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 provides an overview of each diagnostic category. |
DTC Descriptor
DTC P0446: Evaporative Emissions (EVAP) Vent System PerformanceCircuit/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 inch H2O in a calibrated time, this DTC sets.
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 P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0128, P0443, P0449, P0451, P0453, P0454, P1106, P1107, P1111, P1112, P1114, P1115, P1125, P1516, P2101, P2108, P2119, P2120, P2125, P2138 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 less than 30°C (86°F). |
| • | The start-up intake air temperature (IAT) is less than 30°C (86°F). |
| • | The start-up ECT and IAT are within 9°C (16°F) of each other. |
| • | DTC P0446 runs once per trip when the above conditions have been met. |
Conditions for Setting the DTC
| • | The fuel tank pressure (FTP) sensor is more than 8 inches H2O vacuum for 2 seconds during the 13 minute test. |
| OR |
| The FTP 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
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, 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 8 inches H2O. |
| • | An EVAP canister filter that is restricted can cause this DTC to set. Refer to Evaporative Emission Canister Replacement . |
| • | Disconnecting one component at a time while the EVAP system is under flow will help to pinpoint a restriction in the system. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Special Tools Required
| • | J 41413-200 Evaporative Emissions System Tester (EEST) |
| • | GE-41415-50 Fuel Tank Cap Adapter |
Circuit/System 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.
- Engine running, observe the DTC information with a scan tool. DTC P0446 should not set.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Important: Refer to the J 41413-200 operation manual for detailed instructions.
- Inspect the EVAP vent system for a restriction.
- Test the low reference circuit of the FTP sensor for an open or for high resistance.
- With the GE-41415-50 , connect the J 41413-200 to the fuel filler neck.
- Start the engine.
- Allow the engine to idle.
- Use the Purge/Seal function to seal the system with a scan tool.
- Command the EVAP Canister purge solenoid valve to 20 percent.
- Observe the vacuum/pressure gage on the J 41413-200 and the FTP parameter on the scan tool.
- Verify that the vacuum increased to the abort limit on the scan tool or more than 3.2 volts, and the value is closely similar between the scan tool and the vacuum/pressure gage on the J 41413-200 .
| ⇒ | If the values are not similar or the voltage did not reach 3.2 volts, replace the FTP sensor. |
Repair Instructions
| • | Control Module References for engine control module (ECM) replacement, setup, and programming |
Repair Verification
Important:
• Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize. • Refer to the
J 41413-200
operation manual for detailed instructions.
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.
