DTC Advanced Diagnostics: P0456
DTC P0456:Evaporative Emission (EVAP) System Very Small Leak Detected

General Description

The powertrain control module (PCM) starts the evaporative emission (EVAP) system diagnosis after the vehicle has been turned to the OFF (LOCK) mode, and has met all other enable conditions (initial engine coolant temperature [ECT SENSOR 1] and off for at least 5 hours). The EVAP system diagnosis is performed by reducing pressure between the EVAP canister and the atmosphere. If pressure is reduced with the fuel vapor containment valve open, the entire EVAP system will be diagnosed, and if the fuel vapor containment valve is closed, only the EVAP canister side will be diagnosed.

EVAP leak detection module operation flow
Reference pressure measurement : Malfunction detection in the EVAP leak check module itself and determination of early completion of pressure reduction when normal.
System pressure reduction : Pressure in the EVAP system is reduced to measure the ultimate pressure.
Reference pressure re-measurement : Leak is detected by comparing with the ultimate pressure of the system pressure reduction.
Reference value is to be measured twice considering change in the characteristics of the vacuum pump during detection.

Reference pressure is the pressure reduction by the reference orifice (#40 equivalent ) in the EVAP leak check module used to check for leak by comparison with the system pressure reduction.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Once per driving cycle
Sequence
P0455 is judged as OK
Duration
At least 10 minutes but not more than 18 minutes 45 seconds
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Elapsed time after turn the vehicle to the ON mode
10 minutes
–
Elapsed time after turn the vehicle to the OFF (LOCK) mode
5 hours
–
PCM wake upengine coolant temperature [ECT SENSOR 1]
40 °F (5 °C)
95 °F (35 °C)
Barometric pressure
[BARO SENSOR]
76 kPa (569 mmHg, 22.5 inHg)
–
Battery voltage
[BATTERY]
10.5 V
–
Other
No refueling is required
[ ]: HDS Parameter

Malfunction Threshold
Either of these conditions occurs:

When the fuel tank internal pressure is not near the barometric pressure.

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
EVAP system leak (EVAP canister purge valve from fuel tank)

Confirmation Procedure
Operating Condition
1.
With the engine coolant temperature [ECT SENSOR 1] within the specified range, turn the vehicle to the ON mode, and wait for at least 10 minutes.
2.
Turn the vehicle to the OFF (LOCK) mode, and wait for at least 5 hours.
3.
PCM wake up, and wait at least 18 minutes, 45 seconds.
With the HDS
Select the EVAP TEST in the INSPECTION MENU, then select the FUNCTION TEST with the HDS.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle with the engine coolant temperature and intake air temperature at engine start-up within the specified temperature range, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle with the engine coolant temperature and intake air temperature at engine start-up within the specified temperature range, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.