GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2009 🢒 XLR 🢒 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 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 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, P0128, P0443, P0446, P0449, P0452, P0453, P0463, 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 less than 30°C (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 more 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 more than 8 kilometers (5 miles) this trip.
    • The ECT is more 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 when the above conditions are met.
    • One test occurs at ignition OFF after a drive cycle, and may require up to 45 minutes to complete. No more than 2 tests per day are allowed.

Conditions for Setting the DTC
    • The ECM detects a pressure change that is less than a calibrated amount.
    • Several tests must be completed to report a Fail with up to 17 hours between tests.

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
    • 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 Vent Fitting at the service port to allow the system to fill faster.
    • To help locate intermittent leaks using the J 41413-200 EEST , move all EVAP components while observing smoke with the J 41413-SPT White Light .
    • Individual components can be isolated and tested using adapters in the J 41413-300 Kit .
    • 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

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • CH 48096 EVAP Service Access Port Tool
    • J 41413-200 Evaporative Emission System Tester (EEST)
    • J 41413-300 EVAP Cap and Plug Kit
    • J 41413-SPT High Intensity White Light
    •  41413-VLV EVAP Service Port Vent Fitting

Circuit/System Testing

Note: 

   • 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 EEST operation manual for detailed instructions.

  1. Connect the J 41413-200 EEST 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 Port Tool .
  2. Seal the EVAP system and use the flow meter on the J 41413-200 EEST , 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 EEST to apply smoke to the EVAP system at the service port or the purge tube until the leak is located.

Repair Instructions

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.