Technical Description of OBD-II Trouble Code
A small leak has been detected in the Evaporative Emissions System.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The Powertrain Control Module (PCM) performs various tests on the EVAP system at different times. Enhanced EVAP systems are designed to prevent fuel tank vapors from venting into the atmosphere. Instead, the vapors are purged into the engine to be burned.
The PCM conducts regular pressure tests to monitor the sealed system for leaks. It 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 triggered.
Other related trouble codes for evaporative emissions include P0450, P0451, P0452, P0453, P0454, P0455, P0457, P0458, and P0459.
Potential Symptoms
There are usually no noticeable symptoms other than the Malfunction Indicator Lamp (MIL) illuminating. This is because the EVAP system is a closed system that only controls fuel tank vapors, not engine management.
Causes
Typically, this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running or not properly tightening the cap could also cause this code. Other possible causes include:
Possible Solutions
First, use a scan tool to activate the vent solenoid and seal the system. Then monitor the fuel tank pressure (FTP) sensor. If the system is sealing properly, the pressure reading will remain consistent. If it is not sealing properly, the pressure sensor will indicate a problem. If the system is slowly leaking, use a smoke machine to detect smoke exiting the system at any EVAP component. The faulty component will be where the smoke is observed. Do not pressurize the EVAP system with air pressure, as this can damage the purge and vent solenoids.
Other EVAP DTCs: P0440 – P0441 – P0442 – P0443 – P0444 – P0445 – P0446 – P0447 – P0448 – P0449 – P0452 – P0453 – P0455
