OBD-II FAULT CODE

P0455: Evaporative emission system leak detected (gross leak / no flow)

Evaporative emissionsGeneric powertrain

The EVAP monitor has detected a gross leak or a no-flow condition. A loose fuel cap is one possibility, not a complete diagnosis.

Possible causes

Examples to investigate; this list is not a probability ranking or a diagnosis.

Missing or unsealed fuel cap where fitted
Disconnected or damaged vapour line
Purge or vent system malfunction

Symptoms you might notice

Check-engine light
Possible fuel odour

Diagnostic approach

Inspect the filler closure and visible EVAP connections.
Review related codes and commanded purge/vent behaviour.
Use the vehicle-specific leak/flow diagnostic procedure with approved equipment.

Save codes and freeze-frame information before clearing anything. A cleared warning light does not prove that a repair worked; the applicable monitor must run again.

Possible repairs — after testing

Restore a confirmed leaking connection or filler seal.
Repair the verified purge, vent or flow fault.

Related codes

P0442 · Evaporative emission system leak detected (small leak) →

This is general diagnostic orientation, not a manufacturer-specific repair procedure. A qualified technician can confirm test conditions and safe working methods.