Trouble Code P0451: EVAP Emission System Pressure Sensor Performance

If you’re having issues with your evaporative emissions system, or EVAP system, your vehicle may show trouble code P0451. Whether or not you have driving performance issues, you’ll want to know how do I fix trouble code P0451? Discover how to troubleshoot and repair common issues related to this error code and restore your vehicle.

What Is Trouble Code P0451

A trouble code P0451 means your EVAP system has a pressure leak. This could be caused by a number of damaged or loose components, depending on the symptoms. Your EVAP system is essential for reducing your vehicle’s emissions. As your vehicle sits, vapors are released from the fuel. A leak in the system allows these vapors to escape into the environment.

A properly sealed EVAP system creates enough pressure to send fuel vapors from your fuel tank through a series of rubber hoses and metal tubes to your fuel canister. This canister has a charcoal filter and safely stores vapors until your engine is started.

Once your engine starts, the purge valve opens, vapors are sent to the engine and burned as fuel. This complete system allows you to greatly reduce the overall emissions of your vehicle, while safely sealing fuel vapors out of your environment.

Your powertrain control module controls the purge valve. Because of this, and the wide range of components that make up your EVAP system, there could be a range of symptoms, causes and solutions for trouble code P0451.

Typical Symptoms

So, what does the code P0451 mean? The most common symptom of this trouble code is simply your malfunction indicator lamp being illuminated. However, that doesn’t mean it isn’t an issue that should be fixed. You could also experience reduced fuel efficiency, and a vehicle stored in a confined space, such as a garage, may reduce the air quality.


Any leak throughout the entire EVAP system could signal trouble code P0451. Here are just a few common causes that can create this error code:

  • Loose fuel cap
  • Clogged or damaged fuel tank pressure relief valve
  • Cracked, rotten or burned EVAP hoses
  • Cracked or damaged filter canister
  • Damaged EVAP pressure sensor

Each of these areas will need to be inspected and repaired in order to restore your EVAP system. Because of the variety of parts involved, you may also see related codes, such as P0450, P0452, P0453 and more. These may be caused by the same or similar damage.

Solutions and Repairs

It’s best to check the most likely and easy-to-fix issues before looking at the more intricate solutions. By far the easiest fix is a loose gas cap. Ensure your gas cap creates a firm seal, otherwise you’ll need to replace it.

Following that, another common issue is cracked, burned or rotten hoses. EVAP hoses can be exposed to extreme heat and cold, so small areas of the hose could be damaged. Check the entire length and, if possible, use a smoke machine to quickly find the leak. You’ll need to replace the damaged section of hose in order to reseal your EVAP system.

A voltmeter can help you determine whether your EVAP pressure sensor is working correctly. You may have an issue with the electrical connections or the sensor itself. Check your service manual for the proper way to inspect this sensor, as it’s usually located at the top of your fuel tank.

Finally, there may be an issue with your powertrain control module. While not as likely as other issues, this issue shouldn’t be ruled out. Once you’ve inspected every system related to your OBD-II scanner error code P0451 problem, clear the code and see if you’ve solved all the issues with your EVAP system.

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