P0456 Engine Code | Evaporative Emission Control System—Small Leak Detected (2024)

Modern cars with internal combustion engines are all about limiting emissions—a feature managed by sophisticated engineering and federal regulations. Part of this technology involves restricting the amount of fuel vapors that escape into the atmosphere, which falls under the evaporative emission control or “EVAP” system. A diagnostic trouble code (DTC) of P0456:

Evaporative Emission Control System Leak (small) indicates a problem with the EVAP system.

Before getting into the specifics of a P0456 code, let’s explore the essentials of the EVAP system and how it works.

• Fuel Tank: As fuel sits in the tank, it evaporates, creating fuel vapors.
• Charcoal Canister: The EVAP system captures these vapors and stores them in a charcoal canister, which is filled with activated carbon. The carbon absorbs and holds the fuel vapors.
• Purge Control Valve: When the engine is running and certain conditions are met, the engine control module (ECM) opens the purge valve. This allows the engine to draw fresh air through the charcoal canister, pulling the fuel vapors into the engine to be burned during combustion.
• Vent Control Valve: The EVAP system also has a vent valve that allows fresh air to enter the charcoal canister when the purge valve is open to draw the fuel vapors out.
• Leak Detection: The EVAP system is designed to be a closed arrangement. If there is a leak, the ECM will detect it and trigger a check engine light, including DTC P0456.

If there’s any good news from this situation, it’s that P0456 is a low-priority problem. This doesn’t mean you should ignore the issue. Rather, you can keep driving but should attend to the code in days or weeks, not months. Besides a check engine light, you may notice a modest drop in fuel efficiency or a slight fuel aroma. Otherwise, a P0456 code has little impact on a car’s operations. In addition, this DTC can cause your vehicle to fail an emissions test.

Let’s dive into what code P0456 causes, typical repairs, and the most common vehicles for this problem.

Possible Causes of P0456 & Their Repair Costs

The essence of DTC P0456 is a small leak in the EVAP system, and that’s the challenge. Many small EVAP leaks are difficult to detect, even for professional mechanics with sophisticated tools. In this case, small means an opening less than 0.02 inches in diameter. To put that measurement in perspective, a human hair has a diameter of 0.001 inches. So, it doesn’t take much of a leak for problems to arise.

Check out the FIXD article on the most common causes of check engine lights.

Let’s break down P0456 repairs into likely trouble spots.

Keep in mind that these are average prices. Some cars may require more expensive parts and additional labor.

Here are more details about the specific parts that can trigger a P0456 code.

Makes Commonly Affected By P0456

While no automaker engineers a car to have known faults, some automobiles fall into predictable trouble areas. In the case of code P0456, FIXD sensor data shows that Toyota vehicles are the most vulnerable, proving that no car is perfect.

Drilling into the details uncovers that the Camry and Corolla, two of Toyota’s best sellers, are at the top of this list. There’s some logic to this, as more cars on the road lead to a greater likelihood of more problems arising. Interestingly, the 4Runner takes the third spot. It’s a popular vehicle but takes a backseat in sales compared to the RAV4 and Highlander, which register at much lower P0456 occurrence rates.

Ford’s worst offender for P0456 codes is the Escape compact crossover, followed by its larger stablemate, the Edge. The Fusion sedan takes third place. Equally interesting is that Ford’s and America’s best-selling vehicle, the F-150, doesn’t show any history with P0456 codes.

Ram doesn’t sell many vehicles beyond its core 1500 pickup. Nonetheless, this truck gets dubious recognition for the frequency of P0456 codes that trigger check engine lights in this model. Ram’s corporate cousin, Jeep, also gets called out for having several models—Grand Cherokee, Wrangler, and Liberty—with dubious P0456 histories.

Nissan completes the P0456 top five brands, making the ‘Hall of Shame.’ The Sentra and Rogue have near-identical occurrence rates among all the vehicles analyzed by the FIXD sensor. Rounding out the company’s unfortunate achievement is the Murano crossover.

“We only show the top models for the top 5 makes in this article. To see the rest, click on our article about how common P0456 is for all of the top 100 vehicles in the US.”

How to Diagnose The Cause of Your P0456 Code

Because there are thousands of diagnostic trouble codes, you’ll want to use an OBD-II scanner to confirm the source of the problem. Devices like a FIXD plug-in sensor with a smartphone app or a convention unit with a wired connection can almost instantly tell you if code P0456 is the reason for the check engine light.

Depending on how much DIY investigating you want to do, gloves, a flashlight, and a rag could come in handy.

Safety Essentials

Before exploring the source of a P0456 code, you’ll want to observe the following:

• Park on a level surface in a safe area
• Because you may encounter flammable fuel vapors, the car should be outdoors and in a well-ventilated setting.
• Ensure there’s no smoking or other ignition sources nearby
• Perform any visual inspection with the car’s engine turned off

Symptoms of P0456 Causes

EVAP leak detection can be a simple task if it involves a faulty gas cap or fuel filler neck. However, things get more complex beyond these efforts. You’ll notice that some P0456 causes can be investigated by a DIYer, while others may require professional intervention, depending on your experience level.

Check to see if any P0456-related technical service bulletins (TSBs) have been issued for your car. This information can often help pinpoint trouble spots with the EVAP system.

Can I drive with Code P0456?

Quick answer: Yes you can continue to drive with the P0456 code

While no check engine light is a “nothing to worry about” event, at least P0456 codes are less worrisome. You can continue to drive with the code and not stress about causing permanent damage to your car. However, this doesn’t mean you have a free pass to ignore the situation. You’ll want to address the problem to ensure maximum fuel economy while minimizing harmful emissions output. Eventually, you’ll need to resolve the trouble if you live in a state with emissions testing. A code P0456 is a sure-fire emissions test failure.

With this in mind, let’s examine what you need to know about driving with a P0456 code.

DIY | How To Fix P0456 Causes

The truth is that there are only a few things a beginner DIYer can do to resolve code P0456. We’ll get into those in a moment. Beyond addressing these issues, resolving a small EVAP system leak requires professional diligence and specialized equipment (e.g., a smoke machine)—elements beyond most novices’ scope. If you have a smoke machine sitting in your garage or workshop, chances are you don’t need to read this article.

Regardless of your skill level, DIY success comes from knowing when to seek professional support as much as it does from completing the task. If your attempts expand the damage, diving too deep into the repair-it-yourself pool can be more expensive than the original repair.

Here’s what a newbie DIYer can handle.

References:

1. Repair-cost estimates, repairpal.com (various dates). Retrieved June 3, 2024, from repairpal.com.