P0446

The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapor from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor.
When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element, and then the normal combustion process consumes the fuel vapor.
The system is required in order to detect the evaporative fuel system leaks as small as 0.040 between the fuel filler cap and the purge solenoid. The system can test the evaporative system integrity by applying a vacuum signal (ported or manifold) to the fuel tank in order to create a small vacuum.

EVAP System Description
The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapor from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor.
When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element, and then the normal combustion process consumes the fuel vapor.
The system is required in order to detect the evaporative fuel system leaks as small as 0.040 between the fuel filler cap and the purge solenoid. The system can test the evaporative system integrity by applying a vacuum signal (ported or manifold) to the fuel tank in order to create a small vacuum. The evaporative system includes the following components:
^ The fuel tank.
^ The EVAP canister vent valve/solenoid.
^ The fuel tank pressure sensor.
^ The fuel pipes and hoses.
^ The fuel fill cap.
^ The EVAP vapor lines.
^ The EVAP purge lines.
^ The EVAP canister.
^ The EVAP purge valve/Solenoid.
A RESTRICTED or BLOCKED EVAP VENT PATH is detected by monitoring fuel tank pressure during normal operation (EVAP canister vent valve open, EVAP purge valve normal). With the EVAP canister vent valve open, vacuum level in the system should be very low unless the vent path is blocked. A blockage can be caused by the following conditions:
^ Faulty EVAP vent valve (stuck closed).
^ Plugged kinked or pinched EVAP vent hose.
^ Shorted EVAP canister vent valve/solenoid driver circuit.
^ Plugged EVAP canister.
If any of the conditions described above are present, DTC P0446 will set.

Conditions for Running the DTC
^ No TP sensor, Output Driver Module (ODM), IAT sensor, or MAP sensors DTCs set.
^ System voltage is between 9 and 16 volts.
^ Start-up IAT between 4°C and 30°C (40°F and 86°F).
^ Start-up engine coolant temperature is less than 8°C (14°F) greater than start-up intake air temperature.
^ Start-up intake air temperature is between 4°C and 30°C (40°F and 86°F).
^ Start-up air temperature less than 2°C (4°F) greater than start-up engine coolant temperature.
^ Fuel tank fuel level is between 15% and 85%.
^ BARO is greater than 75 kPa.

Conditions for Setting the DTC
^ Fuel tank pressure is greater than -10 in. H20.
^ The condition is present for up to 30 seconds.

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 if the battery has been disconnected, the diagnostic must fail during 2 consecutive cold start trips before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the first 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 during the third consecutive trip in which the diagnostic has been run and passed.
^ 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.

Diagnostic Aids
Check for the following conditions:
^ kinked, pinched or plugged vent hose.
^ Reviewing the Fail 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.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
1. The Diagnostic System Check prompts you to the basic checks and to store the freeze frame and failure records data on the Scan Tool if applicable.
2. If an EVAP vent valve or EVAP purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction that caused the additional DTC to set will very likely correct the condition that set this DTC.
3. Checks for a fuel tank pressure sensor stuck high condition. The scan tool should read within 1.0 in. H20 of the specified value.
4. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes. The EVAP station is pressurizing a sensor that normally reads vacuum. The Tech II reads high pressure at 0 Volts and high vacuum at 5 Volts. The Tech II can only read a maximum pressure of 6.0 in. of H20 (0 Volts). However the EVAP Service Station can pressurize the system to much higher pressures. The Scan Tool value should be within 0.5 of the specified value.
5. Checks for a plugged or stuck closed EVAP Vent valve/solenoid. The value should decrease to within 1.0 in. HG of the specified value.