GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Epica 🢒 DTC 🢒 DTC P0446

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 P0446: Evaporative Emissions (EVAP) Vent System Performance

Circuit/System Description

A restricted or blocked evaporative emission (EVAP) vent path is detected by the control module commanding the purge valve ON (open) and the vent valve ON (closed) allowing a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the purge valve OFF (closed) and the vent valve OFF (open) while monitoring the fuel tank pressure (FTP) sensor for a decrease in vacuum.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves.

Control Module Command

EVAP Canister Purge Valve

EVAP Canister Vent Valve

ON

Open

Closed

OFF

Closed

Open

Conditions for Running the DTC
    • Before the engine control module (ECM) can report DTC P0446 failed, DTCs P0443, P0458, P0459, P0498, and P0499 must run and pass.
    • The ignition 1 voltage is between 9-16 volts.
    •  The engine is running.
    • DTC P0446 runs once an ignition cycle when the above conditions are met.

Conditions for Setting the DTC
    • The fuel tank pressure is greater than -23 mmHg (-12 inches H2O) at cold engine startup.
    •  The above condition is present for at least 5 seconds.

Action Taken When the DTC Sets

DTC P0446 is a Type B DTC.

Conditions for Clearing the DTC

DTC P0446 is a Type B DTC.

Diagnostic Aids

An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent valve inlet or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.

Reference Information

Schematic Reference

    •  Engine Controls Schematics
    •  Evaporative Emissions Hose Routing Diagram

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Description and Operation:

Evaporative Emission Control System Description

Electrical Information Reference

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

DTC Type Reference

Powertrain 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 41413-200 Evaporative Emissions System Tester (EEST)
    • GE-41415-50 Fuel Tank Cap Adapter
    • J 23738-A Hand Vacuum Pump

Circuit/System Verification
  1. Ignition ON, observe the scan tool DTC information parameter. Verify DTC's P0443, P0452, P0453, P0458, P0459, P0498, or P0499 are not set.
    2. ⇒If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Verify the scan tool fuel tank pressure (FTP) sensor voltage parameter is near 0 volts.
  3. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing
  1. Ignition ON, loosen the fuel fill cap. Verify the scan tool FTP sensor voltage parameter is near 0 volts.
    2. ⇒If greater than 4 volts, refer to DTC P0452 or P0453 .

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

  2. Connect the GE-41415-50 to the fuel fill pipe. Connect the J 41413-200 to the GE-41415-50 . Install the fuel tank filler cap to the GE-41415-50 .

    3. Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.

  3. Turn the nitrogen/smoke valve on the J 41413-200 to nitrogen. Use the remote switch and attempt to pressurize the fuel tank with nitrogen to 5 in H20.
    4. ⇒If the FTP sensor parameter indicates a pressure of 8.4 mmHg (4 in H20), test for a blockage or restriction in the EVAP vent line/hoses.
    ⇒If no blockage or restrictions in the EVAP vent line/hoses are found, replace the EVAP vent solenoid.

Component Testing
  1. Remove the EVAP vent solenoid.
  2. Connect the vent solenoid electrical terminals to B+ and ground.
  3. Connect the J 23738-A to a vacuum port on vent solenoid. Apply and hold a vacuum of 10 inches for 30 seconds.
    4. ⇒If the vacuum cannot be obtained and held as specified, replace the EVAP vent solenoid.
  4. Remove the B+ and ground from the vent solenoid, while observing the pressure gage of the vacuum pump.
    5. ⇒If the vacuum does not drop to zero immediately, replace the EVAP vent solenoid.