P0446
DTC P0446
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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.
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.
Conditions for Running the DTC
* DTC P0100, P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P0221, P0222, P0223, P0443, P0449, P0451, P0452, P0453, P0458, P0459, P0496, P0497, P0498, P0499, P0560, P0562, P0563, P0700, P2122, P2123, P2127, P2128 or P2138 is not set.
* The ignition voltage is 10-18 volts.
* The Closed Loop fuel control is enabled.
* The engine run time is greater than 10 minutes or the fuel trim is stable.
* The engine is idling.
* The fuel tank pressure (FTP) is between -18.7 and +9.8 mm Hg (-10.0 and +5.2 in. H2O).
* The ambient air temperature (AAT) is between 2-32°C (35-90°F).
* The ECT and the IAT are within 10°C (18°F) of each other at engine start-up.
* The barometric pressure (BARO) is greater than 68 kPa.
* The fuel level is between 15-86 percent.
* The vehicle speed sensor (VSS) is less than 3 km/h (2 mph).
* The above conditions exist for greater than 5 seconds.
* DTC P0446 will attempt to run up to 10 times or until the test completes successfully once per ignition cycle.
Conditions for Setting the DTC
* The FTP is less than -7.5 mm Hg (-4.0 in. H2O).
* The condition is present for greater than 5 seconds during the test.
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 canister vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill condition.
* An EVAP canister filter that is restricted can cause this DTC to set.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Evaporative Emission Control System Description (Evaporative Emission Control System Description)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Programming and Relearning (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON and fuel cap removed, verify that the FTP sensor parameter is between 1.3-1.7 V.
• If not within the specified range, go to the FTP sensor section in Circuit/System Testing.
2. Install the fuel cap.
3. With the engine running, the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 %, the fuel tank vacuum should not increase to more than -15 mm Hg (-8 in. H2O).
• If the fuel tank vacuum is greater than the specified range, go to the restriction section in Circuit/System Testing.
4. 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
Note: 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 %, the fuel tank vacuum should not increase to more than -15 mm Hg (-8 in. H2O).
If the fuel tank vacuum is greater than the specified value, isolate the restriction in the vent path by disconnecting one component at a time while the EVAP canister purge solenoid valve is commanded to 100 % and the vent valve is open.
FTP Sensor
1. Ignition OFF, disconnect the harness connector at the B150 FTP sensor.
2. Ignition OFF, test for less than 5 ohm between the low reference circuit terminal 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 B150 FTP sensor.
Repair Instructions
* Evaporative Emission Canister Vent Solenoid Valve Replacement (Service and Repair)
* Evaporative Emission Canister Replacement (Service and Repair)
* Evaporative Emission Canister Vent Front Pipe Replacement (Evaporative Emission Canister Vent Front Pipe Replacement)
* Evaporative Emission Canister Vent Rear Pipe Replacement (Evaporative Emission Canister Vent Rear Pipe Replacement)
* Fuel Tank Pressure Sensor Replacement (Service and Repair)
* Evaporative Emission Line Replacement - Chassis to Canister (Evaporative Emission Line Replacement - Chassis to Canister)
Repair Verification
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
With the engine running, the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 %, the fuel tank vacuum should not increase to more than -8 in. H2O.