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 inches H2O in a calibrated time, this DTC sets.
The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent solenoid valves.
Control Module Command | EVAP Canister Purge Solenoid | EVAP Canister Vent Solenoid |
|---|---|---|
ON | Open | Closed |
OFF | Closed | Open |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0446 Evaporative Emissions (EVAP) Vent System Performance
Conditions for Running the DTC
| • | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0135, P0452, P0453, P0502, P0503, P0601, P0602, P1133, and P1621 are not set. |
| • | The throttle position is between 7-35 percent. |
| • | 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 vehicle speed sensor (VSS) is less than 137 km/h (85 mph). |
| • | The purge solenoid valve is enabled. |
| • | DTC P0446 runs once per trip for 1 minute and 40 seconds when the above conditions have been met. |
Conditions for Setting the DTC
| • | The fuel tank vacuum is less than 12 inches H2O for 5 seconds. |
| • | There is more fuel tank vacuum than expected at a calibrated 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
| • | The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. 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 will also cause a poor fuel fill condition. |
| • | 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 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 9 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 Intermittent Conditions . |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Evaporative Emissions Hose Routing Diagram and Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 | Inspect the evaporative emission (EVAP) system for the following conditions:
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 3 | ||||||
3 |
Do you hear or feel the EVAP canister vent solenoid valve click when commanded ON and OFF? | -- | Go to Step 4 | Go to Step 11 | ||||||
4 |
Is the Fuel Tank Pressure Sensor parameter within the specified range? | -1 to +1 in H2O | Go to Step 5 | Go to Step 13 | ||||||
5 |
Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results. Important: Refer to the J 41413-200 Evaporative Emissions System Tester (EEST) operation manual for detailed instructions.
Is the Fuel Tank Pressure Sensor parameter more than the second specified value? | 10 in H2O 5 in H2O | Go to Step 6 | Go to Step 13 | ||||||
6 |
Was the Fuel Tank Pressure Sensor parameter within the specified value of the vacuum/pressure gage on the J 41413-200 ? | 1 in H2O | Go to Step 7 | Go to Step 13 | ||||||
7 | Did the Fuel Tank Pressure Sensor parameter on a scan tool display more than the specified value? | 3.2 V | Go to Step 8 | Go to Step 13 | ||||||
8 |
Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results. Important: Refer to the J 41413-200 Evaporative Emissions System Tester (EEST) operation manual for detailed instructions.
Does the Fuel Tank Pressure sensor parameter return to the second specified value? | 5 in H2O -1 to +1 in H2O | Go to Step 9 | Go to Step 16 | ||||||
9 |
With NITROGEN flowing and the EVAP canister vent solenoid valve OPEN, does the Fuel Tank Pressure Sensor parameter remain below the specified value? | 1 in H2O | Go to Step 10 | Go to Step 16 | ||||||
10 |
Does the Fuel Tank Pressure sensor parameter display more vacuum than the specified value? | -4 in H2O | Go to Step 16 | Go to Diagnostic Aids | ||||||
11 |
Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 17 | ||||||
12 | Test the EVAP canister vent solenoid control circuit for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 15 | ||||||
13 | Test for an intermittent and for a poor connection at the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 14 | ||||||
14 | Test the low reference circuit of the FTP sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 | ||||||
15 | Test for an intermittent and for a poor connection at the control module. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 | ||||||
16 | Inspect the EVAP vent system for a restriction. Did you find and correct the condition? | -- | Go to Step 20 | Go to Diagnostic Aids | ||||||
17 | Replace the EVAP canister vent solenoid valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||
18 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||
19 | Replace the powertrain control module (PCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||
20 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 21 | ||||||
21 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
