GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 XLR 🢒 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

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 a vehicle 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 corresponding pressure changes in the fuel tank vapor space. This change is monitored by the engine control module (ECM) using the fuel tank pressure sensor input. The engine ECM then makes a judgment on the integrity of the system. With a 0.51 mm (0.02 in) leak in the system, the amount of pressure change observed is significantly less than that of a sealed system.

Conditions for Running the DTC

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

    • Before the ECM can report DTC P0442 failed, DTCs P0446, P0455, and P0496 must run and pass.
    • 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
    • To help locate intermittent leaks, use the J 41413-200 to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT .
    • To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .
    • 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

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-SPT High Intensity White Light

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. 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. 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 or the purge tube until the leak is located.

Repair Instructions

Important: 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.