Technical Description of OBD-II Trouble Code
The circuit for the purge control valve in the Evaporative Emission Control System is open.
This diagnostic trouble code (DTC) is a generic OBD-II powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may vary depending on the model.
What does that mean?
In vehicles equipped with Evaporative emission control systems (EVAP), the engine draws in excessive fuel vapors from the gas tank that would otherwise be vented into the atmosphere.
The fuel vapor is routed through a vacuum line to the engine’s intake, and the purge valve/solenoid controls the amount of fuel vapors, as directed by the vehicles powertrain control module (PCM) or engine control module (ECM). The PCM/ECM monitors the voltage to the purge control valve and has detected no change in voltage when the purge valve is commanded on.
Note: This code is similar to codes P0443 and P0445.
Symptoms
Symptoms of a P0444 trouble code may include:
Potential Causes
Possible causes of this DTC may include:
Diagnostic Steps for P0444 DTC
Engine wiring harness – Check all connectors to ensure they are properly plugged in, and look for any loose or damaged wires. Typically, the purge control valve is powered by the battery and controlled by the PCM/ECM through a duty cycle. Using the manufacturer’s wiring diagrams, identify the type of circuit being used and check for the presence of battery voltage at the power side of the control solenoid connector using a digital volt ohm meter (DVOM) set to the volts scale. If there is no battery voltage, trace the wiring back to determine the cause of the voltage loss.
Test the continuity of the control side of the wire harness after disconnecting the plug from the control valve solenoid and the PCM wiring harness. Identify the correct wire at the PCM and control valve harness and check for continuity using the ohms scale on the DVOM. If excessive resistance is found, repair the circuit. If there is no continuity on the circuit, check all connections for damaged wiring, loose pins, or disconnected harnesses, and repair the circuit.
Purge control solenoid – After removing the harness plug, check for continuity at the purge control solenoid connector pins using the DVOM set to the ohms scale. Verify that the resistance is within the manufacturer’s specifications. If there is no continuity, suspect that the solenoid is internally open and replace it with a known good unit.
PCM/ECM malfunction – Since the EVAP system is only activated during certain driving conditions, it will be necessary to monitor the EVAP control operation using an advanced scan tool and perform a road test under the required driving conditions to activate the EVAP system. Some advanced scan tools have an internal test to manually activate the EVAP system. Verify that the PCM/ECM is commanding the EVAP system on. If the system is functioning correctly, it will be necessary to back probe the PCM/ECM wiring harness connector using a graphing multimeter or oscilloscope with a duty cycle feature. Connect the positive lead to the purge control valve pin and the negative lead to a known good ground. The duty cycle should match what is commanded by the PCM/ECM during EVAP operation. If there is no duty cycle present, the PCM/ECM may be at fault.
Other EVAP DTCs: P0440 – P0441 – P0442 – P0443 – P0445 – P0446 – P0447 – P0448 – P0449 – P0452 – P0453 – P0455 – P0456
