GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 LaCrosse 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0442

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 Descriptor

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

Circuit Description

This diagnostic tests the evaporative emission (EVAP) system for a small leak. The diagnostic runs when the ignition is in the OFF position, and the correct conditions are met. While the engine is operating, there are sources of heat transferred into the fuel tank from the following:

    • Exhaust heat
    • Engine heat
    • Ambient temperature

When the engine is stopped and the ignition is in the OFF position, a change in the fuel tank vapor temperature occurs. This results in a change in the pressure of the fuel tank vapor space. This change in pressure is monitored by the control module, using the fuel tank pressure (FTP) sensor input. The EVAP diagnostic detects leaks as small as 0.51 mm (0.02 in).

FTP Sensor Signal Voltage

Fuel Tank Pressure

High, Approximately 1.5 Volts or greater

Negative Pressure/Vacuum

Low, Approximately 1.5 Volts or Less

Positive Pressure

Conditions for Running the DTC

Important: The following conditions must be met prior to the ignition OFF test.

    • DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0125, P0128, P0443, P0446, P0449, P0451, P0452, P0453, P0458, P0459, P0496, P0498, P0499, P0560, P0562, P0563, P0700, P2228, and P2229 are not set.
    • The ignition 1 voltage is greater than 11 volts.
    • A refueling event is not detected
    • The fuel volatility is not excessive.
    • The ambient air temperature (AAT) is between 2-32°C (35-90°F).
    • The start-up intake air temperature (IAT) is between 2-32°C (36-90°F).
    • The start-up engine coolant temperature (ECT) is less than 40°C (104°F) and within 10°C (18°F) of the IAT.
    • The ECT is greater than 74°C (165°F) at engine OFF.
    • The barometric pressure (BARO) is greater than 68 kPa.
    • The fuel level is between 12-88 percent.
    • The vehicle traveled greater than 8 km (5 mi) with vehicle speed above 2.5 km/h (1.6 mph).
    • The engine run time is greater than 10 minutes.
    • DTC P0442 runs once per engine off cycle when the above conditions have been met prior to engine shut down.

Conditions for Setting the DTC

The control module detects approximately 6 vacuum/pressure changes significantly less than a calibrated amount.

Action Taken When the DTC Sets

DTC P0442 is a Type A/B DTC.

Conditions for Clearing the DTC

DTC P0442 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 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

Connector End View Reference

Component Connector End Views

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
    •  CH-48096 EVAP Service Port Access Tool
    • GE-41415-50 Fuel Tank Cap Adapter

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. Command the EVAP vent solenoid closed with a scan tool.

    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 below the red flag.
    6. ⇒If the floating indicator is above the red flag, test for a leak in the EVAP system.
  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 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.

  1. Turn the nitrogen/smoke valve on the control panel to SMOKE.
  2. Command the EVAP vent solenoid closed with a scan tool.
  3. Use the remote switch to introduce smoke into the EVAP system.
  4. Use the J 41413-VLV to open the EVAP service port, if equipped. Or, disconnect the EVAP purge pipe from the purge solenoid. Once smoke is observed, remove the tool, or reconnect the EVAP purge pipe.

    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. Connect the CH-48096 EVAP Service Port Access Tool between the EVAP purge solenoid and the EVAP purge pipe, if necessary.
  7. Command the EVAP vent solenoid closed with a scan tool.
  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.

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

Repair Verification
  1. Turn the nitrogen/smoke valve to nitrogen.
  2. Command the EVAP vent valve closed with a scan tool.
  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.