
  • Replacing a wiring harness or connector
  • Replacing the fuel pump
  • Inspect the fuel injector for contamination or blockage.
  • Inspect any electrical components that may have been damaged by water, such as the power control module, relays and connectors. 
  • Inspect all vacuum hoses for any damage, tears or holes in the hose material.

Related codes

A P0191 is related to and may be accompanied by the following codes:

P0171, P0172, P0174, P0175, P0176, P0177, P0178, or P0179 - This means that the fuel delivery system up to the cylinder is operating at optimum levels.

P0100 – In this case, there is a problem with the idle speed control circuit which regulates airflow from idle and low speeds.

P0420 – This code indicates catalytic converter efficiency below threshold level. It may also be accompanied by a lean condition in bank 1.

C1226 – The manifold absolute pressure signal is incorrect for a given load and speed because a vacuum hose has been removed or broken off between the engine intake manifold and throttle body.

How much does it cost to fix the P0191 code?

The repair cost of a P0191 code ranges from $100 to $300. The cost is largely dependent on the type of fuel infrastructure that needs to be replaced. It is best to have the code diagnosed early on in order to prevent further damage or issues with drivability or any further costly repairs.

Conclusion

In conclusion, the P0191 code can cause drivability issues, which are detrimental to the longevity of the car. It is best to diagnose and repair this code as soon as possible in order to prevent further damage or costly repairs.

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