Replacing The Evap Fuel Tank Pressure Sensor: Step-By-Step Guide

The fuel tank pressure sensor is an integral part of a car's evaporative emissions system, also known as EVAP. It is placed atop or inside the fuel tank and is responsible for monitoring pressure to detect leaks and faulty gas caps. When the sensor detects a problem, it signals the engine computer by illuminating the check engine light. While it is possible to replace the sensor yourself, it is recommended to consult a professional to avoid any damage or malfunctions. The cost of replacing the sensor ranges from $280 to $600, including parts and labour.

Where is the fuel tank pressure sensor located?

The fuel tank pressure sensor is usually located on top of the fuel pump module, mounted on top or inside the fuel tank.

To access it, you will need to drop the tank. The sensor is available with the evap hose that routes the fuel vapors from the tank to the rest of the system.

The fuel tank pressure sensor is an integral part of your car's evaporative emissions system, also known as the EVAP system. The EVAP system is designed to keep all gasoline vapors within your car's fuel system after fuelling up at the gas station.

The FTP sensor monitors pressure to detect evaporative leaks and loose or faulty gas caps that may be preventing fuel vapors from being contained in the EVAP system.

What does the fuel tank pressure sensor do?

The fuel tank pressure (FTP) sensor is an integral part of a vehicle's evaporative emissions system, also known as the EVAP system. This system is designed to capture and recycle fuel vapors from the fuel tank, preventing their escape into the atmosphere.

The FTP sensor monitors the pressure, both positive and negative, inside the fuel tank. It detects evaporative leaks and loose or faulty gas caps that may prevent fuel vapors from being contained in the EVAP system. By monitoring the rate of vacuum increase, the sensor determines the purge volume flow rate, which is used to detect leaks. If the leak rate exceeds the stored value, a diagnostic trouble code (DTC) is set by the powertrain control module.

The FTP sensor also helps identify leaks in the fuel system, alerts drivers to defective gas caps, and signals the engine computer about the EVAP system's proper functioning. It is crucial for regulating fuel consumption and maintaining compliance with emissions regulations.

A malfunctioning FTP sensor can cause issues such as an illuminated check engine light, decreased fuel efficiency, rough idling, and difficulty starting the engine or stalling.

Symptoms of a faulty sensor

The fuel tank pressure sensor is an integral part of your car's evaporative emissions system, or EVAP system, which is designed to capture and recycle fuel vapors from the fuel tank and prevent them from escaping into the atmosphere. The sensor monitors the pressure, both positive and negative, inside the fuel tank. This helps to identify leaks in the fuel system, alert you to a defective gas cap, and regulate fuel consumption.

Illuminated Check Engine Light

The check engine light is perhaps the most common and obvious indicator of a problem with the EVAP fuel tank pressure sensor. This light can be triggered by various issues, so it's essential to have a qualified mechanic diagnose the vehicle to identify the exact cause.

Engine Stalling and Loss of Power

A faulty sensor can cause the engine to stall or experience a loss of power due to incorrect readings sent to the Powertrain Control Module (PCM). This can lead to a lean air-fuel mixture, making it difficult to start the engine or causing it to stall.

Increased Fuel Consumption

A bad sensor may not accurately calculate fuel usage, resulting in increased fuel consumption. This symptom may be subtle at first but can become more noticeable over time.

Rough Engine Idle

A malfunctioning sensor can cause the engine to run improperly, leading to rough idling. This is often accompanied by a noticeable vibration or shaking sensation in the cabin of the vehicle.

Difficulty Starting the Engine

In addition to stalling, a faulty sensor can also cause difficulty starting the engine. This is because the Powertrain Control Module may not receive accurate information about the pressure inside the fuel tank, leading to an incorrect air-fuel mixture.

If you notice any of these symptoms, it's important to consult a qualified mechanic to diagnose and address the issue promptly.

How to check the sensor

The fuel tank pressure (FTP) sensor is an important part of the evaporative emissions control system. This system is designed to capture unburnt fuel vapors and reintroduce them back into the fuel system. The FTP sensor is responsible for detecting leaks in the fuel system, whether it be an evaporative leak or a bad seal on the fuel cap.

Check the Engine Light

When the FTP sensor malfunctions, one or more diagnostic fault codes are typically stored, and the vehicle's check engine light will illuminate. Diagnostic trouble codes (DTCs) such as P0442, P0452, P0453, and P0455 could indicate a faulty FTP sensor.

Loss of Fuel Economy

A sudden decrease in fuel economy, such as a 2-3 mile loss per gallon, could be a sign of a faulty FTP sensor. This is due to incorrect signals being sent to the engine control module, resulting in poor fuel usage and a decrease in miles per gallon.

Noticeable Fuel Odor

A rich fuel odor emitted from the vehicle is a common sign of evaporative emissions system-related issues, including a potential failure of the FTP sensor.

Stalling or Hesitancy Under Acceleration

Intermittent stalling or hesitation when accelerating could be caused by a faulty FTP sensor. This is because the sensor manages the air-to-fuel ratio, and a faulty sensor may send incorrect signals, leading to a compromised combustion process.

Hard to Start Vehicle

If the vehicle is continuously difficult to start, the FTP sensor may be the culprit. A faulty sensor can lead to a lean air-fuel mixture, with a higher volume of air and a smaller volume of fuel, making it challenging for the engine to start.

To confirm that the FTP sensor is the issue, you can perform a few additional checks. First, consult an automotive professional, as there could be other reasons for the issues you're experiencing. Second, check the three wires connected to the FTP sensor: the ground wire, the voltage wire that goes to the engine control module, and the wire that returns volts to the ECM. Finally, you may need to drop the gas tank to access the FTP sensor, which is typically mounted on top or inside the gas tank.

What happens when the sensor goes bad?

When the EVAP fuel tank pressure sensor goes bad, there are several things that can happen, and it's important to be aware of these symptoms to take appropriate action. Here are some detailed explanations of what can happen when the sensor malfunctions:

Check Engine Light Illuminates

The most common symptom of a faulty EVAP fuel tank pressure sensor is the illumination of the check engine light on your dashboard. This warning light is triggered when the sensor detects a problem or leaks in the fuel system, and the engine control module receives this information. It's important to get your vehicle diagnosed to identify the exact issue and prevent further damage.

Poor Fuel Economy

A bad fuel tank pressure sensor can lead to a sudden decrease in fuel economy. You may experience a noticeable drop in the number of miles per gallon, resulting in higher fuel consumption and costs. This is caused by false information sent to the car computer about fuel usage, leading to an inappropriate fuel mixture.

Engine Stalling and Hesitation

A faulty sensor can cause issues with the combustion cycle, leading to engine stalling and hesitation. The sensor plays a crucial role in calculating the fuel-air mixture ratio for combustion. When it sends false readings, the combustion process is compromised, resulting in improper fuel burning and engine performance issues.

Hard Engine Starting

A bad sensor can make it difficult to start the engine. False readings from the sensor can lead to a lean air-fuel mixture, where there is a higher volume of air and a smaller volume of fuel. This inappropriate fuel mixture can make it challenging for the engine to start and may require multiple attempts.

Failure of Emission Tests

When the EVAP fuel tank pressure sensor malfunctions, your vehicle is likely to fail emission tests. This is because the sensor plays a crucial role in trapping unburnt fuel vapors and transporting them back to the fuel system, reducing environmental pollution. A faulty sensor can cause an increase in emissions, leading to test failure.

Noticeable Fuel Odor

A rich fuel odor emitted from your vehicle is another symptom of a faulty fuel tank pressure sensor. This is a common issue when the evaporative emissions system is not functioning correctly, and you may notice a strong fuel smell while driving or even when the car is stationary.

Lack of Power

In some cases, a bad fuel tank pressure sensor can result in a lack of engine power, especially during heavy acceleration. You may experience a sluggish response from your vehicle, with subdued performance that affects your driving experience.

It's important to note that while some of these symptoms may be indicative of other problems, a faulty EVAP fuel tank pressure sensor can cause significant issues. Therefore, if you notice any of these signs, it's recommended to consult a professional mechanic for proper diagnosis and repair.

Frequently asked questions