P0456 Code – What It Means and How To Fix It

A guide of how to diagnose & repair problems causing the P0456 trouble code

P0456 Code

The P0456 trouble code appears in your engine control unit when there is a small leak in your EVAP system.

There can be many reasons why this happens, and in this guide, you will find out everything you have to know about the P0456 code.

Code P0456 Definition

Evaporative Emissions System – Small Leak Detected

What does the P0456 code mean?

The P0456 code indicates that there is a small leak in the evaporative emissions system. The EVAP system is a sealed system that controls the fuel vapors from the gas tank, which recycles the fuel vapors through the engine instead of letting them out into the environment.

P0456 Trouble Code Symptoms

You will most likely not notice any symptoms of the p0456 code except a check engine light on your dashboard. In rare cases, you can also notice a fuel smell coming from the engine.

  • Check Engine Light
  • Gasoline Smell

Causes of the P0456 Code

The p0456 code is often caused because the driver did not shut off the engine while refueling it. It can also be caused by a not properly tightened fuel cap, or the fuel cap might be leaking.

  • Driver error
  • Not tightened Gas Gap
  • Leaking Gas Cap
  • Leaking EVAP vacuum hose
  • Faulty EVAP control purge valve
  • Leaking fuel tank
  • Leaking charcoal canister

How serious is the P0456 Code?

Very Low – You will not notice any driveability problem in your car when the P0456 code appears.

The only thing that could happen is that the emission system is not working properly when the Check Engine light is illuminated on your dashboard. This means that even if it is not serious to your engine, you should not wait to repair the fault causing the P0456 code.

What repairs can fix the P0456 code?

  • Tightening the gas cap and clear trouble codes
  • Replace gas cap
  • Repair leaking EVAP hoses
  • Replace EVAP control purge valve
  • Repair wirings to EVAP control purge valve
  • Replace charcoal canister
  • Replace fuel tank

Common P0456 Diagnosis mistakes

The most common diagnosis mistake of the P0456 code is to start doing advanced troubleshooting. The P0456 code is often just caused by driver error, which means that there may be no problem with the vehicle.

Just make a quick inspection of the hoses and the purge valve and ask the customer if they were refueling without shutting the engine off.

Recommended Tools for Diagnosis

  • Diagnostic OBD Scan Tool
  • Multimeter
  • Basic Hand Tools
  • EVAP Smoke Machine
  • Auto Repair Manual
  • Electrical Contact Cleaner

How to diagnose the P0456 Trouble Code

In most cases, you do not have to diagnose the p0456 code in other ways than just tightening the gas cap and clearing the trouble codes. Here is what you should do if the trouble code comes back.

  1. Connect an OBD2 scanner and look for related trouble codes. Find information about them and check if it can lead you somewhere in the troubleshooting.
  2. Check for any leaks visually.
  3. Connect an EVAP smoke machine and connect to the EVAP system. Look for any leaks around the vacuum hoses or at the gas tank, and repair any leaks you find.
  4. Disconnect the EVAP purge valve plug, make an output test from the engine control unit to the EVAP purge valve with your scanner, and measure the connector plug with a multimeter. Make sure you get both 12v+ and ground.
  5. Test the purge control valve by sending 12v+ and ground to it. Test if it is closing and opening the air through it while doing so. Replace if faulty.

Estimated Cost of Repair

Here are some examples of common repairs related to the P0442 code. The prices include parts and labor. It does not include the cost of diagnosis.

  • Gas cap replacement cost – 30$ to 70$
  • EVAP purge control valve replacement – 40$ to 80$
  • EVAP hose replacement cost – 20$ to 50$

Related P0456 Trouble Codes

Common P0456 Related Questions

What causes code P0456?

The p0456 code is most often caused by a gas cap that hasn’t been properly tightened or a driver error, where the driver did not shut off the engine while refueling. It can also be caused by a leaking gas cap or a faulty EVAP control valve.

What does P0456 mean?

The p0456 code means that there is a small leak in the EVAP system. The EVAP system is a sealed system that controls the fuel vapors from the fuel tank.

How to clear code P0456?

To clear the P456 code, you need to use an OBD2 scanner. Remember that just clearing the P0456 code might not fix the problem, and it may come back sooner or later.

How to fix P0456 code?

It is often enough to make sure the gas cap is tightened and clear the trouble code to fix the P0456 code. In rare cases, you might have to replace the fuel cap or any leaking EVAP hoses.

Magnus Sellén
Written by:

Magnus is the owner and main author of Mechanicbase. He has been working as a car mechanic for over 10 years, and the majority of them specialized in advanced car diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.

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