P0456 on Your 2024 Cadillac XT5
A P0456 code on your 2024 Cadillac XT5 signals the ECM has found a very small leak (0.020-inch equivalent) in the EVAP system. On a new model with GM's EVAP architecture, this is typically minor and fully warranty-covered.
Likely Causes
- Gas cap not fully seated (35%) — Most common cause. Click firmly.
- Software calibration sensitivity (23%) — ECM updates may adjust EVAP thresholds.
- Factory EVAP connection variance (18%) — A fitting not 100% engaged from assembly.
- 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 with a click.
- Cadillac dealer visit — Full warranty, zero cost. GDS2 diagnostics and TSB check.
- Software update and repair — Dealer handles everything under warranty.
Cost
- Under warranty: $0—covered through 2028 (basic) and 2032 (emissions)
- Gas cap (DIY): $12–$28
Warranty
Your 2024 XT5 carries Cadillac's 4-year/50,000-mile basic warranty through 2028 and federal emissions coverage for 8 years/80,000 miles through 2032. Take it to the dealer at no cost.