GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 Enclave 🢒 DTC 🢒 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 Emissions (EVAP) System Small Leak Detected

Circuit/System Description

The engine off natural vacuum (EONV) test is the small leak detection diagnostic for the evaporative emission system. This diagnostic tests the Evaporative Emission (EVAP) system for a small leak when the key is turned OFF and the correct conditions are met. Heat from the exhaust system is transferred into the fuel tank while the vehicle is operating. When the vehicle is turned OFF and the EVAP system is sealed a change in the fuel tank vapor temperature occurs which results in a corresponding pressure change in the fuel tank vapor space. This change is monitored by the engine control module (ECM) using the fuel tank pressure sensor input. With a leak in the system, the amount of pressure change will be less than that of a sealed system.

Conditions for Running the DTC

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

    • DTCs P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0443, P0446, P0449, P0452, P0453, P0463, P0503, P1106, P1107, P1111, P1112, P1114, P1115, P1516, P2101, P2108, P2120, P2125, P2129, P2138, P2610 are not set.
    • The diagnostic runs once after a cold start drive cycle.
    • The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
    • The start-up engine coolant temperature (ECT) is less than 30°C (86°F).
    • The start-up IAT and ECT are within 8°C (15°F).
    • The barometric pressure (BARO) is greater than 74 kPa.
    • The ambient air temperature is between 2-32°C (36-90°F).
    • The engine run time minimum is 10 minutes.
    • The vehicle has traveled greater than 5 kilometers (3 miles) this trip.
    • The ECT is greater than 70°C (158°F).
    • The fuel level is between 15-85 percent.
    • The ignition is OFF.
    • A refueling event is not detected.
    • DTC P0442 runs once per drive cycle during the hot soak period after the ignition is turned OFF and may require up to 45 minutes to complete. The ECM will not make more than 2 tests per day.

Conditions for Setting the DTC
    • The ECM detects a pressure change that is less than a calibrated amount.
    • The ECM must complete several EONV tests before the diagnostic can turn the MIL ON or OFF.

Action Taken When the DTC Sets

DTC P0442 is a Type A DTC.

Conditions for Clearing the MIL/DTC

DTC P0442 is a Type A DTC.

Diagnostic Aids
    • To help locate intermittent leaks, use the J 41413-200 (J 41413-100) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with a high intensity white light.
    • To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with a high intensity white light.
    • A condition may exist where a leak in the EVAP system only exists under a vacuum condition. This type of leak may be detected using the scan tool Purge/Seal function to create a vacuum in the system and then observe the FTP parameter for vacuum decay.

Reference Information

Schematic Reference

Evaporative Emissions Hose Routing Diagram

Connector End View Reference

Component Connector End Views

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • CH-48096 EVAP Service Access Port Tool
    • GE-41415-50 Fuel Tank Cap Adapter
    • J 41413-200 (J 41413-100) Evaporative Emission System Tester (EEST)

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.
   • 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 (J 41413-100) operation manual for detailed instructions

  1. Connect the J 41413-200 (J 41413-100) to the vehicle at the 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. Using a scan tool, close the EVAP canister vent valve to seal the EVAP system.
  3. Use the flow meter on the J 41413-200 (J 41413-100), calibrated to 0.51 mm (0.020 in) to determine that there is no leak in the EVAP system.
    4. ⇒If a leak is detected, use the J 41413-200 (J 41413-100) 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 .

Repair Verification
  1. Seal the EVAP system and use the flow meter on the J 41413-200 (J 41413-100), calibrated to 0.51 mm (0.020 in) to determine that there is no leak in the EVAP system.
  2. Clear DTCs.