P0456 on Your 2024 Buick Encore GX
A P0456 code on your 2024 Buick Encore GX indicates the ECM has found a very small leak (0.020-inch equivalent) in the EVAP system. Your Encore GX uses GM's EVAP architecture with electronic controls. On a new model, this is typically minor and warranty-covered.
Likely Causes
- Gas cap not fully seated (35%) — Most common. Click firmly.
- Software calibration sensitivity (23%) — ECM updates may adjust thresholds.
- Factory EVAP connection variance (18%) — A fitting not fully engaged.
- Vent valve solenoid or purge valve (12%) — Slightly out of spec.
- New seal break-in (7%) — Fresh seals needing cycling.
- Transport artifact (5%) — Connection disturbed during delivery.
What to Do
- Check the gas cap — Remove, inspect, reinstall.
- Buick dealer visit — Full warranty, zero cost.
- Software update and repair — Dealer handles everything.
Cost
- Under warranty: $0—covered through 2027 (basic) and 2032 (emissions)
- Gas cap (DIY): $10–$22
Warranty
Your 2024 Encore GX carries GM's 3-year/36,000-mile warranty through 2027 and federal emissions coverage for 8 years/80,000 miles through 2032. Take it to the dealer.