Description
A restricted or blocked evaporative emission (EVAP) vent path is detected by the control module monitoring the fuel tank pressure (FTP) during normal operation. The control module commands the EVAP vent valve OFF, or open, and the EVAP canister purge valve ON, or open. The FTP should remain low as vacuum is drawn on the EVAP system. If the vent path is blocked or restricted, the vacuum level will increase and DTC P0446 will set.
Conditions for Running the DTC
| • | DTC P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0440, P0442, P0443, P0449, P0452, P0453, P1111, P1112, P1114, P1115, P1120, P1220, or P1221 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) of each other. |
| • | The vehicle speed sensor (VSS) is less than 121 km/h (75 mph). |
Conditions for Setting the DTC
| • | The FTP is less than -10 inches H2O. |
| • | The condition is present for as long as 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. |
Diagnostic Aids
An intermittent condition could be caused by a damaged EVAP vent housing, by a temporary blockage at the EVAP vent valve inlet, or by 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 | 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 | Did DTCs 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 that the Service Bay Test has passed? | -- | Go to Diagnostic Aids | Go to Step 5 | |||||
5 |
Does the scan tool indicate FTP near the specified value? | 0 in H2O | Go to Step 6 | Go to Step 8 | ||||
6 |
Does the scan tool indicate FTP near the second specified value? | 5 in H2O 0 in H2O | Go to Step 10 | Go to Step 7 | ||||
7 | Disconnect the EVAP vapor pipe from the EVAP canister. Does the scan tool indicate FTP near the specified value? | 0 in H2O | Go to Step 13 | Go to Step 11 | ||||
8 | Observe the FTP sensor voltage with a scan tool. 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 FTP 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 FTP 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 |
Does the scan tool indicate that the Service Bay Test has passed? | -- | 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 | |||||
