P0446
CIRCUIT DESCRIPTIONThe evaporative system includes the following components:
^ The fuel tank
^ The EVAP canister vent valve
^ The fuel pipes and hoses The fuel cap
^ The EVAP vapor lines
^ The EVAP purge lines
^ The evaporative emission canister
^ The EVAP purge valve
The PCM tests the EVAP system for the following conditions:
^ Large and small leaks (P0440 and P0442)
^ Excess vacuum (P0446)
^ Purge flow during non-commanded conditions (P1441)
^ Fuel pressure sensor and fuel level sensor faults (P0452, P0453, P0461, P0462, and P0463)
^ EVAP purge and vent valve faults (P1645 and P1646)
The PCM tests for a restriction in the EVAP system by monitoring the level of vacuum during purge. The PCM uses the input from the fuel tank pressure sensor to determine the amount of vacuum in the system. With the vent valve open, and the purge valve at a commanded duty cycle, the PCM should detect a very low amount of vacuum. If the PCM detects a vacuum above the calibrated value, DTC P0446 will set. The following conditions will cause DTC P0446 to set:
^ Malfunctioning EVAP canister vent valve (stuck closed)
^ Plugged, kinked, or pinched EVAP canister vent hose.
^ Plugged EVAP canister
CONDITIONS FOR RUNNING THE DTC
^ No TP sensor, MAP sensor, VSS, IAT sensor, ECT sensor, fuel tank pressure sensor, fuel level sensor, EVAP purge control, or EVAP vent control DTCs are set.
^ Battery voltage is between 10 and 18 volts.
^ Barometric pressure is more than 72 kPa.
^ Fuel level sensor indicates that the fuel level is between 15 and 85 percent, and steady for at least 3.2 seconds. The time limit allows for fuel sloshing in the tank that may cause the fuel level indication to vary outside the fuel level limits.
^ Coolant temperature is between 2°C and 30°C (35.6°F and 86°F).
^ Intake air temperature is between 2°C and 32.7°C (35.6°F and 90.86°F).
^ Start up coolant and intake air temperature are within 14.2°C (57.56°F)of each other.
OR
^ No TP sensor, MAP sensor, VSS, IAT sensor, ECT sensor, fuel tank pressure sensor, fuel level sensor, EVAP purge control, or EVAP vent control DTCs are set.
^ The diagnostic test for DTC P0442 has passed.
^ The PCM is commanding normal purge operation (vent valve open, purge valve at the PCM set duty cycle).
CONDITIONS FOR SETTING THE DTC
The PCM detects an EVAP system vacuum more than -12 inches H20.
ACTION TAKEN WHEN THE DTC SETS
IMPORTANT: Although these diagnostics are considered type A, they act like type B diagnostics under certain conditions. Whenever the EVAP diagnostics report that the system has passed, or the code has been cleared, the diagnostic must fail during two consecutive trips before setting a DTC. The initial failure is not reported to the diagnostic manager or displayed on the scan tool.
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) after the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.
CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn the MIL OFF after the third consecutive trip in which the diagnostic runs and passes.
^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using the scan tool Clear DTC Information function.
DIAGNOSTIC AIDS
IMPORTANT: An accurate indication of fuel level is required for the PCM to properly RUN this diagnostic. Always diagnose fuel level sensor DTC's before performing this diagnostic table. Always check for fuel level sensor DTC's stored as History.
Perform a physical inspection of the EVAP system. Check for the following conditions:
^ A stuck closed EVAP vent valve
^ Plugged, kinked, or pinched EVAP canister vent hose
^ A malfunctioning or damaged vapor canister
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may assist in diagnosing the condition The information may help determine how often the condition that set the DTC occurs.
TEST DESCRIPTION
Steps 1 - 7:
Steps 8 - 13:
