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 Emission (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. The engine control module (ECM) uses the fuel tank pressure (FTP) sensor to monitor EVAP system vacuum. With the purge and vent valves open, if the EVAP system vacuum goes above a calibrated threshold, P0446 will set.
The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP purge and vent solenoid valves.
Conditions for Running the DTC
* DTCs P0068, P00C8, P00C9, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0121, P0122, P0123, P0128, P0191, P0192, P0193, P0222, P0223, P0443, P0601, P0604, P0606, P16A0, P16A1, P16A2, P16F3, P2101, P2135, P2176 are not set.
* The ignition voltage is between 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 (1.6 gal) of purge volume.
OR
* The FTP is less than -2.5 in. H2O or more than 5 in H20 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 Outside Rearview Mirror - Driver
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
Special Tools
* CH 41415-30 Fuel Tank Cap Adapter
* GE 41413-A Evaporative Emissions System Tester (EEST)
For equivalent regional tools, refer to Special Tools Tools and Equipment
Circuit/System Verification
1. Ignition ON.
2. Verify DTC P0443 is not set.
• If the DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle
• If the DTC is not set
3. Ignition OFF, remove the fuel tank filler cap. Ignition ON.
4. Verify the scan tool Fuel Tank Pressure Sensor parameter is between 1.3-1.7 V.
• If not between the 1.3-1.7 V
Refer to P0452, P0453 within DTC P0451-P0454 P0451
• If between the 1.3-1.7 V
5. Install the fuel tank filler cap. Engine idling at operating temperature for 5 min,
6. Verify the scan tool Fuel Tank Pressure Sensor parameter does not increase to greater than 2.5 V when commanding the EVAP Purge Solenoid Valve to 50 %.
• If greater than 2.5 V
Refer to Circuit/System Testing.
• If 2.5 V or less
7. 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.
• 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.
1. Test for a blockage or restrictions in the EVAP system components listed below and repair as necessary.
* Evaporative Emission Vent System Hoses
* Evaporative Emission Canister
* Q13 Evaporative Emission Vent Solenoid Valve
* Evaporative Emission Vent Filter
2. Reconnect all previously disconnected EVAP hardware.
Note: Refer to the GE-41413-A Evaporative Emissions System Tester (EEST) operation manual for detailed instructions in Evaporative Emission System Diagnosis Evaporative Emission System Diagnosis
3. Remove the fuel fill cap and connect the CH 41415-30 to the fuel tank filler neck. Connect the GE 41413-A to the CH 41415-30.
4. Ignition ON, seal the EVAP system with a scan tool.
5. Turn the nitrogen/smoke valve on the GE 41413-A to nitrogen.
Note: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
6. Use the remote switch to activate the GE 41413-A and pressurize the fuel tank to 5.0 in H20.
7. Verify the scan tool Fuel Tank Pressure Sensor parameter is 0 in H20 when commanding the EVAP Vent Solenoid Valve to OFF.
• If not 0 in H20
Test for a blockage or a restriction in the EVAP vent hose or inlet. If the inlet or hose test normal, replace the Q13 Evaporative Emission Vent Solenoid Valve.
• If 0 in H20
8. 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.
• If the DTC sets
Refer to step 1 above.
• If the DTC does not set
9. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Evaporative Emission Canister Vent Solenoid Valve Replacement Service and Repair
* Evaporative Emission Canister Replacement Service and Repair
* Fuel Tank Pressure Sensor Replacement Service and Repair