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 in order 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 more than 5 hours and the engine coolant temperature is less than 35°C (95°F), a comprehensive diagnostic is enabled. The complete diagnostic test can take up to 15 minutes to run, with leak detection comprising the largest portion of the test. The DTC P0455 diagnostic detects evaporative emission system leaks as small as 1.0 mm (0.040 in) and the P0456 diagnostic detects leaks as small as 0.51 mm (0.02 in).

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves.

P0455

The specified minimum value of vacuum pressure was not obtained.

P0456

The specified minimum value of vacuum pressure cannot be maintained for the specified minimum length of time.

DTC P0455 and P0456 are Type B DTCs.

DTC P0455 and P0456 are Type B DTCs.

Schematic Reference

Evaporative Emissions Hose Routing Diagram

Description and Operation

Evaporative Emission Control System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

With Service Bay Test

1. Verify the EVAP system using the EVAP Service Bay Test, refer to Service Bay Test. DTC P0455 or P0456 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Without Service Bay Test

Important: 

•	The EVAP vent solenoid DOES NOT have to be activated in order to perform this test.

•	Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. The system flow will be less with higher temperatures.

1. Connect the J 41415-30 to the fuel tank filler neck. Connect the J 41413-200 to the J 41415-30 .
2. Turn the nitrogen/smoke valve to nitrogen.
3. Use the remote switch to introduce nitrogen and fill the EVAP system until the floating indicator stabilizes.
4. Verify the flow meter's floating indicator position is stable and at or below the red flag for 5 minutes.

Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0441 is not set.

Leak Testing P0455 and P0456

1. Verify the following conditions do not exist in the EVAP system:

•	Loose, incorrect, missing, or damaged fuel fill cap

•	A damaged EVAP purge solenoid

•	Disconnected, incorrectly routed, kinked, or damaged EVAP pipes and hoses

•	A damaged EVAP canister, lines, or fittings

⇒	If you find any of the above conditions, repair as necessary.

Important: 

•	The EVAP vent solenoid DOES NOT have to be activated in order to test for leaks.

•	Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. The system flow will be less with higher temperatures.

2. Connect the J 41415-30 to the fuel tank filler neck. Connect the J 41413-200 to the J 41415-30 .

Important: Leaving the EVAP filter hose disconnected speeds up the filling of the canister and fuel tank with smoke. Waiting until smoke is seen exiting the open EVAP filter hose before plugging the hose shortens leak testing diagnostic time.

3. 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 EVAP Canister Filter Replacement for the quick connect fitting servicing procedure.
4. Turn the nitrogen/smoke valve on the control panel to SMOKE. Use the remote switch to introduce smoke into the EVAP system.
5. Continue to introduce smoke for approximately 1 minute.
6. Turn the nitrogen/smoke valve on the control panel to NITROGEN. Use the remote switch to introduce Nitrogen gas into the EVAP system for 60 seconds.

Important:  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 more 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.

7. Continue to introduce smoke, then Nitrogen, at 60 second intervals, until smoke is seen exiting the open EVAP filter hose.

Important: The installation of the adapter J 41413-323 or J 41413-324 seals the tank side of the EVAP system.

8. Plug the open end of the EVAP filter hose with the J 41413-323 or J 41413-324 adapter from the J 41413-300 .
9. With the system now sealed, again introduce smoke, then Nitrogen, at 60 second intervals.

Important: The fuel tank may need to be lowered to improve visibility of some of the EVAP system components.

10. Verify that smoke is not exiting the entire EVAP system with the J 41413-SPT .

⇒	If smoke is observed, repair the condition as necessary.

Additional Leak Testing P0456 Only

1. Turn the nitrogen/smoke valve to nitrogen.
2. Use the remote switch to introduce nitrogen and fill the EVAP system until the floating indicator stabilizes.
3. Verify the flow meter's floating indicator position is stable and at or below the red flag for 5 minutes.

⇒	If the floating indicator moves above the red flag, test the fuel tank for leaks. Refer to Fuel Tank Leak Test.

Blockage/Restriction Testing

1. Verify the following conditions do not exist in the EVAP system:

•	A plugged or restricted EVAP filter

•	A plugged or restricted air inlet pipe or hose

⇒	If a condition is found repair or replace the affected component.

Important: The EVAP canister assembly contains passages and internal valves that need to be tested for blockage and restrictions.

2. Test the operation of the EVAP canister and EVAP vacuum leak pump assembly. Refer to Evaporative Emission Control System Diagnosis.

⇒	If a condition is found replace the affected component.

Important: This test verifies the function of the FTP sensor. An inaccurate FTP sensor signal can set an EVAP system leak DTC.

1. Ignition ON, remove the J 41415-30 from the fuel tank filler neck. Observe that the FTP sensor scan tool parameter is 3.5-3.8 volts.

⇒	If the FTP sensor reading is not within the specified range, refer to DTC P0451.

2. Test the operation of the EVAP canister and EVAP vacuum leak pump assembly. Refer to Evaporative Emission Control System Diagnosis.

⇒	If a condition is found replace the affected component.

With Service Bay Test

Verify the EVAP system repair using the EVAP Service Bay Test. Refer to Service Bay Test.

Without Service Bay Test

1. Connect the J 41415-30 to the fuel tank filler neck. Connect the J 41413-200 to the J 41415-30 .
2. Turn the nitrogen/smoke valve to nitrogen.
3. Use the remote switch to introduce nitrogen and fill the EVAP system until the floating indicator stabilizes.
4. Verify the flow meter's floating indicator position is stable and at or below the red flag for 5 minutes.