System: Powertrain (P-Code)
SAE Standard (Generic)
Family: EVAP Large Leak
Code P0455: EVAP System Leak Detected - Large Leak
Diagnostic & Technical Explanation
Code P0455 (EVAP System Leak Detected - Large Leak) sets when the EVAP leak-detection monitor detects a leak far larger than the small-leak threshold (roughly equivalent to a 0.040 in. orifice or bigger), including the fuel-tank-side and fresh-air-side variants on natural-vacuum leak detection systems. This points to a substantially open path to atmosphere: a fuel cap left off or badly damaged, a disconnected or split EVAP hose, or a canister/valve that has failed open.
First-listed procedure
Rank #1
Check for a missing, damaged, or off-track fuel filler cap
Easy DIY
This is the first procedure in the authored
consideration order, not a measured cause likelihood. Execute it only when its prerequisites
and diagnostic findings support it. Its cost and labor estimates (where known), the step-by-step procedure and the
remaining 3 procedure(s) are in the licensed dataset. Ordering context.
Full family: EVAP Large Leak
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)