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
Typical Scan Tool Data
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 and vent valve open, if the EVAP system vacuum goes above a calibrated threshold, the test will fail.
Conditions for Running the DTC
* DTC P00C8, P00C9, P010C, P010D, P012B, P012C, P012D, P16A0, P16A1, P16A2, P160E, P160D, P16F3, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114 P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0191, P0192, P0193, P0222, P0223, P0443, P0449, P0452, P0453, P0454, P0502, P0503, P0601, P0604, P0606, P0722, P0723, P1104, P1221, P1682, P2100, P2101, P2102, P2103, P2135, P2176, is not set.
* The ignition voltage is 11-32 V.
* The barometric pressure (BARO) is greater than 70 kPa.
* The startup engine coolant temperature (ECT) is less than 35°C (95°F).
* The startup intake air temperature (IAT) is between 4-30°C (39-86°F).
* The fuel level is between 10-90 %.
* DTC P0446 runs once per cold start, for up to 17 min, when the above conditions are met.
Conditions for Setting the DTC
* The fuel tank vacuum is greater than 12 in H2O vacuum for 5 s before 6 L (1.3 gal) of purge volume.
OR
* The FTP is less than -2.5 in H2O or more than 5 in for 60 s after a cold start.
* After setting the DTC for the first time, 2 L (0.5 gal) 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 solenoid valve inlet, fresh air filter or air snorkel or a pinched vent hose. A blockage in the vent system may also cause a poor fuel fill problem.
* Ensure that the reference port on the FTP sensor is unobstructed. Inspect for accumulated debris on the sensor. If present, clean with shop air and brush.
* An EVAP canister filter that is restricted could prevent fuel vapor pressure from bleeding off fast enough and 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 A/C Compressor Clutch
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 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. 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
Note: 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 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 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 the components in the EVAP vent system for a restriction as described in diagnostic aids.
Fuel Tank Pressure Sensor
1. Ignition OFF, disconnect the harness connector at the B150 Fuel Tank Pressure Sensor.
2. 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
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Evaporative Emission Canister Vent Solenoid Valve Replacement Service and Repair
* Fuel Tank Pressure Sensor Replacement Service and Repair
* Control Module References Control Module References for ECM replacement, setup, and programming
Repair Verification
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 mm Hg (-8 in H2O).