GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Epica 🢒 DTC 🢒 DTC P0442 or P0456

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptors

DTC P0442 :  Evaporative Emission (EVAP) System Small Leak Detected

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

Circuit Description

The evaporative emission (EVAP) small leak test applies vacuum to the EVAP system and monitors vacuum decay. The control module monitors the fuel tank pressure sensor signal to determine the vacuum decay rate. At an appropriate time, the EVAP canister purge valve and the EVAP vent valve are turned ON. This allows the engine to draw vacuum on the EVAP system. After the desired vacuum level has been achieved, the EVAP purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level during a given time period.

FTP Sensor Signal Voltage

Fuel Tank Pressure

High, Approximately 1.5 Volts or More

Negative Pressure/Vacuum

Low, Approximately 1.5 Volts or Less

Positive Pressure

Conditions for Running the DTC
    • DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0137, P0138, P0140, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, P0277, P0300, P0402, P0404, P0405, P0406, P0452, P0453, P0462, P0463, P0501, P1449, and P2422 are not set.
    • The ignition 1 voltage is between 11-16 volts.
    • The barometric pressure (BARO) is greater than 72 kPa.
    • The engine coolant temperature (ECT) is greater than 70°C (158°F).
    • The estimated ambient air temperature is greater than 10°C (50°F).
    • The purge enable time is greater than 15 seconds.
    • The engine run time is greater than 590 seconds.
    • The fuel tank pressure is greater than -7.50 mmHg (-1 inch H2O) and less than +2.25 mHg (+1.2 inch H2O).
    •  The vehicle speed is less than 2 km/h (1 mph).
    • The engine is idling.
    • The DTCs run once an ignition cycle when the above conditions are met.

Conditions for Setting the DTC

The EVAP system can achieve vacuum, but a vacuum decay is detected during the diagnostic test.

Action Taken When the DTC Sets

DTC P0442 is a Type A/B DTC.

DTC P0456 is a Type A/B DTC.

Conditions for Clearing the DTC

DTC P0442 is a Type A/B DTC.

DTC P0456 is a Type A/B DTC.

Diagnostic Aids
    • To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT High Intensity White Light.
    • 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 . Introducing smoke in 15 second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a greater condensed manner.
    • Observe the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set . This may assist in diagnosing the condition.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Description and Operation:

Evaporative Emission Control System Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Special Tools Required

    • J 41413-SPT High Intensity White Light
    • J 41413-VLV EVAP Port Vent Fitting Tool
    • J 41413-200 Evaporative Emissions System Tester (EEST)
    • J 41413-300 EVAP Cap and Plug Kit
    • GE-41415-50 Fuel Tank Cap Adapter
    • J 23738-A Hand Vacuum Pump

Circuit/System Verification
  1. Verify the following conditions do not exist in the EVAP system:
    2. • Loose, incorrect, missing, or damaged fuel fill cap
    • Loose, missing, or damaged service port schrader valve
    • A damaged EVAP purge solenoid
    • Disconnected, incorrectly routed, kinked, or damaged EVAP pipes and hoses
    • A damaged EVAP vent valve or EVAP canister
         ⇒If you find any of the above conditions, repair as necessary.

    Important: Refer to the J 41413-200 operation manual for detailed instructions.

  2. Remove the fuel fill cap. Connect the GE-41415-50 to the fuel tank filler neck. Connect the J 41413-200 to the GE-41415-50 .
  3. Calibrate the J 41413-200 Flow Meter to the correct leak orifice for the vehicle.
  4. Disconnect the EVAP vent line from the vent solenoid and seal it, using a suitable plug from the J 41413-300 .

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

  5. Activate the J 41413-200 and compare the flow meter's stable floating indicator position to the red flag. The floating indicator should be at or below the red flag.
    6. ⇒If above the red flag, test for a leak in the EVAP system.
  6. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

    Important: 

       • You must start with the Circuit/System Verification before proceeding with Circuit/System Testing.
       • 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.
       • Refer to the J 41413-200 operation manual for detailed instructions.

  1. Remove the fuel fill cap. Connect the GE-41415-50 to the fuel tank filler neck. Connect the J 41413-200 to the GE-41415-50 .
  2. Turn the nitrogen/smoke valve on the control panel to SMOKE.
  3. Disconnect the EVAP vent line from the vent solenoid and seal it, using a suitable plug from the J 41413-300 .
  4. Use the remote switch to introduce smoke into the EVAP system.
  5. Use the J 41413-VLV to open the EVAP service port. Once smoke is observed, remove the tool.

    6. Important: Introduce smoke at 15 second intervals while testing the system.

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

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

    ⇒If smoke is observed, repair the condition as necessary.
  7. Test the EVAP system using the EVAP service port. Connect the J 41413-200 nitrogen/smoke supply hose to the EVAP service port.
  8. Use the remote switch to introduce smoke into the EVAP system.
  9. Verify that smoke is not exiting the entire EVAP system with the J 41413-SPT .
    10. ⇒If smoke is observed, repair the condition as necessary.
  10. Test the individual EVAP system components for a leak using the J 41413-300 . Verify the EVAP system components do not leak.
    11. ⇒If a condition is found replace the affected component.

Component Testing
  1. Remove the EVAP vent solenoid.
  2. Connect the vent solenoid electrical terminals to B+ and ground.
  3. Connect the J 23738-A to a vacuum port on vent solenoid. Apply and hold a vacuum of 10 inches for 30 seconds.
    4. ⇒If a vacuum cannot be obtained and held as specified, replace the EVAP vent solenoid.

Repair Instructions

Evaporative Emission Canister Purge Solenoid Valve Replacement

Repair Verification
  1. Remove the fuel fill cap. Connect the GE-41415-50 to the fuel tank filler neck. Connect the J 41413-200 to the GE-41415-50 .
  2. Disconnect the EVAP vent line from the vent solenoid, and seal it, using a suitable plug from the J 41413-300 .
  3. Turn the nitrogen/smoke valve to nitrogen.
  4. Use the remote switch to introduce nitrogen and fill the EVAP system until the floating indicator stabilizes.
  5. Verify the flow meter's stable floating indicator position is at or below the red flag.
  6. Clear the DTCs with a scan tool.