GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Cobalt 🢒 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/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 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. This turbocharged engine is equipped with a one-way flow check valve that prevents boost pressure from entering the purge line and EVAP system.

Conditions for Running the DTC

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

    • DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0128, P0446, P0452, P0453, P0455, P0496, P0502, P0562, P0563, P0601, P0602, P0606, P2610 are not set.
    • The diagnostic runs once after a cold start drive cycle.
    • The start-up intake air temperature (IAT) is between 2-32°C (36-90°F).
    • The start-up engine coolant temperature (ECT) is colder than 42°C (108°F).
    • The start-up IAT and ECT are within 9°C (16°F).
    • The barometric pressure (BARO) is more than 68 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 km (5 mi) this trip.
    • The shut-down ECT is warmer than 74°C (165°F).
    • The fuel level is between 12-88 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 control module 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 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light.
    • 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.
    • If a small leak is difficult to find, it may be necessary to remove the EVAP components and test them one at a time, using the adapters in the J 41413-300 .
    • The turbocharged engine is equipped with a one-way flow check valve that will prevent boost pressure from entering the purge line and the EVAP system. This check valve will also prevent flow from the J 41413-200 from the purge valve into the EVAP system.

Reference Information

Schematic Reference

Evaporative Emissions Hose Routing Diagram

Description and Operation

Evaporative Emission Control System Description

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Special Tools

    • GE-41415-50 Fuel Tank Cap Adapter
    • J 41413-SPT High Intensity White Light
    • J 41413-VLV EVAP Port Vent Fitting Tool
    • J 41413-200 Evaporative Emission 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 J 41413-200 operation manual for detailed instructions in Evaporative Emission System Diagnosis.

  1. Connect the J 41413-200 nitrogen/smoke hose to the J 41413-311 brass cone adapter. Disconnect the hose at the fuel cap end of the GE-41415-50 . Connect the J 41413-311 to the disconnected hose on the GE-41415-50 . Install the GE-41415-50 filler neck end only to the vehicle.
  2. Seal the system and 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.
    3. ⇒If a leak is detected, use the J 41413-200 to apply smoke to the EVAP system at the filler neck until the leak is located.

Repair Instructions

Clear the DTCs with a scan tool.

Repair Verification
  1. Seal the system and use the flow meter on the J 41413-200 calibrated to 0.51 mm (0.020 in) to determine that there are no leaks in the EVAP system.
  2. Perform the Diagnostic Repair Verification after completing the diagnostic procedure.