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P0455 and p0449. 08 avalanche 5.3 lt. Replaced gas cap and…

Customer Question
P0455 and p0449 Mechanic's...

P0455 and p0449

Mechanic's Assistant: What is the model/year of your Chevy?

08 avalanche 5.3 lt

Mechanic's Assistant: Are you fixing your Avalanche yourself? What have you tried so far?

Replaced gas cap and evap canister

Mechanic's Assistant: Has the vehicle turned into a gas hog? And how does it start -- same as usual?

Same as usual

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

No that's it

Submitted: 5 months ago.Category: Chevy
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Answered in 3 minutes by:
12/15/2017
Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago
Roy
Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 7,452
Experience: ASE master tech for 40 years
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hello, my name is ***** ***** I will be glad to assist you. please allow me a couple of minutes to gather some basic info.

Roy

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Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

let me get some info for you

Roy

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Customer reply replied 5 months ago
What other info is needed?
Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

nothing yet. looking up the info

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Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

455

most common failure is the vent valve at the back of the truck. looking up the 449

Roy

DTC P0455
- Evaporative Emission (EVAP) System Large Leak Detected

Circuit/System Description

The ECM tests the Evaporative Emission (EVAP) System for a large leak or restrictions to the purge path in the EVAP system. When the enabling criteria has been met the ECM commands the EVAP canister vent solenoid valve ON and the EVAP canister purge solenoid valve ON, allowing vacuum into the EVAP system. The ECM monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time.

Conditions for Running the DTC

* Before the ECM can report DTC P0455 failed, DTC P0496 must run and pass.
* DTCs P0106, P0107, P0108, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0220, P0222, P0223, P0442, P0443, P0449, P0451, P0452, P0453, P0454, P0464, P0496, P0608, P0609, P0641, P0651, P1516, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138 are not set.
* The ignition voltage is between 11-18 volts.
* The barometric pressure (BARO) is more than 74 kPa.
* The fuel level is between 15-85 percent.
* The engine coolant temperature (ECT) is less than 35°C (95°F).
* The intake air temperature (IAT) is between 4-30°C (39-86°F).
* DTC P0455 runs once per cold start when the above conditions are met.

Conditions for Setting the DTC

The EVAP system is not able to achieve or maintain a calibrated level of vacuum within a set amount of time.

Action Taken When the DTC Sets

DTC P0455 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0455 is a Type B DTC.

Diagnostic Aids

* Inspect for a loose, missing, damaged, or incorrect fuel fill cap.
* Inspect for a damaged fuel filler neck seal surface.
* A blockage or restriction in the EVAP purge solenoid valve, purge pipe, EVAP canister, or vapor pipe, can cause this DTC to set.
* The EVAP system can be filled with smoke more quickly and completely by opening the system opposite the end where the smoke is injected. For example, when injecting smoke at the service port remove the fuel fill cap, or temporarily leave the vent open, until smoke is observed, then close the system and continue testing. If using a fuel cap adapter at the filler neck, use the J 41413-VLV at the service port to allow the system to fill faster.
* To help locate intermittent leaks using the J 41413-200, move all EVAP components while observing smoke with the J 41413-SPT.
* Individual components can be isolated and tested using adapters in the J 41413-300.
* A condition may exist where a leak in the EVAP system only exists under a vacuum condition. This type of leak may be detected by using the scan tool Purge/Seal function to create a vacuum in the EVAP system and then observe the FTP parameter for vacuum decay.

Special Tools

* CH-48096 EVAP Service Access Port Tool
* GE-41415-50 Fuel Tank Cap Adapter
* J 41413-200 Evaporative Emissions System Tester (EEST)
* J 41413-300 EVAP Cap and Plug Kit
* J 41413-SPT High Intensity White Light
* J 41413-VLV EVAP Service Port Vent Fitting

Circuit/System Testing

Important:
* Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize.

* Refer to the J 41413-200 operation manual for detailed instructions in Evaporative Emission System Diagnosis.

1. Connect the J 41413-200 to the vehicle EVAP service port. For vehicles without a service port, disconnect the purge tube at the quick connector on the EVAP canister side of the purge solenoid valve and install the CH-48096.
2. Use a scan tool to seal the EVAP system.
3. Use the flow meter on the J 41413-200, calibrated to 0.51 millimeter (0.020 inch) to determine that there is no leak in the EVAP system.

^ If a leak is detected, use the J 41413-200 to apply smoke to the EVAP system at the service port or the purge tube until the leak is located using the J 41413-SPT.

4. To test for a restriction in the purge path, connect the J 41413-200 nitrogen/smoke hose to the J 41413-311 brass cone adapter. Disconnect the hose at the fuel cap end of the GE-41415-50. Connect the J 41413-311 to the disconnected hose on the GE-41415-50. Install the GE-41415-50 filler neck end only to the vehicle.
5. Allow the engine to idle.
6. Use the Purge/Seal function to seal the system with a scan tool.
7. Command the EVAP canister purge solenoid valve to 30 percent.
8. The vacuum/pressure gage on the J 41413-200 and the FTP parameter on the scan tool should both show vacuum.

^ If the vacuum/pressure gage shows vacuum, but the FTP parameter does not show vacuum, replace the FTP sensor.
^ If neither the FTP parameter nor the vacuum/pressure gage shows vacuum, repair the restriction in the purge path.

9. Verify that the vacuum increases to the abort limit on the scan tool or more than 3.2 volts, and the values are similar between the scan tool and the vacuum/pressure gage on the J 41413-200.

^ If the values are not similar, or the voltage did not reach 3.2 volts, replace the FTP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests

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Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

the 449 is also related to the vent valve as well. I would start by inspecting the valve and the connector to be sure it is connected and not damaged

Roy

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Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

do you need any other help???

Please take a moment and rate my service 3 stars or better. that is the only way the site will pay me for my efforts.

Roy

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Customer reply replied 5 months ago
I’ve have the vent changed under the truck by the gas tank and the issue was not resolved.
Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

did you verify power to the solenoid and make sure it works on command with a scan tool???

Roy

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Customer reply replied 5 months ago
it was tested and worked
Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

did the evap monitor set???

after the repair, did you clear the code and drive it a few days??? it has to fail its internal test 3 times for the code to set. it could take several days for it to reset

Roy

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Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

any update???

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Chevy Mechanic: Roy, import/domestic specialest replied 5 months ago

do you still need help???

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