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 Performance.Circuit/System 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 H2O in a calibrated time, DTC P0446 will set.
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 valves.
Control Module Command | EVAP Canister Purge Valve | EVAP Canister Vent Valve |
|---|---|---|
ON | Open | Closed |
OFF | Closed | Open |
Conditions for Running the DTC
| • | DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0300, P0402, P0404, P0405, P0406, P0443, P0451, P0452, P0453, P0454, P0461, P0462, P0463, P0464, P0488, P0498, P0499, P0502, P0506, P0507, P2110, P2195, and P2196 are not set. |
| • | One of the following conditions is met: |
| - | The ignition is off for greater than 12 hours. |
| - | OR |
| - | The start-up intake air temperature (IAT) and the start-up engine coolant temperature (ECT) are within 8°C (46°F). |
| • | The ignition 1 voltage is between 11-16 volts. |
| • | The barometric pressure (BARO) is greater than 72 kPa. |
| • | The start-up ECT and start-up IAT are between 4-34°C (39-93°F). |
| • | The start-up IAT is 3°C (37°F) less than the actual IAT. |
| • | The purge enable time is less than pre-determined value based on startup ECT. |
| • | The fuel level is between 6-93 percent. |
| • | The engine run time is between 1-360 seconds plus purge enable time. |
| • | The restricted path test time is completed in less than 220 seconds. |
| • | The DTC run once an ignition cycle when the above conditions are met. |
Conditions for Setting the DTC
| • | Fuel tank pressure is greater than 9.3 mm Hg (8 inch H2O) or less than -4.7 mm Hg (-2.5 inch H2O) at cold engine startup. |
| • | The above condition is present for at least 2 seconds. |
Action Taken When the DTC Sets
DTC P0446 is a Type A DTC.
Conditions for Clearing the DTC
DTC P0446 is a Type A DTC.
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.
Reference Information
Schematic Reference
Connector End View 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 Evaporative Emissions. System Tester (EEST) |
| • | GE-41415-50 Fuel Tank Cap Adapter |
Circuit/System Verification w/Service Bay Test
- Verify the EVAP system using the EVAP Service Bay Test. DTC P0446 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Verification w/o Service Bay Test
- Ignition ON, observe the DTC information with a scan tool. DTC's P0443, P0452, P0453, P0458, P0459, P0498, or P0499 should not set.
- Observe the scan tool fuel tank pressure (FTP) sensor pressure parameter. The reading should be near 0 in H2O.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
| ⇒ | If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
Circuit/System Testing
- Ignition OFF, remove the fuel tank filler cap.
- Ignition ON, observe the scan tool fuel tank pressure sensor voltage parameter. Verify the FTP sensor pressure parameter is less than 4 volts.
- Engine running, seal the EVAP system using the EVAP purge seal function with a scan tool. Command the purge open to 20 percent. Seal the system at -8.00 in H20. Exit the system seal. Verify the FTP sensor pressure parameter decreases to 0 in H2O.
| ⇒ | If greater than the specified range, refer to DTC P0452 or P0453. |
| ⇒ | If the FTP sensor parameter does not decrease, check for a blockage or restrictions in the EVAP vent hose, or replace the EVAP vent solenoid valve. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Repair Verification w/Service Bay Test
Verify the EVAP system repair using the EVAP Service Bay Test
Repair Verification w/o Service Bay Test
- Start the engine.
- Seal the EVAP system using the EVAP purge seal function with a scan tool.
- Command the purge open to 20 percent. Seal the EVAP system at -8.00 in H20. Exit the system seal.
- Verify the scan tool FTP sensor pressure parameter decreases to near 0 in H2O.
