P0446

DESCRIPTION
A restricted or blocked Evaporative Emissions (EVAP) vent path is detected by the PCM monitoring the fuel tank pressure during normal operation. The Powertrain Control Module (PCM) commands the EVAP vent valve OFF (open) and the EVAP canister purge valve ON (open). The fuel tank pressure should remain low as vacuum is drawn on the EVAP system. If the vent path is blocked or restricted, the vacuum level will increase and DTC P0446 will set.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0107, P0108, P0110, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0449, P0452, P0453, P1106, P1107, P1111, P1112, P1114, P1115, P1121, or P1122 are not set.
^ The system voltage is between 10-18 volts.
^ The startup Engine Coolant Temperature (ECT) is between 4-30°C (39-86°F), but the startup ECT is not more than 8°C (14°F) more than the startup Intake Air Temperature (IAT).
^ The startup IAT is between 4-30°C (39-86°F), but the startup IAT is not more than 3°C (7°F) more than the startup ECT.
^ Then fuel tank level is between 30-85 percent.
^ The Barometric Pressure (BARO) is more than 75 kPa.
^ The Vehicle Speed Sensor (VSS) is less than 129 km/h (80 mph).

CONDITIONS FOR SETTING THE DTC
^ The fuel tank pressure is less than -10 inches H2O.
^ The condition is present for as long as 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. 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 fuel fill quality problem. Refer to Poor Fuel Fill Quality To repair a blockage in the EVAP system, refer to Evaporative Emission (EVAP) System Cleaning. Service and Repair

TEST DESCRIPTION

Steps 1-10:

Steps 11-14:

The numbers below refer to the step numbers on the diagnostic table.
4. This test determines if the failure is present or intermittent.
6. This test determines if a small purge vacuum is maintaining a high level of vacuum.