P0456 Evaporative Emission System Leak Detected (Very Small Leak)
The PCM monitors the Evaporative Emission (EVAP) System pressure.
The PCM controls the evaporative emission ventilation solenoid. It closes the evaporative emission ventilation solenoid to seal the evaporative emission canister side of the system.
The evaporative emission purge solenoid is opened to allow manifold vacuum to create low pressure (vacuum) in the EVAP system.
When the EVAP system develops a vacuum of 2 kPa (0.29 psi), the evaporative emission purge solenoid is closed and the fuel system vacuum is maintained at 2 kPa (0.29 psi).
The PCM determines whether there is a leak in the EVAP system by monitoring the vacuum inside the fuel tank.
The test is stopped when fuel vapor pressure exceeds predetermined limits.
DTC SET CONDITIONS
Test Conditions:
Fuel level sensor output voltage is 2.4 − 3.7 volts when the engine is started, and the amount of remaining fuel is 40 − 85 percent of capacity.
Engine coolant temperature is less than 36°C (97°F) when the engine is started.
Intake air temperature is less than 36°C (97°F) when the engine is started.
Engine coolant temperature is greater than 20°C (68°F).
Intake air temperature is greater than −10°C (14°F).
Fuel tank temperature is less than 33°C (91°F).
Barometric pressure is greater than 76 kPa (11 psi).
Fuel tank differential pressure sensor output voltage is 1 − 4 volts.
When the evaporative emission purge solenoid and evaporative emission ventilation solenoid are closed, the pressure rises in the fuel tank is less than 324 Pa (0.047 psi).
10 seconds have elapsed from the start of the previous monitoring.
Monitoring time: 10 − 14 seconds.
Judgment Criteria:
Internal pressure of the fuel tank has changed greater than 1,177 − 1,373 Pa (0.171 − 0.199 psi) in 128 seconds after the tank and vapor line were closed.
Only one monitor during one drive cycle.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Loose fuel cap.
- Fuel cap relief pressure is incorrect.
- Evaporative emission canister seal is leaking.
- Fuel tank, purge line or vapor line seal is leaking.
- Evaporative emission ventilation solenoid does not seal.
OVERVIEW OF TROUBLESHOOTING
To determine the cause of DTC P0456, a performance test is needed. The performance test uses a mechanical vacuum gauge and scan tool MB991502 set to the data reading mode for the fuel tank differential pressure sensor (TANK
PRES SNER 73). The mechanical gauge reading is used to verify the scan tool reading. A comparison of the mechanical gauge and scan tool MB991502 determines whether there is problem in the system.
Prior to doing the performance test, ensure that the fuel cap is closed securely. Inspect all EVAP system hoses and tubes for damage.
The PCM monitors the Evaporative Emission (EVAP) System pressure.
The PCM controls the evaporative emission ventilation solenoid. It closes the evaporative emission ventilation solenoid to seal the evaporative emission canister side of the system.
The evaporative emission purge solenoid is opened to allow manifold vacuum to create low pressure (vacuum) in the EVAP system.
When the EVAP system develops a vacuum of 2 kPa (0.29 psi), the evaporative emission purge solenoid is closed and the fuel system vacuum is maintained at 2 kPa (0.29 psi).
The PCM determines whether there is a leak in the EVAP system by monitoring the vacuum inside the fuel tank.
The test is stopped when fuel vapor pressure exceeds predetermined limits.
DTC SET CONDITIONS
Test Conditions:
Fuel level sensor output voltage is 2.4 − 3.7 volts when the engine is started, and the amount of remaining fuel is 40 − 85 percent of capacity.
Engine coolant temperature is less than 36°C (97°F) when the engine is started.
Intake air temperature is less than 36°C (97°F) when the engine is started.
Engine coolant temperature is greater than 20°C (68°F).
Intake air temperature is greater than −10°C (14°F).
Fuel tank temperature is less than 33°C (91°F).
Barometric pressure is greater than 76 kPa (11 psi).
Fuel tank differential pressure sensor output voltage is 1 − 4 volts.
When the evaporative emission purge solenoid and evaporative emission ventilation solenoid are closed, the pressure rises in the fuel tank is less than 324 Pa (0.047 psi).
10 seconds have elapsed from the start of the previous monitoring.
Monitoring time: 10 − 14 seconds.
Judgment Criteria:
Internal pressure of the fuel tank has changed greater than 1,177 − 1,373 Pa (0.171 − 0.199 psi) in 128 seconds after the tank and vapor line were closed.
Only one monitor during one drive cycle.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Loose fuel cap.
- Fuel cap relief pressure is incorrect.
- Evaporative emission canister seal is leaking.
- Fuel tank, purge line or vapor line seal is leaking.
- Evaporative emission ventilation solenoid does not seal.
OVERVIEW OF TROUBLESHOOTING
To determine the cause of DTC P0456, a performance test is needed. The performance test uses a mechanical vacuum gauge and scan tool MB991502 set to the data reading mode for the fuel tank differential pressure sensor (TANK
PRES SNER 73). The mechanical gauge reading is used to verify the scan tool reading. A comparison of the mechanical gauge and scan tool MB991502 determines whether there is problem in the system.
Prior to doing the performance test, ensure that the fuel cap is closed securely. Inspect all EVAP system hoses and tubes for damage.