Diagnostic Instructions
DTC Descriptor
DTC P0446: Evaporative Emission (EVAP) Vent System Performance
Circuit/System Description
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path that would cause excess amounts of vacuum to be developed in the EVAP system. With the purge valve open and the canister vent valve open, if the EVAP system
vacuum goes above a calibrated threshold, the test will fail.
FTP Sensor Signal Voltage
| Fuel Tank Pressure
|
Low, Approximately 1.5 V or less
| Positive Pressure
|
High, Approximately 1.5 V or more
| Negative Pressure/Vacuum
|
Conditions for Running the DTC
| • | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0128, P0222, P0223, P0443, P0449, P0452, P0453, P0455, P0496, P0502, P0560, P0562, P0563 are not set. |
| • | The ignition voltage is between 11-18 volts. |
| • | The barometric pressure (BARO) is more than 68 kPa. |
| • | The fuel level is between 15-85 percent. |
| • | The estimated ambient air temperature is between 2-32°C (35.6-90°F). |
| • | The start-up ECT and estimated ambient air temperature are within 9°C (16.2°F) of each other. |
| • | The vehicle speed sensor (VSS) is less than 1.7 km/h (2 mph). |
| • | The purge solenoid valve is enabled. |
| • | DTC P0446 will attempt to run up to 10 times until it successfully completes. |
| • | DTC P0446 completes one test per trip when the above conditions have been met. |
Conditions for Setting the DTC
The fuel tank pressure (FTP) sensor is more than 3 inches H2O vacuum for 4 seconds during the 10 minute test.
Action Taken When the DTC Sets
DTC P0446 is a Type B DTC.
Conditions for Clearing the MIL/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 canister vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem. |
| • | An EVAP canister filter that is restricted can cause this DTC to set. |
Reference Information
Schematic Reference
Connector End View Reference
Component Connector End Views
Description and Operation
Evaporative Emission Control System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
| • | J 41413-200
(J 41413-100) Evaporative Emissions System Tester (EEST) |
Circuit/System Verification
- Ignition ON and fuel cap removed, verify that the FTP sensor parameter is between 1.3-1.7 volts.
| ⇒ | If not within the specified range, go to the FTP sensor section in Circuit/System Testing. |
- Install the fuel cap.
- 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 8 inches H2O.
| ⇒ | If the fuel tank vacuum is greater than the specified range, go to the restriction section in Circuit/System Testing. |
Circuit/System Testing
Important: Refer to the
J 41413-200
operation manual for detailed instructions in
Evaporative Emission System Diagnosis.
Important: Perform the Circuit/System Verification before proceeding with the Circuit/System Testing.
Restriction
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 8 inches H2O.
| ⇒ | If the fuel tank vacuum is greater than the specified value, isolate the restriction by disconnecting one component at a time while the EVAP canister purge solenoid valve is commanded to 100 percent and the vent valve is open. |
FTP Sensor
- Ignition OFF, disconnect the harness connector at the FTP sensor.
- Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 and ground.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the FTP sensor. |
Repair Instructions
Repair Verification
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 8 inches H2O.
