| 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
| • | DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0449, P0452, P0453, P1106, P1107, P1111, P1112, P1114, P1115, P1121, or P1122 are not set. |
| • | The ignition voltage is between 10-18 volts. |
| • | The barometric pressure (BARO) is more than 75 kPa. |
| • | The fuel level is between 15-85 percent. |
| • | The engine coolant temperature (ECT) is between 4-30°C (39- 86°F). |
| • | The intake air temperature (IAT) is between 4-30°C (39-86°F). |
| • | The start-up ECT and IAT are within 9°C (16°F). |
| • | The vehicle speed sensor (VSS) is less than 121 km/h (75 mph). |
Conditions for Setting the DTC
| • | The FTP is less than -10 in H2O. |
| • | The condition is present for 30 seconds. |
Action Taken When the DTC Sets
| • | The control module will illuminate the malfunction indicator lamp (MIL) when the diagnostic test runs and fails. |
| • | The control module will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The control module will turn the MIL OFF during the first trip in which the diagnostic has been run and passed. |
| • | A last test failed (current DTC) clears when the control module turns OFF the MIL. |
| • | The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Evaporative Emissions Hose Routing Diagram | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||
2 | Did DTC P0443, P0449, P0452 or P0453 set? | -- | Go to Step 3 | |||||
3 | Inspect the EVAP system for the following conditions:
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 4 | ||||
Does the scan tool indicate fuel tank pressure near the specified value? | 0 in H2O | Go to Step 5 | Go to Step 8 | |||||
5 |
Important: Always zero the EVAP pressure and vacuum gages on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
Does the scan tool indicate fuel tank pressure near the second specified value? | 5 in H2O 0 in H2O | Go to Intermittent Conditions | Go to Step 7 | ||||
6 | Disconnect the EVAP vent hose from the EVAP canister vent valve. Does the scan tool indicate fuel tank pressure near the specified value? | 0 in H2O | Go to Step 10 | Go to Step 7 | ||||
7 | Disconnect the EVAP vent hose from the EVAP canister. Does the scan tool indicate fuel tank pressure near the specified value? | 0 in H2O | Go to Step 13 | Go to Step 11 | ||||
8 | With a scan tool, observe the fuel tank pressure sensor voltage. Is the FTP sensor voltage more than the specified value? | 4.3 V | Go to DTC P0453 | Go to Step 9 | ||||
9 | Test for poor connections at the harness connector of the fuel tank pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 | ||||
10 | Replace the EVAP vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
11 | Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
12 | Replace the fuel tank pressure sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
13 | Repair for a blockage in the EVAP vent hose. Did you complete the repair? | -- | Go to Step 14 | -- | ||||
14 |
| 5 in H2O | Go to Step 15 | Go to Step 3 | ||||
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
