2001 Suzuki Esteem Emmision control

DTC P0440: EVAP SYSTEM LEAK DETECTED, OR P0455: EVAP SYSTEM LEAK DETECTED (GROSS LEAK)
WARNING:This work must be performed in a well ventilated area away from any open flame.

Condition
With engine running, Engine Control Module (ECM) closes EVAP canister air valve and opens EVAP canister purge valve. If EVAP control system is okay, EVAP control system pressure detected by fuel pressure sensor is lowered. When EVAP control system pressure is lowered, ECM closes EVAP canister purge valve, leaving EVAP canister air valve closed. If EVAP system is okay, fuel tank pressure will increase to a predetermined level.
DTC P0440 is set when fuel tank pressure increase exceeds a predetermined value. MIL is illuminated when ECM detects malfunction during 2 consecutive drive cycles. DTC P0455 is set when fuel tank pressure change is less than predetermined. MIL is illuminated when ECM detects malfunction during first drive cycle. Possible causes are:
Missing, loose or malfunctioning fuel filler cap.
Loose or plugged vacuum hose.
Components mounted to fuel tank leaking in aria of mounting.
EVAP canister plugged.
EVAP canister purge valve malfunction.
EVAP canister air valve malfunction.
Fuel tank pressure control valve malfunction.
Fuel tank pressure sensor malfunction.
Fuel level sensor malfunction.
ECM malfunction.

Most likely causes are loose or faulty fuel cap or a damaged/broken vacuum hose !

Possible causes are:
Missing, loose or malfunctioning fuel filler cap.
Loose or plugged vacuum hose.
Components mounted to fuel tank leaking in aria of mounting.
EVAP canister plugged.
EVAP canister purge valve malfunction.
EVAP canister air valve malfunction.
Fuel tank pressure control valve malfunction.
Fuel tank pressure sensor malfunction.
Fuel level sensor malfunction.
ECM malfunction.

Hope this helps