P0456Powertrain
Powertrain · SAE
EVAP System Leak Detected (Very Small Leak)
Meaning
The ECU has detected a very small leak in the evaporative emissions system. This is the finest sealing threshold monitored and indicates a micro-leak that is hard to find by eye.
Common causes
- Micro-leak at the fuel-cap seal or a hose
- EVAP valve seal that does not close perfectly
- Fuel cap not fully tightened
- Hairline crack at a canister connection
- Slightly aged O-rings or EVAP connection
Symptoms
- Check-engine light on
- Often no other noticeable symptom
- Rarely a faint fuel smell
- No effect on drivability
- Possible emissions-test failure
Severity
Moderate: an emissions micro-leak with no immediate mechanical risk at all.
What to do
- Fully tighten the fuel cap and inspect its seal carefully
- Run a smoke test to reveal a very small leak
- Inspect the O-rings, connections and EVAP valve seals
- Replace the cap or the suspect component and repeat the leak test