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P1456 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

Evaporative Emission Control System Leak

Meaning

EVAP control system in the engine, and the computer of the vehicle has detected this leak. This means there is a fuel vapor leak or a failure to purge it from the engine. P1xxx is a manufacturer-specific error code, just like other codes beginning with that number. There may be differences between vehicle brands in the diagnosis and repair of this error code

Causes

  • Fuel cap is missing
  • Use of the wrong fuel filler cap
  • Cap does not close or remains open during fuel fill-up
  • Objects stuck in fuel filler cap
  • Purging solenoid for EVA
  • Canisters used for EVAP
  • Pressure sensor for fuel tanks

Symptoms

  • Engine check light is on
  • There is an odor of fuel vapor caused by the leak
  • A lack of drivability and poor vehicle performance does not exist

Diagnosis

When the Fuel Tank Pressure Sensor detects leaking fuel in the tank, this code denotes that the EVAP system is not making a sufficient vacuum when doing its leak test.

EVAP leak tests are conducted by the PCM as follows.

  • It is necessary for the vehicle to have been sitting at least four hours, overnight, before the leak test can be performed. The purpose is to cool the engine down so it is at the same temperature as the surrounding area. A good baseline for testing is to also have fuel (between 15% and 85%) in the tank since gasoline and diesel fuel are both volatile fluids that easily expand and vaporize at warm temperature.
  • In order to prevent any outside air from entering the EVAP system, vent valves on vapor canisters will close when the leak test starts.
  • When the Purge Valve activates, the engine makes a vacuum in the Evaporative Emissions System.
  • The Fuel Tank Pressure Sensor can measure the level of vacuum in the system after the Purge Valve shuts itself off after 10 seconds
  • There will be a countdown starting to check the vacuum decay rate in the system. The PCM will fail the EVAP system automatically if vacuum is not reached after two consecutive tests, or if there is no vacuum after two consecutive tests. This will lead to the P1456 error code, which indicates a gross leak.

How serious is this?

The check engine light will not go out even if the gas cap is in place and tight. You are most likely dealing with another issue or a faulty gas cap. I believe the best way to diagnose a problem is not to pull a code and guess what the cause is, but to find a shop or dealership with the necessary equipment to do so. Diagnose tools are available at dealers that can check the emission system; these tools can run the evaporative test without requiring the driver to drive the car. 

Time and money can be saved if you have the right mechanic to do the job. In most small shops, the mechanics do not have access to the right tools, and they generally won't spend the money on more expensive tools. The manufacturer forces dealers to spend the money so that they can be competitive. There is a reason why dealerships charge more than small mechanic shops, but they have the right tools and the right information to repair your vehicle, but you still need to find the right mechanic.

What repairs can fix the code?

You can fix your vehicle using some of the following methods:  

  • The gas cap must be removed from the filler neck and reinstalled properly and tightly onto the filler neck. Check the error code again using the scan tool after the code reader has been cleared and the car has been driven for a day.
  • Make sure the gas cap is replaced if necessary.
  • Look for leaking, cut, and holes on the EVAP tube and hose. Perform repairs if you notice vacuum noise or scent fuel vapor.

Related codes

None listed.

Conclusion

If you have a fuel vapor leak, you might be in luck, as there are three ways to go about fixing it. If you have a local, trusted mechanic, you'll save yourself time and money. If you don't, you might want to take your car to a dealership or manufacturer. If you do decide to take your car to a dealership, ask the mechanics about what they'll do before you bring it in.