GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 G3 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 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 provides 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, P0116, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0300, P0402, P0404, P0405, P0406, P0443, P0451, P0452, P0453, P0454, P0461, P0462, P0463, P0464, P0488, P0498, P0499, P0502, P0506, P0507, P2110, P2195, and P2196 are not set.
    • One of the following conditions is met:
       - The ignition is off for greater than 12 hours.
       - OR
       - The start-up intake air temperature (IAT) and the start-up engine coolant temperature (ECT) are within 8°C (46°F).
    • The ignition 1 voltage is between 11-16 volts.
    • The barometric pressure (BARO) is greater than 72 kPa.
    • The start-up ECT and start-up IAT are between 4-34°C (39-93°F).
    • The start-up IAT is 3°C (37°F) less than the actual IAT.
    • The purge enable time is less than pre-determined value based on startup ECT.
    • The fuel level is between 6-93 percent.
    • The engine run time is between 1-360 seconds plus purge enable time.
    • The engine is running.
    • The vehicle speed is less than 3 km/h (2 mph).
    • The throttle position is less than 1 percent.
    • The manifold absolute pressure (MAP) sensor is steady within than 5 kPa.
    • 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 and P0456 are Type A/B DTCs.

Conditions for Clearing the DTC

DTC P0442 and P0456 are Type A/B DTCs.

Diagnostic Aids
    • A condition may exist where a leak in the EVAP system exists only under a vacuum condition. Test for this condition by using a scan tool Purge/Seal function to create a vacuum, then observe the FTP parameter for a vacuum decay.
    • 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 more 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

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

    • 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 Vacuum Pump

Circuit/System Verification w/Service Bay Test
  1. Verify the EVAP system using the scan tool EVAP Service Bay Test. DTCs P0442 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.

Circuit/System Verification w/o Service Bay Test
  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: 

       • 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.

  2. Calibrate the J 41413-200 Flow Meter to the correct leak orifice for the vehicle.
  3. 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 .

    4. Important: The EVAP vent solenoid valve will not remain closed when commanded ON with positive pressure applied to the EVAP system.

  4. Disconnect the EVAP vent line from the vent solenoid. Seal the EVAP vent using the correct 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 remain below the red flag.
  6. 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.

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.

  1. Turn the nitrogen/smoke valve on the control panel to SMOKE.

    2. Important: The EVAP vent solenoid valve will not remain closed when commanded ON with positive pressure applied to the EVAP system.

  2. Disconnect the EVAP vent line from the vent solenoid, and seal it, using the correct plug from the J 41413-300 .
  3. Use the remote switch to introduce smoke into the EVAP system.
  4. Use the J 41413-VLV to open the EVAP service port. Once smoke is observed, remove the tool.

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

  5. Verify the entire EVAP system with the J 41413-SPT . Smoke should not be observed.
    6. ⇒If smoke is observed, repair the condition as necessary.
  6. Verify the EVAP system using the EVAP service port. Connect the J 41413-200 nitrogen/smoke supply hose to the EVAP service port.

    7. Important: The EVAP vent solenoid valve will not remain closed when in the commanded ON state with positive pressure applied to the EVAP system.

  7. Disconnect the EVAP vent line from the vent solenoid, and seal it, using the correct plug from the J 41413-300 .
  8. Use the remote switch to introduce smoke into the EVAP system.
  9. Verify the entire EVAP system with the J 41413-SPT . Smoke should not be observed.
    10. ⇒If smoke is observed, repair the condition as necessary.
  10. Verify the individual EVAP system components for a leak using the J 41413-300 . The EVAP system components should not leak.
    11. ⇒If a condition is found replace the affected component.

Component Testing
  1. Disconnect the EVAP vent line from the vent solenoid.
  2. Command the EVAP vent solenoid valve ON with a scan tool (closed).
  3. Apply vacuum to the EVAP vent solenoid valve port with a hand held vacuum pump. The vacuum should not decrease
    4. ⇒If the vacuum decreases, replace the EVAP vent solenoid valve.

Repair Instructions
    •  Evaporative Emission Canister Replacement
    •  Evaporative Emission Canister Purge Solenoid Valve Replacement
    •  Evaporative Emission Canister Vent Solenoid Valve Replacement
    •  Evaporative Emission System Hoses/Pipes Replacement
    •  Fuel Tank Pressure Sensor Replacement

Repair Verification With w/Service Bay Test

Verify the EVAP system repair using the EVAP Service Bay Test

Repair Verification w/o Service Bay Test
  1. Turn the nitrogen/smoke valve to nitrogen.

    2. Important: The EVAP vent solenoid valve will not remain closed when commanded ON with positive pressure applied to the EVAP system.

  2. Disconnect the EVAP vent line from the vent solenoid, and seal it, using the correct plug from the J 41413-300 .
  3. Use the remote switch to activate the J 41413-200 .
  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.