System: Powertrain (P-Code)
SAE Standard (Generic)
Family: EVAP Small Leak
Code P0456: EVAP System Leak Detected (very small leak)
Diagnostic & Technical Explanation
Code P0456 (EVAP System Leak Detected (very small leak)) sets when the EVAP leak-detection monitor cannot hold vacuum or pressure in the fuel vapor system within its small-leak threshold (typically a 0.020 in. equivalent orifice), including the tighter very-small-leak threshold and the fuel-tank-side/fresh-air-side variants used on natural-vacuum leak detection systems, or when the general EVAP system monitor itself fails. The dominant causes are a loose or worn fuel filler cap, a cracked EVAP hose, or a purge/vent solenoid that no longer seals.
First-listed procedure
Rank #1
Inspect and reseat or replace 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 Small 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)