P0455 - Evaporative Emission Control System (EVAP) – Large Leak Detected
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0455 is an OBD-II generic code indicating that the engine control module (ECM) has detected a large leak in the Evaporative Emission Control (EVAP) system. The EVAP system's function is to trap fuel vapors before they escape into the atmosphere. The ECM performs a monitor test by sealing the system and monitoring the rate of vacuum decay or pressure loss using the Fuel Tank Pressure (FTP) sensor. A 'Large Leak' typically means an opening greater than 0.040 inches (1.016 mm) is present, preventing the system from maintaining the required vacuum/pressure levels during the test cycle.
Possible Causes
Fuel cap is loose, damaged, or incorrect (most common cause)
Faulty EVAP Vent Valve stuck in the open position
Cracked or damaged Charcoal Canister
Leaking or disconnected vacuum hoses between the intake, purge valve, and canister
Faulty Fuel Tank Pressure (FTP) sensor providing incorrect data
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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