The P0456 diagnostic trouble code (DTC) pertains to a small leak in the Evaporative Emissions Control (EVAP) system. This is all part of the powertrain system, which works to keep fuel vapors from being expelled into the atmosphere. Instead, the vapors are returned to the engine and burned off. This code is universal and applies to a lot of vehicles, including Dodge, Ford, and Hyundai models, but the exact repair procedures may vary by make and model.
Potential Symptoms
In a typical case there will not be any symptoms other than the Malfunction Indicator Lamp (MIL) — or Check Engine Light.
Because the EVAP system only addresses fuel vapors, not engine management, the engine performance may not be affected unless the leak is significant.
Common Causes
Damaged gas cap: the most common reason for this code. The cap may be cracked, worn, or not properly tightened.
Fueling with Engine Running: This code can also come up if the fuel tank is filled with the engine on.
Small Leaks in EVAP Hoses or Fuel Tank Hoses: Any of these hoses can develop a pinhole or crack leak.
Defective Purge or Vent Valve: These components can wear or fail over time.
Faulty EVAP Canister: The canister is where the vapors of fuel are stored and can be a reason this code appears if it is malfunctioning.
P0456 Diagnostic and Repair Steps
Scan Tool Diagnosis:
(replace vent solenoid and seal system using scan tool) Check the Fuel Tank Pressure (FTP) sensor reading As long as the system is sealing correctly, the reading from the sensor should remain stable. If there is a leak, the sensor will give a value that is variable or misguided.
Smoke Testing:
Test the EVAP system using a smoke machine. It also helps customers detect leaks in hoses, valves, or other components by watching where smoke billows out. Therefore, the faulty part will be the leaking area.
Component Inspection:
Check the gas cap, hoses, valves, and canister for visible damage or wear.
Fit the Wrong Puzzles Pieces Together:
This does make sense, as most techs check for leaks using air pressure, but beware – this can damage sensors such as purge and vent solenoids, resulting in worse problems later down the road.
Resolving a P0456 code involves a thorough inspection of the EVAP system, given the code’s focus — fuel vapor containment. Then check to see if the gas cap is loose (and tighten it if necessary). If not, perform smoke testing and check all associated components including hoses and valves. Overpressurizing the system isn’t advisable either, and can create more damage.