Evaporative Emission Control System Leak Detected

CODE NUMBER
P0442 Evaporative Emission Control System Leak Detected

BACKGROUND
The engine control module turns the evaporative emission ventilation solenoid on in order to shut off the outside air port of the evaporative emission canister. Next, the evaporative emission purge solenoid is driven at the specified duty (approximately 25%) to generate a negative pressure in the fuel tank and purge line, etc. When a negative pressure is generated in the fuel tank and purge line etc., the evaporative emission purge solenoid turns off and the fuel tank and purge line, etc. are sealed. After they are sealed, monitoring of pressure differences inside the fuel tank starts, and if there is large drop in pressure over a given time (if the negative pressure is leaking out into the atmosphere and the pressure has approached barometer pressure), the engine control module judges that there is a leak in the fuel tank, purge line or vapor line. Furthermore, if the fuel tank internal pressure does not drop even if the evaporative emission purge solenoid is driven while the outside air port of the canister is shut off (because of a blockage in the purge line or because the fuel tank filler tube cap has not been tightened correctly), the engine control module judges that there is a problem with the system and the check engine/malfunction indicator lamp illuminates.

CHECK AREA
- Engine coolant is not lower than 60° C (140° F).
- Engine speed is at between 1,600 - 3,500 r/min.
- Power steering pressure switch: OFF
- Ambient pressure is not lower than 76 kPa (11.0 psi).
- Volumetric efficiency: 20 - 80%
- Intake air temperature is not lower than -10° C (14° F)
- Pressure increase when evaporative emission purge solenoid and evaporative emission ventilation solenoid are closed is 50 mmAq or less.
- Pressure variation range is 68 mmAq or less.
- Monitoring time: 50 - 100 sec.

JUDGEMENT CRITERIA
- Internal pressure of the fuel tank has not changed more than 100 mmAq in 20 sec after the tank and vapor line were closed.

PROBABLE CAUSE
- Improper tightening of fuel tank filler tube cap
- Fuel vent valve failed
- Purge line or vapor line blocked
- Broken seal in fuel tank, purge line or vapor line
- Evaporative emission purge solenoid failed
- Evaporative emission ventilation solenoid failed
- Fuel tank differential pressure sensor failed
- Engine coolant temperature sensor failed
- Intake air temperature sensor tailed
- Power steering pressure switch failed
- Incorrect fuel used
- Improper relief pressure of fuel tank filler tube cap
- Defective seal of evaporative emission canister
- Evaporative emission canister clogged




DIAGNOSTIC CHART