P0446

Circuit Description
The PCM monitors the performance of the 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 exceeds a predetermined amount of time.

Conditions for Running the DTC
^ DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0420, P0430, P0500, P0502, P0503, P0562, P0563, P1120, P1220, P1221, and HO2S DTCs are not set.
^ The ignition voltage is between 10 and 18 volts.
^ The barometric pressure is more than 75 kPa.
^ The fuel level is between 15% and 85% of full capacity.
^ The engine coolant temperature is between 4°C (39°F) and 30°C (86°F).
^ The intake air temperature is between 4°C (39°F) and 30°C (86°F).
^ The start up engine coolant temperature and the intake air temperature are within 9°C (16°F) of each other.

Conditions for Setting the DTC
^ The EVAP vacuum decay rate is greater than a predetermined value when the PCM commands the vent solenoid open.
^ The conditions are present for greater than 2.0 seconds.

OR

^ The vacuum present in the EVAP system is greater than a predetermined value when the vent solenoid is command open during normal purge.
^ The conditions are present for greater than 4.0 seconds.

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. Use the scan tool data display parameter of EVAP Test Result to determine if this DTC has failed or passed for this ignition cycle.

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure records.

Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL OFF after three consecutive ignition cycles that the diagnostic runs and does not fail.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.

Diagnostic Aids

Important:
^ Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter kit J 35616-A. Using this kit prevents damage to the harness/component terminals.
^ An accurate indication of fuel level is required for the PCM to properly Pass or Fail this DTC. Always diagnose fuel level sensor DTC's before performing this diagnostic table. Always monitor 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.
^ 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
^ Inspect for charcoal release from the vapor canister.
^ The vacuum and pressure in the EVAP system is measured in inches of H2O (water). Most gauges measure vacuum in inches of Hg (mercury) and pressure in psi (pounds per square inch). The table illustrates how the values compare:

Conditions for Running the Service Bay Test
^ The battery voltage is between 10.5 and 18.0 volts.
^ The fuel level is between 15% and 85% of the full capacity.
^ The engine temperature is between 3.5°C (38°F) and 35°C (95°F).
^ Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed.
^ For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
2. An intermittent leak or restriction is indicated if the vehicle passes the Service Bay Test. If the Service Bay Test can not be run, you must allow the vehicle to set until the conditions are met.
3. An open in the Fuel Tank Pressure sensor ground circuit causes a high Fuel Tank Pressure sensor voltage. An open ground circuit may cause DTC P0446 to set. Refer to DTC P0453 for further diagnosis. P0453
4. This step verifies that the Fuel Tank Pressure sensor responds to a change in vacuum.
5. This step isolates the EVAP system from the Fuel Tank Pressure sensor. A Fuel Tank Pressure sensor that does not correctly respond to pressure (or vacuum) causes this DTC to set. The Fuel Tank Pressure sensor range is from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).
7. This step is testing the vapor canister and the EVAP Vent Valve for a restriction.