What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles. Although generic, specific repair steps may vary by make/model.
The Powertrain Control Module (PCM) performs various tests on the EVAP system at different times. Enhanced OBD II EVAP systems are designed to prevent fuel tank vapors from escaping into the atmosphere and instead purge them into the engine to be burned.
Regular pressure tests are performed by the PCM to monitor the sealed system for leaks. The PCM monitors the EVAP system pressure by observing the Fuel Tank Pressure (FTP) sensor. When the sensor indicates a small leak in the EVAP system, this code is set.
Evaporative emission related trouble codes include P0450, P0451, P0452, P0453, P0454, P0455, P0457, P0458, and P0459.
Symptoms
potential
There will likely be no noticeable symptoms other than the Malfunction Indicator Lamp (MIL). This is because the EVAP system is a closed system and only controls fuel tank vapors, not engine management.
Causes
Usually, this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could also trigger this code, or if the cap was not properly tightened. One of the following could also be the cause:
A small leak in one of the EVAP hoses or fuel tank lines
A small leak in the purge valve or vent valve
The EVAP canister has a small leak
Possible Solutions
First, using a scan tool, activate the vent solenoid, sealing the system. Then monitor the Fuel Tank Pressure (FTP) sensor. If the system seals properly, the reading will remain constant. If not, the pressure sensor will show this. If the system is leaking slowly, use a smoke machine and watch for smoke escaping from the system at an EVAP component. Anywhere smoke is escaping from the system indicates the faulty component. Do not pressurize the EVAP system with air. This could damage the system’s purge and vent solenoids.
Other EVAP DTCs: P0440 – P0441 – P0442 – P0443 – P0444 – P0445 – P0446 – P0447 – P0448 – P0449 – P0452 – P0453 – P0455