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
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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 that would cause excess amounts of vacuum to be developed in the EVAP system. With the purge valve open and the vent valve open, if the EVAP system vacuum goes above a calibrated threshold, the test will fail.
Typical Scan Tool Data
Conditions for Running the DTC
* DTC P00C8, P00C9, P010C, P010D, P0068, P16F3, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0122, P0123, P0125, P0128, P160E, P160D, P0191, P0192, P0193, P0222, P0223, P0443, P0449, P0452, P0453, P0454, P0502, P0503, P0606, P0722, P0723, P1104, P2100, P2101, P2102, P2103, P2135, P2227, P2228, P2229, or P2230 is not set.
* The ignition voltage is greater than 11 V.
* The engine run time is less than 17 min.
* The start up IAT is between 4-30°C (39-86°F).
* The start up ECT is less than 32°C (90°F)
* The barometric pressure (BARO) is greater than 70 kPa.
* The fuel level is between 10-90 %.
* The above conditions exist for greater than 5 s.
* DTC P0446 will start and run once per cold start.
* This test runs with normal purge, and the vent valve is open.
Conditions for Setting the DTC
* Fuel tank vacuum is greater than 3 kPa (0.43 PSI) for 5 s before purge volume is greater than 6 L (1.6 gal).
* After setting the DTC for the first time, 2 L (0.5 gallons) of fuel must be consumed before setting the DTC for the second time.
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 may also cause a poor fuel fill problem.
Reference Information
Schematic Reference
Engine Controls Schematics ((LFX)) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Evaporative Emission Control System Description Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON and fuel cap removed, verify that the fuel tank pressure (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 vent solenoid valve open, use a scan tool to command the EVAP purge solenoid valve to 100 %. The fuel tank vacuum should not increase to more than -15 mmHg (-8 in.H2O).
• If the fuel tank vacuum is greater than the specified range, go to the restriction section in Circuit/System Testing.
4. Using the scan tool, decrease the canister purge duty cycle from 100 % to 0 %. The vacuum should decrease to near zero.
• If the fuel tank vacuum does not return to zero, or appears to decrease too slowly, go to the restriction section in Circuit/System Testing.
5. 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:
Perform the Circuit/System Verification before proceeding with the Circuit/System Testing.
Restriction
1. With the engine running, the EVAP vent solenoid valve open, and the EVAP purge solenoid valve commanded to 100 %, the fuel tank vacuum should not increase to more than -15 mmHg (-8 in.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 purge solenoid valve is commanded to 100 % and the vent valve is open.
2. Using the scan tool, decrease the canister purge duty cycle from 100 % to 0 %. The vacuum should decrease to near zero.
• If the fuel tank vacuum does not return to zero, or appears to decrease too slowly, inspect and repair the components in the EVAP vent system for a restriction.
Fuel Tank Pressure Sensor
1. Ignition OFF, disconnect the harness connector at the B150 fuel tank pressure sensor.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 min for all vehicle systems to power down. Test for less than 5 ohms 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 fuel tank pressure sensor.
Repair Instructions
Evaporative Emission Canister Vent Solenoid Valve Replacement Service and Repair
Repair Verification
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
With the engine running, the EVAP vent solenoid valve open and the EVAP purge solenoid valve commanded to 100 %, the fuel tank vacuum should not increase to more than -15 mmHg (-8 in.H2O).