Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provide an overview of each diagnostic category. |
DTC Descriptor
DTC P0446: Evaporative Emissions (EVAP) Vent System PerformanceCircuit/System Description
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid valve Open and the EVAP canister vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inch H2O in a calibrated time, this DTC sets.
FTP Sensor Signal Voltage | Fuel Tank Pressure |
|---|---|
Low, Approximately 1.5 V or less | Positive Pressure |
High, Approximately 1.5 V or more | Negative Pressure/Vacuum |
Conditions for Running the DTC
| • | DTCs P0030, P0036, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0502, P0562, P0563, P0641, P0651, P1133, P1134 are not set. |
| • | The ignition voltage is between 11-18 volts. |
| • | The barometric pressure (BARO) is more than 74 kPa. |
| • | The fuel level is between 15-85 percent. |
| • | The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F). |
| • | The start-up intake air temperature (IAT) is between 4-30°C (39-86°F). |
| • | The start-up ECT and IAT are within 8°C (14.4°F) of each other. |
| • | The purge solenoid valve is enabled. |
| • | DTC P0446 runs once per trip when the above conditions have been met. |
Conditions for Setting the DTC
| • | The FTP sensor is more than 10 inches H2O vacuum for 2 seconds during the 13 minute test. |
| OR |
| The FTP is less than -2.5 inches H2O or more than +5 inches H2O for 3 seconds after a cold start ignition ON. |
| • | The fuel tank vacuum is greater than a calibrated amount for a calibrated period of time. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
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 problem. |
| • | An EVAP canister, vent hose, or vent solenoid valve that has restricted flow may cause this DTC to set. Using a purge solenoid command with a scan tool will allow vacuum to be applied to the system instead of pressure. With the engine running, the EVAP canister vent solenoid valve open, and the EVAP canister purge solenoid valve commanded to 100 percent, the fuel tank vacuum should not increase to more than 10 inches H2O. |
| • | Disconnecting one component at a time while the EVAP system is under flow will help to pinpoint a restriction in the system. |
| • | Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition. |
| • | For intermittent conditions, refer to Testing for Intermittent Conditions and Poor Connections . |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Special Tools Required
| • | J 41413-200 Evaporative Emissions System Tester (EEST) |
| • | GE-41415-50 Interrupted Thread Fuel Tank Adapter |
Circuit/System Verification
- Ignition ON and fuel cap removed, verify that the FTP sensor parameter is between 1.3-1.7 volts.
- With the engine running, the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, the fuel tank vacuum should not increase to more than 8 inches H2O.
| ⇒ | If not within the specified range, go to the FTP sensor section in Circuit/System Testing. |
| ⇒ | If the fuel tank vacuum is greater than the specified range, go to the restriction section in Circuit/System Testing. |
Circuit/System Testing
Important:
• Refer to the
J 41413-200
operation manual for detailed instructions. • 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 percent, the fuel tank vacuum should not increase to more than 8 inches 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 canister purge solenoid valve is commanded to 100 percent and the vent valve is open. |
FTP Sensor
- Ignition ON and fuel cap removed, verify that the FTP sensor parameter is between 1.3-1.7 volts.
- With the GE-41415-50 , connect the J 41413-200 to the fuel filler neck.
- Start the engine.
- Allow the engine to idle.
- Use the Purge/Seal function to seal the system with a scan tool.
- Command the EVAP canister purge solenoid valve to 20 percent.
- Observe the vacuum/pressure gage on the J 41413-200 and the FTP parameter on the scan tool.
- Verify that the vacuum increases to the abort limit on the scan tool or more than 3.2 volts, and the value is closely similar between the scan tool and the vacuum/pressure gage on the J 41413-200 .
| ⇒ | If the FTP sensor parameter is not within the specified range, test the FTP low reference circuit for an open or high resistance. If the circuit tests normal, replace the FTP sensor. |
| ⇒ | If the values are not similar or the voltage is not within the specified range, replace the FTP sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for powertrain control module (PCM) replacement, setup, and programming |
Repair Verification
Important:
• Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize. • Refer to the
J 41413-200
operation manual for detailed instructions.
With the engine running, the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, the fuel tank vacuum should not increase to more than 8 inches H2O.
