EVAP vapor containmentCondition dependentReviewed July 15, 2026
P0456Evaporative emission system leak detected — very small leak
The controller detected a very small sealing loss during the evaporative-system integrity test.
Conditions that can produce P0456
These are diagnostic branches, not a ranked parts list. Prevalence and testing order depend on the exact vehicle and failure scene.
- Cap or service-port seal
- Vent/purge valve micro-leak
- Small crack, porous hose, or O-ring leak
- Leak-detection pump or pressure-sensor bias
- Intermittent debris or environmental condition
What to inspect next
- Preserve the fuel level, temperature, and soak conditions
- Inspect seals and service ports closely
- Use an approved precise leak test and adequate stabilization time
- Avoid replacing multiple EVAP parts without locating or measuring the failure
Evidence that strengthens the answer
Test conditions and repeatabilityMeasured decay or pump resultSmoke/leak locationValve sealing and sensor-zero evidence
Verify the repair
Preserve the pre-repair record, document exactly what changed, then repeat the relevant operating condition safely. Confirm no current or pending fault returns, review permanent-code and readiness state where applicable, and state which tests or modules remained unavailable.
This page explains a commonly standardized code at a general level. Confirm the exact definition, module, status, test conditions, thresholds, wiring, and service process for the vehicle application using current official information.