Charcoal canister (EVAP canister)
Definition
The charcoal canister is a plastic box filled with activated carbon granules, usually near the tank, that adsorbs petrol vapour when the car is parked and releases it when the purge valve opens and fresh air is drawn through the vent valve. Its carbon lasts the car's life unless it is flooded with liquid fuel from repeatedly topping off after the pump clicks, which saturates the bed and lets carbon dust travel to the purge valve and jam it. A failed or blocked vent valve (dirt, insects, corrosion) stops the canister breathing, so the tank is hard to fill, the pump nozzle clicks off early and the EVAP self-test fails. Cracked canister housings and detached hoses are common gross-leak causes after rear impacts or off-road use. Codes: P0446/P0447/P0448 (vent control circuit), P0449 (vent valve circuit), P0455 (gross leak), P0441 (purge flow), P1450-series on Ford (unable to bleed fuel tank vacuum).
Codes often stored
- P0441Evaporative Emission System Incorrect Purge Flow
- P0446Evaporative Emission System Vent Control Circuit
- P0447Evaporative Emission System Vent Control Circuit Open
- P0448Evaporative Emission System Vent Control Circuit Shorted
- P0449Evaporative Emission System Vent Valve/Solenoid Circuit
- P0455Evaporative Emission System Leak Detected (Gross Leak)