OBD codes / P0456 / Nissan Altima
P0456 on a Nissan Altima
Evaporative Emission System Leak Detected (Very Small Leak)
All modern Altimas with EVAP monitoring.
What P0456 usually means on a Altima
P0456 is the small-leak counterpart on the Altima, caught by the tighter monitor. Because the leak is pinhole-sized, a smoke test is essentially required to find it. The gas cap seal and Nissan's vent and purge valves are the usual sources, along with hairline hose cracks. Diagnosis typically outweighs the parts cost.
Most likely causes on this model
- Weeping gas cap seal
A worn cap O-ring passes large-leak testing but fails the small-leak monitor.
- Vent or purge valve not sealing
Nissan valves that will not fully seat leak the small volume this code detects.
- Tiny hose or grommet cracks
Age-hardened lines leak just enough to trip P0456.
What it costs on a Altima
Invest in the smoke test to pinpoint the pinhole on the Altima. The parts - cap, a valve, a length of hose - are inexpensive. Expect diagnostic labor to be the larger share of a small-leak repair.
Year, engine and mileage change the answer. Get a diagnosis for your Altima — it weighs these causes against your exact configuration and real complaint data.
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Related symptoms
Nissan Altima problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0456 behavior is covered on the main P0456 page. Confirm with a scan tool before buying parts.