P0455 Engine Code Explained: Causes, Symptoms & How To Fix It

What Does Code P0455 Mean?

• P0455 definition: System Gross Leak Evaporative System Malfunction
• Issue Severity: LOW– Continued driving for a short period of time is okay.
• Repair Urgency: Get this code fixed withing the next month to prevent issues related to the emissions system including failed inspections.
• Diagnosis: It is important to complete the entire diagnostic process when diagnosing the P0455 code. This DTC can be triggered by just about anything in your vehicle’s EVAP system from a loose gas cap to a defective part. Use the FIXD Sensor and app to diagnose P0455 yourself, see the most likely fix and cost, access our Mechanic Hotline, and more.
• Common Reason: Code P0455 is often related to a loose gas cap.

The evaporative emission control (EVAP) system prevents fuel vapors from escaping into the atmosphere. You can learn everything there is to know about evaporative emission control (EVAP) systems by reading this article. The fuel vapors from the fuel tank are absorbed and stored by charcoal pellets in the charcoal canister. The vent control valve is controlled by the engine control module (ECM) and allows air to flow into the charcoal canister to purge the gas vapors into the engine air intake to be burned. The flow of the gas vapors from the charcoal canister to the engine air intake is controlled by a purge valve. The vent control valve is normally opened when the engine is on, and the purge volume control valve is normally closed and is controlled by the ECM to open when it is ready to purge the stored fuel vapors from the charcoal canister.

However, the ECM occasionally performs leak tests to ensure the evaporative emission control system is working properly when the vehicle is turned off. During the leak test, the ECM closes the vent control valve to create a sealed EVAP system. If the EVAP system does not maintain the pressure, the ECM recognizes an evaporative emission control leak. In the case of P0455, it is a very large leak. This is usually indicative of a loose, broken, or missing gas cap.

P0455 Causes

• Missing, defective, damaged, or loose gas cap (*most Common)
• Faulty or stuck EVAP vent control valve
• Faulty or stuck EVAP purge volume control valve
• Cracked or disconnected EVAP hose
• Cracked or damaged charcoal canister

P0455 Symptoms

• Check Engine Light is on
• A slight decrease in fuel economy
• Gasoline smell
• Commonly associated with error codes: P0440, P0441, P0456, or any other EVAP-related codes

How Do I Fix Code P0455?

With a P0455 code, the first step is to get it properly diagnosed to figure out what is causing the malfunction in the EVAP system. Using the live data function of the FIXD sensor and app allows you to read and analyze fuel trims to properly diagnose a P0455 code.

> Click here to get FIXD for $19.99 for a limited time!

If you have checked your gas cap and other common issues associated with this trouble code and haven’t been able to diagnose this issue at home, we recommend finding a RepairPal-certified shop to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

How Much Does It Cost to Fix Code P0455?

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0455 code.

Possible Repair Costs for P0455

When it comes to making repairs associated with the P0455 code, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

• Gas Cap $20-$60
• EVAP Line $20-$100
• EVAP Vent Control Valve $150-$200
• Purge Volume Control Valve $150-$200

DIY Steps to Diagnose Code P0455

If you’d like to try to fix code P0455 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Diagnosis can require some specialized equipment beyond what the FIXD Sensor can provide, but this is usually still a beginner-level diagnosis. 

DIY difficulty level: Easy

This repair is easy enough for beginner-level DIYers to attempt.

Tools/parts needed (our top picks from Amazon):

• FIXD
• Pliers or screwdriver to secure a loose hose(s)
• EVAP smoke machine leak checker
• Vehicle specific service manual

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

Use FIXD to scan your vehicle to verify P0455 is the only code present. If other codes are present, they must be addressed first. If it is paired with P0441, P0440 and/or P0456, there is most likely a solenoid failure or a more complex EVAP leak. We recommend that you read our article on how to quickly diagnose your check engine light.

STEP 2: INSPECT GAS CAP. 

Inspect your gas cap to see if it is loose or damaged. If your gas cap is loose, tighten it and clear the code. Inspect your gas cap for physical damage or deterioration. However, it should be noted that damage to the gas cap or deterioration of its components is not always noticeable. If your gas cap was not loose and you do not see any indications of failure, try replacing the gas cap anyway and clearing the codes. Gas caps are relatively inexpensive and are often the fix for code P0455.

STEP 3: PERFORM EVAP SYSTEM LEAK CHECK.

If the fuel cap didn’t fix it, perform an EVAP system leak check. To do this, pinch off the vent tube to the EVAP Vent Control Valve. Pressurize the EVAP system with an EVAP smoke machine leak checker. Check to see if you see any smoke leaking out from any hoses or seals. If there are any leaks, repair leaks and check to see if the concern is resolved.

STEP 4: CONSULT A PROFESSIONAL.

If at this point the vehicle is still setting the same code, you may have an electrical problem and will need to bring it to a shop to have further diagnostic work performed.  

Common P0455 diagnosis mistakes

It is important to complete the entire diagnostic process when diagnosing P0455. Don’t overlook a loose or faulty gas cap as this is the most common culprit that cause the check engine light to come on for this code.

Still Need Help Fixing Code P0455?

If you’ve followed the steps above and are still experiencing a lean engine condition and code P0455, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price. Don’t have a FIXD Sensor yet? Click here to get yours for just $19.99, including a free 14-day trial of FIXD Premium!

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Fixed It But The Check Engine Light Is Still On?

Check engine light sometimes need to be reset manually, check out our article:

How to Reset Your Check Engine Light | 4 Ways To Clear It (With or Without a Scanner)