P0455 GMC Sierra 1500
EVAP System Leak Detected (Gross Leak) · Powertrain Code · Medium · Repair: Easy
What is P0455?
A large leak has been detected in the EVAP system. Check gas cap first — if secure, look for disconnected or cracked EVAP hoses, a stuck-open purge valve, or a leaking charcoal canister.
When the GMC Sierra 1500 triggers code P0455 (evap system leak detected (gross leak)), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the GMC Sierra 1500.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your GMC Sierra 1500.
Common Causes on GMC Sierra 1500
- Gas cap missing, loose, or severely damaged
- EVAP vent solenoid stuck wide open at charcoal canister
- Large crack or disconnection in EVAP vapor line
- Fuel tank seal failure at fuel pump module gasket
- Charcoal canister cracked open from impact damage
Symptoms
- Check engine light illuminated
- Noticeable fuel smell near vehicle
- Gas cap warning light on dashboard
- Failed emissions test
- Fuel economy noticeably decreased
Notes for GMC Sierra 1500
GM truck EVAP vent solenoids stuck open are the most common cause of large leak codes. Often located near the charcoal canister behind the rear axle.