Diagnostic Instructions
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, P0114, P0116, P0117, P0118, P0122, P0123, P0222, P0223, P0443, P0449, P0451, P0452, P0453, P0454, P0502, and P2135 are not set. |
| • | The ignition voltage is between 11-18 volts. |
| • | The barometric pressure (BARO) is greater than 70 kPa. |
| • | The start-up ECT is less than 35°C (95°F). |
| • | The start-up IAT is between 4-30°C (40-86°F). |
| • | The purge enable time is less than pre-determined value based on startup ECT. |
| • | The fuel level is between 10-90 percent. |
| • | The engine run time is between 1-360 seconds plus purge enable time. |
| • | The DTC run once an ignition cycle when the above conditions are met. |
Conditions for Setting the DTC
| • | The fuel tank pressure is greater than 8 inches H2O at cold engine startup. |
| • | The above condition is present for at least 5 seconds. |
Action Taken When the DTC Sets
DTC P0446 is a Type B DTC.
Conditions for Clearing the 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 vent valve inlet or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill condition and a stalling condition.
Reference Information
Schematic Reference
Evaporative Emissions Hose Routing Diagram
Description and Operation
Evaporative Emission Control System Description
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0443, P0449, P0452, or P0453 are not set.
- Ignition OFF, remove the fuel tank filler cap.
- Ignition ON, observe the scan tool fuel tank pressure sensor voltage parameter. The FTP sensor voltage parameter should be within 1.3-1.7 V.
- Install the fuel tank filler cap.
- Engine idling at operating temperature for 5 minutes, command the EVAP canister purge solenoid valve to 50 percent. The FTP sensor voltage parameter should not increase to greater than 2.5 volts.
| ⇒ | If greater than the specified value, inspect for a blockage or restrictions in the EVAP system components listed below and repair as necessary: |
- 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.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
