P0446

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 table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent valves.

CONDITIONS FOR RUNNING THE DTC
- DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0452, P0453, P0500 are not set.
- The ignition voltage is between 11-18 volts.
- The barometric pressure (BARO) is more than 81 kPa.
- The fuel level is between 15-85 percent.
- The engine coolant temperature (ECT) is between 5-32°C (41-90°F).
- The intake air temperature (IAT) is between 5-32°C (41-90°F).
- The start-up ECT and IAT are within 9°C (16°F) of each other.
- The engine is running.
- The engine run time is less than 144 seconds.
- No vehicle speed DTCs are set in the transmission control module (TCM).
- The accumulated purge flow is more than 350 grams.

CONDITIONS FOR SETTING THE DTC
The fuel tank vacuum is more than 12 inch H2O for 1.6 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
- 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 canister vent solenoid housing, a temporary blockage at the EVAP canister vent solenoid inlet or a pinched vent hose. A blockage in the EVAP canister vent system may also cause a poor fuel fill condition.
- 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. Diagnostic Strategies

TEST DESCRIPTION

Steps 1 - 7:

Steps 8 - 15:

The number below refers to the step number on the diagnostic table.
2. DTC P0447 may indicate a short to ground in the control circuit of the EVAP canister vent solenoid. This will cause the solenoid to close and DTC P0446 to set.