P0443

CIRCUIT DESCRIPTION
The Evaporative Emission (EVAP) solenoid valve is Pulse Width Modulated (PWM). The Powertrain Control Module (PCM) controls the EVAP canister purge solenoid valve duty cycle by controlling the amount of purge valve solenoid ON time. The scan tool displays the amount of ON time as a percentage. This value is the amount of available vacuum that is applied to the EVAP system.

An ignition voltage is supplied directly to the EVAP canister purge valve. The PCM controls the solenoid by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. Each driver has a fault line which the PCM monitors. The voltage of the control circuit should be low, near 0 volts, when the PCM commands a component ON. The voltage potential of the circuit should be high, near the battery voltage, when the PCM commands the control circuit to a component OFF. If the fault detection circuit senses a voltage other than what the PCM expects, the fault line status changes causing the DTC to set.

CONDITIONS FOR RUNNING THE DTC
^ The engine speed is more than 400 RPM.
^ The ignition voltage is between 6-18.0 volts.

CONDITIONS FOR SETTING THE DTC
^ The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
^ The conditions are present for a minimum of 5 seconds.

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

IMPORTANT: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

Using the Freeze Frame/Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions such as the RPM, the engine load, the vehicle speed, the temperature etc., that you observed. This will isolate when the DTC failed.

For an intermittent,refer to Symptoms - Computers and Control Systems. Standard Model (Non-Alternative Fuels)

TEST DESCRIPTION

Steps 1-7:

Steps 8-15:

The numbers below refer to the step numbers on the diagnostic table.
2. Tests the ON and OFF states of the solenoid.
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.
13. If no problems are found in the control circuit or the connection at the PCM, the PCM may be faulty, however, this is an extremely unlikely failure.