P0455 on Buick: How to Diagnose & Fix
Evaporative Emission Control System Leak Detected (Gross Leak)
1 Buick model · 1 documented issue · $400-$850 repair
P0455 on Buick by model: symptoms, diagnosis and fix
Unlike older vacuum-driven purge systems, the GM three-cylinder turbo platform uses an electric EVAP purge pump to draw fuel vapor from the charcoal canister into the intake during boost, when there is no manifold vacuum available. The pump's motor and control circuit fail, and the pump can also stick, which lets raw vapor slug the intake. Owners report the check engine light, gasoline smell in and around the vehicle, and in a subset of cases the engine stalling outright while driving. Failures cluster in the roughly 30,000-65,000 mile range on both the Encore GX and the platform-twin Trailblazer.
Common Symptoms
- Check engine light with fuel/gasoline odor
- Engine stalls without warning while driving
- Rough idle immediately after refueling
- Emissions readiness monitors will not set
- Vehicle fails state emissions inspection
How to Fix
Retrieve the exact code before condemning parts, since a loose or cracked fuel cap and canister vent valve faults mimic the symptom. Confirm the purge pump's electrical supply and command state with a scan tool. The real fix is replacement of the electric EVAP purge pump assembly and associated hoses, followed by an EVAP system leak test and a drive cycle to reset readiness monitors. The 8yr/80,000 mile federal emissions warranty often covers this component, so check coverage before paying out of pocket.
Sources for this issue (2)
P0455 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0455 mean on a Buick?
P0455 stands for "Evaporative Emission Control System Leak Detected (Gross Leak)." This code means your car's evaporative emission (EVAP) system has detected a large (gross) leak, so fuel vapors that should be sealed inside the fuel and vapor system are escaping into the atmosphere. The EVAP system captures gasoline vapors from the tank and routes them to the engine to be burned instead of polluting the air, and the computer periodically pressure- or vacuum-tests this sealed system. A gross leak almost always points to something obvious and easy, like a loose, missing, or bad gas cap, rather than a deep mechanical failure. It rarely affects how the car drives, but it should be fixed to pass emissions and stop wasting fuel vapor. On Buick it is documented across 1 model: Encore GX.
What are the most common causes of P0455?
The most common causes of P0455 are: Loose, missing, or improperly tightened gas cap, Worn, cracked, or failed gas cap seal, Cracked or disconnected EVAP/vapor hose, Damaged or missing fuel filler neck seal, Faulty EVAP purge valve stuck open, Failed EVAP vent valve, Cracked or damaged charcoal canister. The specific cause varies by vehicle.
How much does it cost to fix P0455 on a Buick?
Published repair estimates on Buick range from $400 to $850 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0455 on a different make?
View P0455 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.