P0455 on GMC: How to Diagnose & Fix
Evaporative Emission Control System Leak Detected (Gross Leak)
1 GMC model · 2 documented issues · $20-$350 repair
P0455 on GMC by model: symptoms, diagnosis and fix
P0442 on the Sierra 1500 is a small EVAP leak detected during the ECM's key-off/idle vacuum test. On these trucks the two most common real-world causes are a loose, worn, or cracked gas cap seal (the cheapest fix and always the first check) and — a documented GM issue (TSB 15-NA-019) — the fuel tank filler vent hose connector cracking, which allows vapor to escape and sets P0442 (and sometimes P0455). The vent hose fracture is addressed by replacing the vent hose assembly (part No. 22802073 on 2013-2015 models). The EVAP purge valve (engine bay) and vent solenoid (near the tank) can also weep. Drivers often notice a faint fuel odor and the CEL, with no drivability change.
Common Symptoms
- Check engine light
- Faint fuel/gasoline odor
- No drivability change
- Occasional failed emissions test
How to Fix
Start with the gas cap — inspect the seal and tighten/replace with OEM. If the code persists, perform a smoke test to pinpoint the leak; inspect the fuel filler vent hose connector for cracks and replace the vent hose assembly if fractured. Replace the purge or vent solenoid if the smoke test isolates it there.
Sources for this issue (1)
P0455 indicates a large (gross) EVAP leak — the ECM cannot pull or hold vacuum in the evaporative system at all. On the Sierra 1500 the classic causes are a completely missing/unsealed gas cap, a stuck-open or failed EVAP vent solenoid (mounted under the truck near the fuel tank/spare tire, where it's exposed to road spray, dirt, and corrosion), and a cracked or disconnected vapor/vent hose. Because the vent solenoid sits at the canister under the bed, water intrusion and corrosion cause it to stick open, which the ECM reads as a wide-open system; a tell-tale symptom is the fuel nozzle repeatedly clicking off during refueling. The filler vent hose connector fracture noted in GM literature can also escalate to P0455. Symptom-wise the driver usually sees only the CEL, sometimes a fuel smell, and no performance loss.
Common Symptoms
- Check engine light
- Fuel vapor smell
- Missing or loose gas cap
- Fuel nozzle clicks off repeatedly when refueling
- Fails emissions test
How to Fix
Confirm the gas cap is present and sealing. Smoke-test the EVAP system to find the large leak. The most common repair on these trucks is replacing the under-body EVAP vent solenoid/valve at the canister; also inspect and replace cracked vapor lines and the fuel filler vent hose. Clear codes and run the EVAP monitor to confirm.
Sources for this issue (1)
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 GMC?
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 GMC it is documented across 1 model: Sierra 1500.
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 GMC?
Published repair estimates on GMC range from $20 to $350 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.