P0456 on Your 2024 Acura MDX
A P0456 code on your 2024 Acura MDX signals the PCM has detected a very small leak (0.020-inch equivalent) in the EVAP system. As Acura's flagship three-row SUV, the MDX uses Honda/Acura's EVAP monitoring with a canister vent shut valve to verify system integrity.
Whether you have the standard 3.5L V6 or the Type S 3.0L turbo V6, the EVAP system is the same. On a new 2024 model, P0456 is typically minor and fully covered by Acura's comprehensive warranty.
Likely Causes
- Gas cap not fully seated (35%) — The most common trigger across all vehicles. Ensure it clicks firmly.
- Software calibration sensitivity (22%) — Acura may have PCM calibration updates that adjust EVAP monitor thresholds.
- Factory EVAP connection variance (18%) — A fitting not fully engaged from assembly.
- Canister vent shut valve or purge valve (13%) — A component slightly out of spec.
- New seal break-in (7%) — Fresh seals needing thermal cycling.
- Transport artifact (5%) — A connection disturbed during delivery.
What to Do
- Check the gas cap — Remove, inspect, and reinstall firmly.
- Acura dealer visit — Full warranty coverage means zero cost for diagnosis and repair.
- Software update — Dealer applies pending calibrations and checks TSBs using i-HDS.
- Physical repair if needed — Smoke test and component replacement under warranty.
Cost
- Under warranty: $0—covered under 4-year/50,000-mile Acura warranty through 2028
- Gas cap (DIY): $15–$30
Warranty
Your 2024 MDX carries Acura's 4-year/50,000-mile basic warranty through 2028, the 6-year/70,000-mile powertrain warranty through 2030, and federal emissions coverage for 8 years/80,000 miles through 2032. There is no reason to pay out of pocket.