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
* DTCs P00C8, P00C9, P010C, P010D, P16A0, P16A1, P16A2, P160E, P160D, P16F3, P0068, P0101, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0122, P0123, P0125, P0128, P0191, P0192, P0193, P0222, P0223, P0443, P0449, P0452, P0453, P0454, P0502, P0503, P0601, P0604, P0606, P0722, P0723, P1104, P1682, P2100, P2101, P2102, P2103, P2176, P2227, P2228, P2229, P2300 are not set.
* The ignition voltage is between 11-32 V.
* The barometric pressure (BARO) is more than 70 kPa.
* The fuel level is between 10-90 %.
* 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).
* 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 10 L (2.6 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 MIL/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, or a pinched vent hose. A blockage in the vent system may 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 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,
2. Verify the scan tool fuel tank pressure (FTP) sensor parameter is between 1.3-1.7 V.
• If not within the specified range
Refer to Circuit/System Testing
• If within the specified range
Refer to step 6 below
3. Install the fuel cap.
4. Engine running, the EVAP vent solenoid valve open, command the EVAP purge solenoid valve to 100 % with a scan tool. The reading should not increase to greater than -15 mm Hg (-8 in H2O).
• If greater than the specified range
Refer to the restriction section in Circuit/System Testing
• If within the specified range
Refer to step 6 below
5. 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
Refer to the restriction section in Circuit/System Testing.
• If within the specified range
6. 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.
7. Verify the DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing.
• If the DTC does not set
8. All OK.
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 EVAP purge solenoid valve commanded to 100 %, the fuel tank vacuum should not increase to greater than -15 mm Hg (-8 in H2O).
• If greater than the specified range
1. Isolate the restriction by disconnecting one component at a time
• Locate and repair restriction
• If within the specified range
2. Using the scan tool decrease the canister purge duty cycle from 100 % to 0 %. The vacuum should decrease to near zero.
• If the vacuum did not decrease to near zero.
1. Inspect the components in the EVAP vent system for a restriction
• Locate and repair restriction
• If the vacuum decreased to near zero.
3. All OK
Fuel Tank Pressure Sensor
1. Ignition OFF, all vehicle systems OFF, this may take up to 2 min for all vehicle systems to power down.
2. Test for less than 5 ohms between the low reference circuit terminal and ground.
• If 5 ohms or greater
1. Ignition OFF, disconnect the harness connector at the B150 Fuel Tank Pressure Sensor.
2. Test for less than 5 ohms in the low reference circuit end to end.
• If 5 ohms or greater, repair the open/high resistance in the circuit.
• If less than 5 ohms, replace the B150 Fuel Tank Pressure Sensor
• If less than 5 ohms
3. 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).
If greater than the specified range
Refer to Circuit/System Testing.
If within the specified range
All OK