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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Sierra Denali 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 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/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
    • DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0222, P0223, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0462, P0463, P0464, P0496, P0502, P0503, P0608, P0641, P0651, P1516, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138 are not set.
    • The ignition 1 voltage is between 10-16 volts.
    • The barometric pressure (BARO) is greater than 74 kPa.
    • No fuel filling during the EONV test period.
    • The fuel level is between 15-85 percent.
    • The start-up engine coolant temperature (ECT) and the start-up intake air temperature (IAT) are between 0-40°C (32-104°F).
    • The barometric pressure (BARO) is more than 74 kPa.
    • The engine run time before engine shut-off was greater than 10 minutes.
    • The drive distance before engine shut-off was more than 5 kilometers (3.1 miles).
    • The ignition is OFF.
    • The ambient air temperature at the end of the drive cycle is between 0-32°C (32-93°F).
    • 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 controller will not make more than 2 test attempts per day. The time since the last completed EONV test must be at least 17 hours

Conditions for Setting the DTC
    • The ECM detects a leak in the EVAP system that is greater 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 DTC

DTC P0442 is a Type A DTC.

Diagnostic Aids
    • The EVAP system can be filled with smoke more quickly and completely by opening the system opposite the end where the smoke is injected. 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.

Reference Information

Schematic Reference

Evaporative Emissions Hose Routing Diagram

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Description and Operation

Evaporative Emission Control System Description

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • CH-48096 EVAP Service Access Port Tool
    • 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 Tool

Circuit/System Testing

Important: 

   •  Refer to the J 41413-200 operation manual for detailed instructions in Evaporative Emission System Diagnosis.
   • Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize.
   • Ensure that the underbody temperature of the vehicle and the tester are similar.

  1. Connect the J 41413-200 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 , 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 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 , calibrated to 0.51 millimeter (0.020 inch) to determine that there is no leak in the EVAP system.
  2. Clear DTCs.