| Table 1: | DTC P0446 |
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 Open and the EVAP canister vent solenoid 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 Closed and the EVAP canister vent solenoid 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 valves.
Control Module Command | EVAP Canister Purge Solenoid | EVAP Canister Vent Solenoid |
|---|---|---|
ON | Open | Closed |
OFF | Closed | Open |
Conditions for Running the DTC
| • | DTC P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0444, P0445, P0447, P0448, P0449, P0451, P0452, P0453, P0496 are not set. |
| • | The ignition voltage is between 10-18 volts. |
| • | The barometric pressure (BARO) is more than 75 kPa (11 psi). |
| • | The fuel level is between 15-85 percent. |
| • | The engine coolant temperature (ECT) is between 4-65°C (39-149°F). |
| • | The intake air temperature (IAT) is between 4-75°C (39-167°F). |
| • | The start-up ECT and IAT are within 9°C (16°F) of each other. |
| • | The vehicle speed sensor (VSS) is 0 km/h (0 mph). |
Conditions for Setting the DTC
| • | The FTP is less than -10 inches H2O. |
| • | The condition is present for 30 seconds. |
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. |
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Evaporative Emissions Hose Routing Diagram | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||
2 |
Does the scan tool indicate that the Service Bay Test has passed? | -- | Go to Diagnostic Aids | Go to Step 3 | ||||
3 | Inspect the evaporative emission (EVAP) system for the following conditions:
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 4 | ||||
4 |
Is the Fuel Tank Pressure parameter in H20 within the specified value? | -1 and +1 in H20 | Go to Step 5 | Go to Step 9 | ||||
5 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 | ||||
6 |
Does the EVAP vent valve open and close? | -- | Go to Step 8 | Go to Step 7 | ||||
7 | Replace the EVAP vent valve. Refer to Evaporative Emission Canister Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
8 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
9 | Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
10 |
Does the scan tool indicate that the Service Bay Test has passed? | -- | Go to Step 11 | Go to Step 3 | ||||
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
