OBD-II Trouble Code: P0456 Evaporative Emissions System (2024)

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OBD-II Trouble Code: P0456 Evaporative Emissions System (1)
Dale Toalston
ASE Certified Technician

OBD-II Trouble Code Technical Description

Evaporative Emissions System - Small leak detected

What does that mean?

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Although generic, the specific repair steps may vary depending on make/model.

The Powertrain Control Module (PCM) at different times performs various testson the EVAP system. OBD II Enhanced EVAP systems are in place to keep fuel tankvapors from venting into the atmosphere, and instead purges them into the engineto be burned.

Regular pressure tests are conducted by the PCM to monitor thesealed system for leaks. The PCM monitors the EVAP system pressure by watchingthe fuel tank pressure (FTP) sensor. When the sensor indicates a small leakin the EVAP system, this code is set.

Related evaporative emission trouble codes include P0450, P0451, P0452, P0453, P0454, P0455, P0457, P0458, and P0459.

Potential Symptoms

There will likely be no noticeable symptoms other than the Malfunction IndicatorLamp (MIL). This is because the EVAP system is a closed system and only controlsfuel tank vapors, not engine management.


Usually this P0456 code is caused by an incorrect or faulty gas cap. Fillingthe fuel tank with the engine running could conceivable cause this code as wellor if the cap wasn't properly tightened. Any of the following could also bethe cause:

  • A small leak in any of the EVAP hoses or fuel tank hoses
  • A small leak in the purge valve or vent valve
  • The EVAP Canister may be leaking

Possible Solutions

First, using a scan tool activate the vent solenoid, sealing the system. Thenmonitor the fuel tank pressure(FTP) sensor.

If the system is sealing properly, the number will stay consistent.If is isn't, the pressure sensor will show that as well.

If the system slowlyleaks, use a smoke machine and watch for smoke exiting the system at any EVAPcomponent. Any where there is smoke exiting the system, that is the faulty component.Do not pressurize the EVAP system with air pressure. Doing so can damage thepurge and vent solenoids in the system.

Other EVAP DTCs: P0440 - P0441 - P0442 - P0443 - P0444 - P0445 - P0446 - P0447 - P0448 - P0449 - P0452 - P0453 - P0455

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OBD-II Trouble Code: P0456 Evaporative Emissions System (2024)


OBD-II Trouble Code: P0456 Evaporative Emissions System? ›

A failure to maintain the correct fuel tank pressure results in trouble code P0456. This means that a leak is allowing vapors to escape, either directly from the fuel tank or from related hoses and parts.

What is the most common cause of P0456? ›

For example, a very common cause of the P0456 code is a loose gas cap. In some cases simply tightening a gas cap may already resolve the issue, while many instead people rush immediately to replace a specific component in the EVAP system.

How much does it cost to fix code P0456? ›

Many times the repair is a new piece of hose, a rubber gasket between two components, or a new fuel cap, all of which will keep the repair portion of the bill under $50.

Is it okay to drive with a P0456 code? ›

A vehicle will continue to run even with a P0456 code because EVAP system leaks are often barely noticeable. The only symptoms you may observe that could be associated with this trouble code are the following: Illuminated check engine light. Slightly increased vehicle HC emissions from the leak point.

Can I fix an EVAP leak myself? ›

Depending on where the leak is in the system and whether or not there is another damage, you can expect to pay up to $600 or so to fix a leak in your vehicle's EVAP system. If you have an OBD2 code reader at home, you can diagnose the problem yourself, but it's best to leave the fixing to the professionals.

Will an evap code clear itself? ›

Even in cars that automatically clear the P0455 code, don't expect the code to be cleared right away. The EVAP system checks for leaks while you drive your car for some time, so you'll probably need to drive for a while before the check engine light turns off and the code is cleared.

How do I permanently remove P0456? ›

It's just like a regular trouble code, except it can't be cleared with a scanner, or by disconnecting the battery. A permanent code is stored in non-volatile memory and the only way to erase it is for the car to run the same test that caused the code to set in the first place, but, of course, it needs to pass the test.

Where is the evaporative emission system located? ›

EVAP system components

Inside the tank, there is a float that signals the computer systems and/or fuel gauge as to how much fuel is in the tank. On newer vehicles, the fuel pump, fuel, filter, and fuel pressure regulator may also be housed inside the fuel tank.

How much does it cost to fix an evap leak? ›

The national cost for an evaporative leak detection pump replacement with CarAdvise in 2024 is between $69 and $463 with an average of $202.

Can a loose gas cap cause a P0456 code? ›

A gas cap seals your fuel tank and allows it to create a pressurized environment. Even if you don't completely screw on your gas cap it could cause a vapor leak and trigger error code P0456. Inspect and tighten or replace your gas cap and see if it removes your problem code.

What is the code P0456 on a obd2 scanner? ›

What does OBD-II fault code P0456 mean? Code P0456 indicates a small leak detected in the Evaporative Emissions (EVAP) system. The evaporative emissions (EVAP) system is designed to prevent fuel vapors from escaping into the atmosphere. To accomplish this, the vapors are captured and stored.

What happens if I don't fix my evap system? ›

When you don't fix an EVAP problem, the check engine light will stay on, masking other problems that might occur. Of course, if local regulations require passing an emissions test, your vehicle will fail. Finally, harmful emissions are being released into the atmosphere.

Where would an EVAP leak be? ›

This can occur through cracks or loose connections in the hoses, pipes, or the gas cap that are part of the EVAP system. A common indicator of such an EVAP leak is the illumination of the check engine light, often triggered by the failure to pass a pressure test conducted by the system's control module.

How to fix evaporative emission system leak detected very small leak? ›

The simplest solution is to remove and reattach the gas cap. Once you do, clear the code on the OBD-II scanner and drive for a few days. If the code does not return, your gas cap probably was the culprit. Of course, there is a chance your gas cap either has worn out or is not compatible with your EVAP system.

How do you get rid of a small EVAP leak? ›

The simplest solution is to remove and reattach the gas cap. Once you do, clear the code on the OBD-II scanner and drive for a few days. If the code does not return, your gas cap probably was the culprit. Of course, there is a chance your gas cap either has worn out or is not compatible with your EVAP system.

How do you seal an EVAP leak? ›

If there is a leak, remove and reinstall the gas cap and retest. If the leak goes away, you've found the problem. If it doesn't, remove the gas cap again. Switch to the smoke hose and fill the system with smoke until it exits the filler neck.

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