GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC W-Series Commercial W4 (W3500/W4500) 🢒 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 provide an overview of each diagnostic category.

DTC Descriptor

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

Circuit 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 control module 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 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 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 control module detects a leak in the EVAP system that is greater than a calibrated amount.
    • Several EONV tests must complete before the diagnostic can report the results.

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
    • To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .
    • 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 J 41413-300 .
    • A condition may exist where a leak in the EVAP system only exists under a vacuum condition. By using the scan tool Purge/Seal function to create a vacuum, seal the system and observe the FTP parameter for vacuum decay. This type of leak may be detected.

Reference Information

Schematic Reference

Evaporative Emissions Hose Routing Diagram

DTC Type Reference

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 41413-200 Evaporative Emissions System Tester (EEST)
    • J 41413-300 EVAP Cap and Plug Kit
    • J 41413-311 EVAP Plug

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

  1. Connect the J 41413-200 to the vehicle at the EVAP service port.
  2. 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.
    3. ⇒If a leak is detected, use the J 41413-200 to apply smoke to the EVAP system at the service port until the leak is located.

Repair Instructions

The malfunction indicator lamp (MIL) may remain ON after the repair unless the DTCs are cleared.