Diagnostic Trouble Code (DTC) P0444
EVAP Purge Control Circuit No Signal
Features of the Circuit
The evaporative emission (EVAP) system comprises the following components:
Fuel tank.
EVAP vent solenoid.
Fuel pipes and hoses.
Fuel vapor lines.
Fuel cap.
EVAP canister.
Purge lines.
EVAP canister purge valve.
EVAP service port.
Further Details:
The evaporative emission system is probed by applying vacuum to the EVAP system and monitoring for a vacuum decay.
The engine control module (ECM) monitors the vacuum level through the fuel tank pressure sensor signal.
The EVAP canister purge valve and the EVAP vent solenoid are turned on at the nick of time, allowing the engine to suck up a small vacuum on the entire EVAP system.
After the requisite vacuum level has been obtained, the EVAP canister purge valve is switched OFF, locking the system entirely.
If sufficient vacuum level cannot be derived, a large leak is indicated. This can be caused by the following conditions :
Missing or faulty fuel cap.
Disconnected or flawed fuel tank pressure sensor.
Disconnected, damaged, pinched, or blocked EVAP purge line.
Disconnected or erroneous EVAP canister purge valve.
Disconnected or faulty EVAP vent solenoid.
Open ignition feed circuit to the EVAP vent or purge solenoid.
Damaged EVAP canister.
Leaking fuel sensor assembly O-ring.
Leaking fuel tank or fuel filler beck.