The P1457 code can have several causes and, thus, takes some time to diagnose properly. One of the first and more common causes is a defective vent valve or vent valve solenoid. The vacuum process starts with the engine creating a small vacuum in the EVAP system that causes negative pressure, which is then converted into a varying signal voltage by the fuel tank pressure sensor. The PCM continuously monitors the fuel tank pressure (FTP) sensor for any variations in vacuum levels while the system is sealed. The outside air temperature, however, is monitored to account for evaporation of the fuel that happens naturally during this process. This slowly increases fuel tank pressure and affects the accuracy of the leak check the PCM performs.

Another common cause of the P1457 code is a defective or loose fuel filler cap or damaged vacuum lines. A damaged or corroded charcoal canister can also cause the vacuum process not to operate correctly. You also have to be wary of damaged, burnt, or corroded wiring and connectors, as these can also cause the code to set. A defective purge valve also can cause this issue if it’s stuck open, which allows for outside air to make its way into the EVAP system. This is why you’re sure to find accompanying purge valve or vapor flow and pressure codes present alongside the P1457 code. Finally, a defective fuel tank pressure sensor can cause the issue to appear.

As we mentioned, you may not notice immediate driveability symptoms with the P1457 code, but this doesn’t mean that you should continue to drive your vehicle as usual. Driving your vehicle can lead to further stresses put on your engine due to the poor air/fuel mixture present, leading to further damage of engine components. In addition, it’s never worth risking any issue that deals with vacuum lines and air and fuel mixtures because these systems have to perform regularly for your engine to operate.

The P1457 code can be very tedious to inspect since so many components are involved in the vacuum process and the EVAP system. Qualified technicians with prior experience inspecting EVAP systems should handle issues related to the P1457 code. It’s not recommended to DIY this issue because you can cause further damage to your vehicle by misdiagnosing the problem.

With that said, the technician will look to repair the vacuum lines in the EVAP system if that is what’s causing the P1457 issue. They will also repair or replace any damaged wiring or connectors leading to the charcoal canister before performing a series of tests ranging from voltage to resistance tests on the wiring in the system. The technician will check the values related to the PCM and the vent valve before making sure that the valve solenoid is receiving full voltage. They will replace the valve if the readings don’t meet the required standards.