System Description
The DTC P0456 Evaporative Emission (EVAP) System Very Small Leak Detected diagnostic detects evaporative emission system leaks as small as 0.51 mm (0.020 in). The diagnostic strategy for the EVAP system uses a vacuum pump to test for system leaks, after the engine is OFF. A unique fuel tank, EVAP canister, and EVAP vacuum leak pump work together to provide enhanced system diagnosis. The vacuum leak pump, the fuel tank pressure (FTP) sensor and the EVAP canister vent valve are all integral parts of one assembly. The assembly is attached directly to the EVAP canister, located near the fuel tank.
After the vehicle has sat with the engine OFF for at least 5 hours and the engine coolant temperature is less than 35°C (95°F), a comprehensive diagnostic is enabled. The complete test can take up to 15 minutes to run, with leak detection comprising the largest portion of the test. Once the large leak test DTC P0455 passes, the powertrain control module (PCM) will continue to monitor the FTP sensor signal in order to determine if there is small leak. If a specified minimum value is not achieved or the minimum value can not be maintained, a DTC P0456 will set. For more detailed information on the EVAP system components and diagnostic strategy, refer to Evaporative Emission Control System Description.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0456 Evaporative Emission (EVAP) System Very Small Leak Detected
Conditions for Running the DTC
| • | DTCs P0011, P0012, P0100, P0101, P0102, P0103, P0110, P0112, P0113, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0300, P0301-P0304, P0335, P0340, P0341, P0351-P0354, P0385, P043E, P043F, P0441, P0450, P0451, P0452, P0453, P0455, P0500, P2401, P2402, P2419, P2420, P2610 are not set. |
| • | Five hours have elapsed after the engine was turned Off. |
| • | Atmospheric pressure is between 70-110 kPa. |
| • | Battery voltage is more than 10.5 volts. |
| • | Engine coolant temperature is between 4-35°C (40-95°F). |
| • | Intake air temperature is between 4-35°C (40-95°F). |
| • | The ignition remains OFF for the duration of the test. |
| • | DTC P0456 runs once per drive cycle when the above conditions are met. |
Conditions for Setting the DTC
The specified minimum value of vacuum pressure was not achieved.
OR
The minimum value can not be maintained for the specified portion of the leak test.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | A DTC will clear after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool Clear Information function. |
Diagnostic Aids
| • | The EVAP control system is required to detect evaporative emission fuel system leaks as small as 0.51 mm (0.020 inch), between the fuel fill cap, and the purge solenoid. |
| • | A faulty EVAP canister can cause a DTC P0456 to set. Test the EVAP canister for internal passage leaks and restrictions. Also test the canister for the correct operation of diaphragms, check balls, and internal valves. Refer to Evaporative Emission Control System Diagnosis. |
| • | To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. |
| • | A temporary blockage in the EVAP purge solenoid, purge pipe or EVAP canister could cause an intermittent condition. Inspect and repair any restriction in the EVAP system. |
| • | In order to improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT . |
| • | Reviewing the Freeze Frame Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition. |
| • | For intermittent conditions refer to Intermittent Conditions. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Waiting until smoke is seen before plugging the EVAP canister vent line speeds up the filling of the canister and fuel tank with smoke. Introducing smoke in between 60 second intervals of Nitrogen also increases the speed of the filling of smoke in the fuel tank, the filler pipe vapor space, and the EVAP canister. This occurs because the pressure at which Nitrogen gas is applied is greater than the pressure at which smoke is introduced. The Nitrogen gas pushes the smoke that was just introduced through the canister and into the fuel tank. The EVAP vent solenoid DOES NOT have to be turned ON in order to test for leaks. The installation of the adapter J 41413-323 or J 41413-324 seals the tank side of the EVAP system.
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This test verifies that the fuel tank pressure (FTP) sensor is accurate. The FTP sensor should indicate little or no pressure with fuel fill pipe open. An FTP sensor that does not correctly respond to vacuum, or pressure may cause this DTC to set.
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This step tests the operation of the EVAP vent solenoid located in the EVAP vacuum leak pump assembly. If the vent solenoid passage leaks, the EVAP system leak diagnostic will fail and set a DTC. This internal leak is not detected using the J 41413-200 EEST.
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This step verifies whether a leak in the EVAP system still exists. If the flow gage on the EEST and/or the scan tool pressure reading remain constant, there is no external leak. If the EEST gage indicates flow, or the scan tool pressure reading decreases, there is still an external leak in the EVAP system.
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This step tests the fuel tank assembly for leaks with the tank removed from the vehicle. The J 41413-300 EVAP Cap and Plug Kit enables you to use smoke to test for a leak on the portions of the fuel tank that are not visible when installed in the vehicle.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Evaporative Emissions Hose Routing Diagram | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||
2 | Inspect the evaporative emission (EVAP) system for the following conditions:
Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 3 | ||||||||
3 |
Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 4 | ||||||||
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Important: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.
Did you locate and repair a leak source? | -- | Go to Step 7 | Go to Step 5 | |||||||||
Is the FTP sensor voltage within the specified range? | 3.5-3.8 V | Go to Step 6 | Go to DTC P0451 | |||||||||
Did the EVAP components pass all tests? | -- | Go to Step 7 | Go to Step 10 | |||||||||
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Important: Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.
Did the flow gage indicator remain in the no flow position? | -- | Go to Step 9 | Go to Step 8 | |||||||||
Inspect the fuel tank and component parts for leaks. Refer to Fuel Tank Leak Test. Did you find and correct a condition? | -- | Go to Step 11 | Go to Step 4 | |||||||||
9 |
Are there any EVAP DTCs set in Last Test Failed? | -- | Go to Diagnostic Aids | |||||||||
10 | Replace the EVAP vacuum leak pump. Refer to Evaporative Emission System Vacuum Leak Pump Replacement. Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||||
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||
