P0446
DTC P0446
System Description
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid valve Open and the EVAP canister vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.
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 solenoid valves.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0446 Evaporative Emissions (EVAP) Vent System Performance
Conditions for Running the DTC
* DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0220, P0442, P0443, P0449, P0452, P0453, P0455, and P0502 are not set.
* The ignition voltage is between 10-18 volts.
* The barometric pressure (BARO) is more than 74 kPa.
* The fuel level is between 15-85 percent.
* The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).
* The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
* The start-up ECT and IAT are within 8°C (14.4°F) of each other.
* The purge solenoid valve is enabled.
* DTC P0446 runs once per trip when the above conditions have been met.
Conditions for Setting the DTC
* The fuel tank vacuum is more than 8 inches H2O for 5 seconds during the 13 minute test.
OR
* The fuel tank vacuum is less than -2.5 inches H2O or more than +5 inches H2O for 3 seconds after a cold start ignition ON.
* The fuel tank vacuum is greater than a calibrated amount for a calibrated period of time.
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 canister vent inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill condition.
* An EVAP canister, vent hose, or vent solenoid valve that has restricted flow may cause this DTC to set. Using a purge solenoid command with a scan tool will allow vacuum to be applied to the system instead of pressure. With the engine running, the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, the fuel tank vacuum should not increase to more than 5 inches H2O.
* An EVAP canister filter that is restricted can cause this DTC to set. Refer to Evaporative Emission Canister Filter Replacement and Evaporative Emission System Cleaning.
* Disconnecting one component at a time while the EVAP system is under flow will help to pinpoint a restriction in the system.
* Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
* For intermittent conditions, refer to Intermittent Conditions. Intermittent Conditions
Test
Step 1 - Step 6:
Step 7 - Step 12:
