The 2023 Jeep Grand Cherokee setting P0455 indicates the evaporative emission control system detected a large leak. This fifth-generation model's sophisticated emissions systems require systematic diagnosis to locate the leak source.
Understanding P0455
P0455 indicates a significant leak in the EVAP system—the network that captures fuel vapors from the tank rather than releasing them to atmosphere. "Large leak" typically means a leak equivalent to or larger than a 0.040-inch diameter hole.
Common Large Leak Sources
The most common cause is a loose, damaged, or missing gas cap. Fuel tank damage from off-road use can create leaks. EVAP canister vent valve failures allow system pressure loss. Cracked or disconnected EVAP hoses also trigger this code.
Gas Cap Inspection
Start with the gas cap—it's the simplest fix. Check the cap seal for cracks, debris, or deterioration. Verify the cap clicks and seals properly. A damaged cap costs $20-50 versus hundreds for other repairs.
EVAP System Testing
If the gas cap is good, smoke testing identifies leak locations. Introduce theatrical smoke into the sealed EVAP system and observe for escaping vapor. Common leak points include tank filler neck, canister connections, and vent valve.
Grand Cherokee Off-Road Considerations
Off-road use can damage fuel tank shields, EVAP canisters, and connecting lines mounted under the vehicle. Inspect for physical damage if the vehicle sees trail use.
Repair Costs
Gas cap replacement costs $20-50. Vent valve replacement runs $150-350. EVAP canister replacement ranges $300-600. Fuel tank repair or replacement costs $500-1,500.