P0446
Diagnostic Chart (Part 1 Of 3):
Diagnostic Chart (Part 2 Of 3):
Diagnostic Chart (Part 3 Of 3):
Schematic:
CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) monitors the performance of the Evaporative Emission (EVAP) system by applying a predetermined level of vacuum to the EVAP system then monitors the vacuum decay rate. The PCM sets this DTC if the vacuum decay rate is more than a predetermined value.
CONDITIONS FOR RUNNING THE DTC
^ No active Manifold Absolute Pressure (MAP) DTCs
^ No active Intake Air Temperature (IAT) DTCs
^ No active Throttle Position (TP) DTCs
^ No active Heated Oxygen Sensor (HO2S) DTCs
^ No active Vehicle Speed Sensor (VSS) DTCs
^ No active system voltage DTCs
^ The ignition voltage is between 10-18 volts.
^ The barometric pressure is more than 75 kpa.
^ The fuel level is between 15-85 percent of full capacity.
^ The Engine Coolant Temperature (ECT) is between 4°C (39°F) and 30°C (86°F).
^ The Intake Air Temperature (IAT) is between 4°C (39°F) and 30°C (86°F).
^ The start up ECT and the IAT are within 9°C (16°F) of each other.
CONDITIONS FOR SETTING THE DTC
IMPORTANT: This DTC does not report a first failed test. A first fail of this DTC will have a scan tool status as Not Run.
^ The EVAP vacuum decay rate is more than a predetermined value.
^ The conditions are present for more than 2 seconds.
OR
^ The vacuum present in the EVAP system is more than a predetermined value.
^ The conditions are present for more than 4 seconds.
ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.
DIAGNOSTIC AIDS
IMPORTANT:
^ Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
^ An accurate indication of fuel level is required for the PCM to properly pass or fail this DTC. Always diagnose fuel level sensor DTCs before performing this DTCs diagnostic table. Always inspect for fuel level sensor DTCs stored as History.
^ The Service Bay Test may have to be performed in cold ambient air temperatures when the vehicle is running a winter grade fuel. The scan tool displays a message when the Service Bay Test does not run.
^ Inspect for charcoal release from the vapor canister. Refer to the Evaporative Emission (EVAP) System Cleaning procedure.
CONDITIONS FOR RUNNING THE SERVICE BAY TEST
^ The battery voltage is between 10.5-17.5 volts.
^ The fuel level is between 15-85 percent of the full capacity.
^ The engine temperature is between 3.5°C (38°F) and 35°C (95°F).
Perform a physical inspection of the EVAP system.
Inspect for the following conditions:
^ A loose, missing, defective, or incorrect fuel tank cap
^ Incorrectly routed or defective EVAP system vacuum and vapor lines
^ A malfunctioning or damaged vapor canister
^ Charcoal release from the vapor canister-Refer to Evaporative Emission (EVAP) System Cleaning.
The vacuum and pressure in the EVAP system is measured in inches of Water (H2O). Most gauges measure vacuum in inches of Mercury (Hg) and pressure in pounds Per Square Inch (psi). The following shows how the values compare:
TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. Tests the fuel tank pressure.
4. An intermittent leak or restriction is indicated if the vehicle passes the Service Bay Test. A fuel tank cap that is loose or off causes this DTC to set.
If the Service Bay Test cannot be run, proceed to step 5. If a fault is not currently present, the diagnostic table steps will return you to Step 3.
5. Tests the vapor canister and the EVAP vent valve for restriction.
9. A fuel tank pressure sensor that does not correctly respond to pressure, or vacuum, causes this DTC to set.