P0446

The Evaporative Emission (EVAP) vent valve is supplied switched battery power via the engine controls power relay. The Engine Control Module (ECM) controls the valve by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this Diagnostic Trouble Code (DTC) will set.

CONDITIONS FOR RUNNING THE DTC
^ The ignition voltage is 7.5-15.0 volts.
^ The engine speed is more than 40 RPM.

CONDITIONS FOR SETTING THE DTC
A short to ground, an open circuit, or a short to battery voltage is detected on the control circuit.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ 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
^ Use the J 35616-A Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
^ If an intermittent circuit problem is suspected, check for a damaged harness. Inspect the wiring harness thoroughly. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help locate the fault. Refer to Testing for Intermittent and Poor Connections in Diagrams.

Refer to Intermittent Conditions for the intermittents. Intermittent Conditions

TEST DESCRIPTION

Steps 1-11:

Steps 12-20:

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the valve operates. Repeat the commands as necessary.
3. This check can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm the coil may open, the amps drop to 0, or short, go to above 0.75 amp.
18. If no trouble is found in the control circuit or the connection at the ECM, the ECM may be damaged, however, this is an extremely unlikely failure.