P0446
Schematic:
CIRCUIT DESCRIPTION
The PCM monitors the performance of the EVAP system by applying a predetermined level of vacuum to the EVAP system and then monitors the vacuum decay rate. The PCM sets this DTC if the vacuum decay rate is greater than a predetermined value.
CONDITIONS FOR RUNNING THE DTC
^ DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0420, P0430, P0452, P0453, P0500, P0502, P0503, P0562, P0563, or HO2S DTCs are not set.
^ The ignition voltage is between 10 and 17 volts.
^ The barometric pressure is more than 75 kPa.
^ The fuel level is between 15 percent and 85 percent 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 more than a predetermined value when the vent solenoid is commanded open.
^ The conditions are present for more than 2 seconds.
OR
^ The vacuum present in the EVAP system is more than a predetermined value when the vent solenoid is commanded open during normal purge.
^ The conditions are present for more than 4 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.
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 the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns the Malfunction Indicator Lamp (MIL) OFF after 3 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 40 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 connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/ replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.
^ For any test that requires probing the PCM or a component harness connector, use the J 35616-A connector test adapter kit. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Diagrams.
A fuel tank pressure sensor ground circuit that is open will cause this DTC to set. The Fuel Tank Pressure sensor and the Fuel Level sensor share the same ground. IF DTC P0463 is also set, inspect the common ground for an open.
An accurate indication of fuel level is required for the PCM to properly Pass or Fail this DTC. Always diagnose the fuel level sensor DTCs before performing this DTC diagnostic table. Always inspect for fuel level sensor DTCs stored as History.
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 stuck closed EVAP Vent Valve
^ A restricted or blocked EVAP system hose
^ A restricted or stuck closed fuel tank rollover valves
^ A malfunctioning or damaged vapor canister.
Inspect for charcoal release from the vapor canister. Refer to the EVAP System Cleaning procedure.
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 shows how the values compare.
^ 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.
CONDITIONS FOR RUNNING THE SERVICE BAY TEST
- The battery voltage is between 10.5 and 17.5 volts.
- The fuel level is between 15 percent and 85 percent of the full capacity.
- The engine temperature is between 3.5°C (38°F) and 35°C (95°F).
^ The scan tool displays Test Aborted if any of the above conditions are not met.
^ 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
Steps 1 - 7:
Steps 8 - 14:
The numbers below refer to the step numbers on the Diagnostic Table.
3. 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 can not be run, proceed to step 5. If a fault is not currently present the diagnostic table steps will return you to step 3.
5. Testing 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. An open Fuel Tank Pressure sensor ground circuit will cause this DTC to set. If the Fuel Tank Pressure sensor does not respond to pressure (or vacuum) inspect the ground circuit for an open.
The Fuel Tank Pressure sensor range is from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).
In order to test the Fuel Tank Pressure sensor for vacuum response, command the EVAP Purge Solenoid Valve ON with the engine running and quickly SEAL the system. Leaving the EVAP Purge Solenoid Valve ON for a longer period of time allows a greater level of vacuum to develop.