CarSpecFix
OBD-II trouble code

P0455: Evaporative Emission System Large Leak Detected, causes & can you keep driving?

Quick answer

What it means
Evaporative Emission System Large Leak Detected[1]
Wording from GM Service Bulletin 21-NA-124 (EVAP P0442/P0455 diagnostic tips), p.1
Can I keep driving?
It is important to note that an illuminated dashboard light, as described here, is intended to inform the driver of the need for service, NOT of the need to stop the vehicle. However, service should be sought as soon as possible.[2]
U.S. EPA Fact Sheet EPA 420-F-97-003 (May 1997), Frequently Asked Questions About On-Board Diagnostics, p.2 · applies to all OBD-II vehicles
Under certain conditions, the dashboard light will blink or flash. This indicates a rather severe level of engine misfire. When this occurs, the driver should reduce speed and seek service as soon as possible.[2]
U.S. EPA Fact Sheet EPA 420-F-97-003 (May 1997), Frequently Asked Questions About On-Board Diagnostics, p.2 · applies to all OBD-II vehicles
Toyota only If the malfunction indicator lamp comes on while driving First check the following: Is the fuel tank empty? If it is, fill the fuel tank immediately. Is the fuel tank cap loose? If it is, tighten it securely. The light will go off after several driving trips. If the light does not go off even after several trips, contact your Toyota dealer as soon as possible.[3]
Toyota only When "Check Fuel Cap" is displayed on the multi-information display: The fuel tank cap may be unfastened or loose. Turn the engine switch off, check the cap and tighten it securely.[3]
Toyota only Malfunction indicator lamp ... Indicates a malfunction in: The electronic engine control system; The electronic throttle control system; or The electronic automatic transmission control system → Have the vehicle inspected by your Toyota dealer immediately.[3]
How urgent?
Not rated
Severity is rated only when a source states it.
Shop visit or check it yourself first?
Not yet verified — source pending
Last verified 2026-10-15Report a data error

Possible causes

Each cause comes from a manufacturer document and applies to the models listed. Your vehicle may differ.

  1. GM's tech tip (GM Service Bulletin 21-NA-124 (EVAP P0442/P0455 diagnostic tips), p.1) [1]
    Large leak or purge blockage: unseated EVAP tube connection
  2. GM's tech tip (GM Service Bulletin 21-NA-124 (EVAP P0442/P0455 diagnostic tips), p.1) [1]
    Damaged EVAP tube/line
  3. GM's tech tip (GM Service Bulletin 21-NA-124 (EVAP P0442/P0455 diagnostic tips), p.1) [1]
    Canister vent valve stuck open
  4. GM's tech tip (GM Service Bulletin 21-NA-124 (EVAP P0442/P0455 diagnostic tips), p.1) [1]
    Purge valve stuck closed
  5. GM's tech tip (GM Service Bulletin 21-NA-124 (EVAP P0442/P0455 diagnostic tips), p.1-2) [1]
    Fuel tank cap not closed properly (one of 7 connections to inspect)
  6. Honda/Acura's service bulletin (Honda/Acura service bulletin (i-HDS), MC-10219672, p.1) [4]
    Fuel filler pipe main flap unit stuck open

Sources

  1. GM Service Bulletin 21-NA-124 (EVAP P0442/P0455 diagnostic tips), p.1, retrieved 2026-10-15
  2. U.S. EPA Fact Sheet EPA 420-F-97-003 (May 1997), Frequently Asked Questions About On-Board Diagnostics, p.2, retrieved 2026-10-15
  3. 2022 Toyota Camry Owner's Manual OM06244U, p.533, retrieved 2026-10-15
  4. Honda/Acura service bulletin (i-HDS), MC-10219672, p.1, retrieved 2026-10-15

General information from manufacturer documents, not professional mechanical advice. See Data sources.