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For 1990-2009 cars only

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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

Go to Diagnostic System Check - Vehicle

2

Inspect the evaporative emission (EVAP) system for the following conditions:

    • A loose, incorrect, missing, or damaged fuel fill cap
    • A damaged EVAP purge solenoid

Did you find and correct the condition?

--

Go to Step 7

Go to Step 3

3

  1. Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle.
  2. Inspect the EVAP system for the following conditions:
  3. • Any disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses
    • A damaged EVAP canister, line or fitting.

Did you find and correct the condition?

--

Go to Step 7

Go to Step 4

4

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.

  1. Remove the fuel fill cap and install the J 41415-30 Fuel Tank Cap Adapter.
  2. Connect the nitrogen/smoke supply hose of the J 41413-200 Evaporative Emission System Tester (EEST) to the correct fuel tank cap adapter.
  3. Perform the following action as applicable:
  4. • FWD--Disconnect the EVAP filter hose, inlet side, at the 13 mm (0.5 in) diameter steel vent pipe. The EVAP filter hose has a quick connect fitting. Refer to Evaporative Emission Canister Filter Replacement.
    • AWD--Disconnect the air inlet hose at the EVAP canister. The air inlet hose has a quick connect fitting. Refer to Evaporative Emission Canister Filter Replacement.
  5. Use the remote switch to introduce smoke into the EVAP system.
  6. Continue to introduce smoke for approximately 1 minute.
  7. Turn the nitrogen/smoke valve on the control panel to NITROGEN.
  8. Use the remote switch to introduce Nitrogen gas into the EVAP system for 60 seconds.
  9. Continue to introduce smoke, then Nitrogen, at 60 second intervals, until smoke is seen exiting the open EVAP filter hose with FWD, or the canister air inlet port with AWD.
  10. Perform the following action as applicable:
  11. • FWD--Plug the open end of the EVAP filter hose with the J 41413-324 adapter from the J 41413-300 EVAP Cap and Plug kit.
    • AWD--Plug the open air inlet port of the EVAP canister with the J 41413-323 adapter from the J 41413-300 EVAP Cap and Plug kit.
  12. With the system now sealed, again introduce smoke, then Nitrogen, at 60 second intervals, while searching for exiting smoke.
  13. Inspect the entire EVAP system for exiting smoke with the J 41413-SPT High Intensity Lamp.

Did you locate and repair a leak source?

--

Go to Step 7

Go to Step 5

5

  1. Remove the fuel tank adapter from the fuel fill pipe.
  2. Observe the fuel tank pressure (FTP) sensor with a scan tool.

Is the FTP sensor voltage within the specified range?

3.5-3.8 V

Go to Step 6

Go to DTC P0451

6

  1. Remove the EVAP canister from the vehicle. Refer to Evaporative Emission Canister Replacement.
  2. Test the operation EVAP canister and EVAP vacuum leak pump assembly. Refer to Evaporative Emission Control System Diagnosis.

Did the EVAP components pass all tests?

--

Go to Step 7

Go to Step 10

7

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.

  1. Remove the fuel fill cap and install the J 41415-30 Fuel Tank Cap Adapter.
  2. Connect the nitrogen/smoke supply hose of the J 41413-200 Evaporative Emission System Tester (EEST) to the correct fuel tank cap adapter.
  3. Perform the following action as applicable:
  4. • FWD--Disconnect the EVAP filter hose, inlet side, at the 13 mm (0.5 in) diameter steel vent pipe and plug the open end of the hose with the J 41413-324 adapter from the J 41413-300 EVAP Cap and Plug Kit.
    • AWD--Disconnect the air inlet hose at the EVAP canister and plug the canister port with the J 41413-323 adapter from the J 41413-300 EVAP Cap and Plug Kit.
    • Both the FWD and AWD hoses have a quick connect fitting. Refer to Evaporative Emission Canister Filter Replacement.
  5. Turn the nitrogen/smoke valve to NITROGEN.
  6. Pressurize the EVAP system until the flow gage indicator on the EEST has dropped to a no flow position.
  7. Observe the flow gage for 5 minutes.

Did the flow gage indicator remain in the no flow position?

--

Go to Step 9

Go to Step 8

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

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  4. Perform the EVAP service bay test with the scan tool. Refer to EVAP Service Bay Test in Service Bay Test.

Are there any EVAP DTCs set in Last Test Failed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

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?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK