Diagnostic Instructions
DTC Descriptor
DTC P0446: Evaporative Emissions (EVAP) Vent System Performance
Circuit/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. The vacuum should decrease to near 0 inch H2O in a calibrated time.
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
| • | Before the engine control module (ECM) can report DTC P0446 failed, DTCs P0442 and P0496 must run and pass. |
| • | 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. |
| | 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. |
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) |
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 12 inches H2O.
| ⇒ | If the fuel tank vacuum is greater than the specified range, go to the restriction section in Circuit/System Testing. |
- 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. |
| • | 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 12 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 ON and fuel cap removed, verify that the FTP sensor parameter is between 1.3-1.7 volts.
| ⇒ | If the FTP sensor parameter is not within the specified range, test the FTP low reference circuit for an open or high resistance. If the circuit tests normal, replace the FTP sensor. |
- 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 increases 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 is not within the specified range, 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 12 inches H2O.
