P0446

DTC P0446

Circuit 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. If the vacuum does not decrease to near 0 inches H20 in a calibrated time, DTC P0446 will set.


DTC Descriptors

This diagnostic procedure supports the following DTC. DTC P0446 Evaporative Emissions (EVAP) Vent System Performance


Conditions for Running the DTC

DTCsPO1O1, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P01 17, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0171, P0172, P0174, P0175, P0452, P0453, P0502, P0503, P0641 P0651, P1111, P1112, P1114, P1115, P1121, P1122, P1133, P1134, P1153, and P1154 are not set.

- The system voltage is between 10-18 volts.

- The startup ECT is between 4-30°C (39-86°F). The startup IAT is between 4-30°C (39-86°F).

- The start up ECT and IAT are within 8°C (14°F) of each other.

- The fuel tank level is between 15-85 percent.

- The startup barometric pressure (BARO) is more than 75 kPa.

- The vehicle speed sensor (VSS) is less than 90 km/h (75 mph).

- DTC P0446 runs once per ignition cycle when the above conditions are met.

Conditions for Setting the DTC

Condition 1

- Fuel tank pressure is more than 16.8 mm Hg (9 inch H20) when the vent solenoid is OPEN during normal EVAP purging.

- The above condition is present for at least 23 seconds.

Condition 2

- Fuel tank pressure is more than 9.3 mm Hg (5 inch H20) or less than -4.7 mm Hg (-2.5 inch H20) at cold engine startup.

- The above condition is present for at least 3 seconds.


Action Taken When the DTC Sets

- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.


Conditions for Clearing the MIL/DTC

- The control module turns OFF the malfunction indicator lamp (MIL L) 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

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.


Test Description

DTC P0446 Steps 1-7:

DTC P0446 Steps 8-16:

The number below refers to the step number on the diagnostic table.

4. This test determines if the failure is present or intermittent.