What is Fuel Rail Pressure Sensor? Working, Diagnosing, and Replacement

In you can engine, the fuel rail sensor is a critical part. It is found in diesel engines and many gasoline-injected vehicles. It is a key component in the fuel system of the car. The role of the fuel rail pressure sensor is to monitor the fuel system pressure.

It makes the identification of leaks easier, especially those caused by gasoline evaporation. The performance of the vehicle may suffer if the sensor is malfunctioning. The driver can be made aware of a potential problem by a few indications that are produced by a defective or failing fuel rail sensor.

How Does the Fuel Rail Pressure Sensor Work?

The fuel system is made up of a fuel tank, fuel injector, fuel rails, and fuel pump. The appropriate fuel delivery to the engine is the fuel injection system purpose. In an IC engine, the fuel rail’s primary job is to provide fuel to the fuel injector at all times.

It attaches to the gasoline rail’s center and is linked to the vehicle’s main computer, Engine Control Unit. The sensor gives a signal to the engine control unit (ECU) as it gauges the pressure in the fuel rails.

The ECU evaluates data as it comes in and modifies the timing and volume of fuel injection. Thus, the sensor aids in enhancing the engine’s efficiency under variable operating conditions.

P0191 Error Code – What Does it Mean?

fuel pressure sensor symptoms

P0191 diagnostic trouble code (DTC) is for “Fuel Rail Pressure Sensor Circuit “A” Range/Performance.” It suggests that the fuel rail pressure readings may be abnormal.

It implies that the fuel rail pressure sensor’s signal does not correspond to the value that the PCM sent due to a mechanical or electrical issue.

This error code can also arise due to the following also:

  • OBD-II Error Code – P0171 due to uncontrolled rich fuel system.
  • OBD-II Error Code – P0172 due to uncontrolled lean fuel system.

Thus, from here, you can understand that the electronic fuel injection pressure sensor maintains the proper ratio of lean and rich fuel mixture. The PCM in modern vehicles relies on the fuel rail pressure sensor to send a continuous flow of precise data. Otherwise, it will store the P0191 error code.

What are the Causes of the P0191 Error Code?

If there is a P0191 error code, your car is at risk. Improper mixing and insufficient fuel will lower the engine output. At the same time, extra fuel will increase the wastage of fuel and increase exhaust pollution levels, which could harm the catalytic converter. So, a fuel pressure sensor is highly responsible for controlling the fuel consumption and emissions in your car.

The causes of the triggering of the P0191 code can be due to various electrical and mechanical issues:

  • A problem with the fuel pressure sensor circuit.
  • Too high or low fuel pressure.
  • Accumulation of dirt on the sensor.
  • Defective fuel pressure regulator.
  • Outdated PCM software.
  • A loss in power supply to the sensor.
  • A faulty fuel pressure sensor connector.

What are the Failing Fuel Pressure Sensor Symptoms?

There are a few signs which could indicate that there may be a problem with your car fuel sensor. Here are the major symptoms:

Check Engine Light ON

Whenever there is a problem with your car engine, then the Check Engine light gets ON. So, if the fuel pressure sensor isn’t working efficiently and there is a contradiction in the measurement, it will automatically send the signal to the engine control unit to illuminate the Check Engine light.

However, there can be many other reasons for the Check Engine light getting ON. So, you should also look for other reasons too.

Poor Fuel Efficiency

Your fuel economy and mileage will significantly decrease if your fuel pressure sensor isn’t acting properly.

Your car engine control unit may send too much or insufficient fuel through the fuel rail and into the combustion chamber. Thus, a damaged fuel rail sensor causes the engine to run poorly or consume more fuel.

Difficulty in Starting

Another key symptom of a failing fuel rail pressure sensor is difficulty in starting your car. When your fuel sensor is malfunctioning, it won’t send the correct proportion of fuel and air to the engine. It would cause you to take multiple crankings before getting going. Moreover, you may also find it shutting off the engine after a start.

Vehicle Does not Accelerate

If you are pressing the gas pedal and the car doesn’t accelerate as it should, then you may have a problem with your fuel sensor.

We know that the sensor provides data to ECU, which helps in maintaining the right mixture of fuel and air. However, when it receives erroneous data, the engine control unit is unable to deliver the signal to the fuel system correctly. Because of this, it won’t be able to meet the engine’s fuel requirements.

Engine Stalling

Another probable symptom of a failing fuel sensor is that your engine stalls suddenly while driving. It may also stall while idling. It will make your driving very difficult and even cause risk to your car.

How to Diagnose Fuel Rail Pressure Sensor?

By using a Multimeter:

  • Firstly, locate the sensor on the fuel injection rail.
  • Before starting, disconnect the sensor.
  • Now, set the multimeter probes on the terminals of the sensor.
  • If there is no continuity, then the sensor is defective.
  • After that, reconnect the sensor’s connector.
  • Start the engine and drive for a while.
  • In case the fuel pressure sensor is defective, your car engine will not respond correctly and may even stall.

By using an OBD-II Scanner:

It is a more advanced method of diagnosing the fuel pressure sensor. An expert mechanic will be required to carry out the process. Here are the probable steps –

  • Firstly, with the help of the OBD-II scanner, mechanics will extract the ECU data.
  • They will try to determine the vehicle’s condition to understand the generation of error code P0191.
  • Probably they will test drive your car.
  • It will help the mechanic to get the live data.
  • They will use the fuel pressure tester to evaluate whether the fuel pressure reading is normal or not.
  • They will also use an oscilloscope to test the wiring and verify that the circuitry is working.
  • So, the fuel rail pressure sensor will be defective if the actual reading is different from the reading sent by the sensor or if there is a fault in the wiring.

The fuel sensor is an essential component. So, if your car’s fuel pressure sensor is faulty, then you should replace it ASAP.

Fuel Rail Pressure Sensor – FAQs

What does a fuel pressure sensor do?

The electronic fuel injection pressure sensor is responsible for measuring the fuel pressure. It transmits the pressure reading to the car’s computer. After that, ECU instructs the fuel pump on how much fuel and air mixture the engine needs to run. Due to the fuel pressure sensor, there will be a decrease in emissions. Power, acceleration, and fuel efficiency can be lost if the fuel pressure sensor malfunctions.

Where is the fuel pressure sensor located in the car?

The fuel rail pressure sensor is found near the center of the fuel rail. It is connected to the central computer of your vehicle. You will have to open the car hood and reach out to the intake manifold to find the fuel rail.

What symptoms indicate a faulty fuel pressure sensor?

The most typical warning indications of a defective fuel pressure sensor are as follows:
➢More Fuel consumption.
➢Engine stalling.
➢Check Engine light ON.
➢Difficulty in acceleration
➢Trouble starting the engine

What should be the ideal fuel pressure?

The fuel pressure in the fuel injection system is measured by the fuel rail pressure sensor. When gasoline is fed into the fuel rail, the fuel pump creates pressure, ultimately causing the pressure in the fuel rail. The fuel rail pressure is expressed in psi. Vehicles should have psi readings in the range of 5 and 10.

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Writer at Cars Part Shop

Hello there, I’m Erin Harrison, a writer and auto enthusiast. When you need guidance on vehicle repairs, I want to be your go-to guy.

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