P0446

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The VCM monitors the performance of the EVAP system by applying a predetermined level of vacuum to the EVAP system and monitors the vacuum decay rate. The VCM sets this DTC if the vacuum decay rate is greater than a predetermined value.

CONDITIONS FOR SETTING THE DTC

The following conditions will set the DTC:

^ No MAP sensor DTCs

^ No TP sensor DTCs

^ No VSS DTCs

^ No HO2S DTCs

^ No ECT DTCs

^ The DTC P0125 not active

^ No IAT sensor DTCs

^ The ECT is greater than 4°C (39°F) but less than 30°C (86°F).

^ The IAT is greater than 4°C (39°F) but less than 30°C (86°F).

^ Start up ECT is not more than 8.25°C or 14.85°F greater than the start up IAT.

^ Start up IAT is not more than 1.5°C or 2.7°F greater than the start up ECT

^ The Baro is greater than 72.5 kPa.

^ Excess vacuum present in the EVAP system.

ACTION TAKEN WHEN THE DTC SETS

^ The VCM illuminates the MIL during the first key cycle in which the DTC sets.

^ The VCM stores the conditions which were present when the DTC sets as a Freeze Frame and Fail Records data.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

Check for the following conditions:

^ A loose, missing, damaged, or improperly installed fuel cap

^ Missing or damaged O-rings at EVAP canister fuel vapor and purge line fittings

^ A cracked or punctured EVAP canister

^ A damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line

^ A poor connection at the VCM: Inspect the harness connectors for the following conditions:

- Backed out terminals

- Improper mating

- Broken locks

- Improperly formed or damaged terminals

- poor terminal to wire connection

^ A damaged harness: Inspect the wiring harness to the EVAP vent solenoid EVAP purge solenoid and the fuel tank pressure sensor for an intermittent open or short circuit

^ A kinked, pinched or plugged vacuum source, EVAP purge, or fuel tank vapor line. Verify that the lines are not restricted

Refer to EVAP System Cleaning before starting repairs.

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

The numbers below refer to the step numbers in the diagnostic table.

2. This step checks the Fuel Tank Pressure sensor at atmospheric pressure.

3. This step verifies that the Fuel Tank Pressure sensor accurately reacts to EVAP system pressure changes.

5. Checks for a blocked EVAP Canister.