Diagnostic trouble code P0455 indicates a large leak has been detected in the Evaporative Emission (EVAP) System.  This code may be accompanied with other evaporative emission codes such as P0442 (small evap leak detected) and P0456 (very small leak detected).  Sealed fuel systems found on today's vehicles are intended to prevent unburned fuel vapors from escaping the fuel system.  Gasoline vapors, if allowed to evaporate into the atmosphere, will react chemically with sunlight and become smog.   

U.S. Vehicles built after 1995 (OBDII) will store diagnostic trouble codes, and illuminate the "Service Engine Soon" light if a leak or other problem is detected in the EVAP system.


Possible Causes:

  • Defective, loose, or missing gas cap - Check gas cap seal for cracks
  • Vapor leak in gas tank, charcoal canister, hoses, etc.
  • Defective canister vent or purge solenoid
  • Defective fuel tank pressure sensor
  • Missing or misrouted vacuum hoses


Since the EVAP system stretches from the engine compartment to the fuel filler neck, be prepared to make a complete end to end inspection of all EVAP system components. Leaks can be attributed to anything from an improperly installed gas cap to an internal sealing valve fault in a solenoid.  Improperly tightened or poorly sealing gas caps may be the largest cause of EVAP leaks.  Look closely at gas caps for damaged or cracked sealing o-rings.  It has been reported that some aftermarket gas caps do not seal properly, so be sure to look for a quality product when shopping for a replacement. 

Gas caps may be a common source for leaks, but there are plenty of other areas that could leak as well.  Any of the hoses and lines that run from the engine compartment to the charcoal canister could be a potential leak point.  


Chrysler and Dodge - Code P0455

On the Dodge Caravan, and similar models like Chrysler Town and Country and Plymouth Voyager, pay close attention to EVAP lines that run under the air filter box and around the strut tower.  Look for splits in the rubber sections where platic lines are joined together.  Follow the EVAP lines and check all areas that join together with rubber hose, especially in molder rubber sections (elbows) that make tight bends near the vapor canisters under the vehicle.  Check the vapor canister themselves for cracks.  Cracked charcoal canisters are reported as a common problem on some models of Dodge Ram trucks and Durango SUV's.  Fuel filler necks have become common leak points as vehicles get older.  Rusted filler necks are becoming a common replacement item on some models.  Diagnostic testing may reveal other common faults such as bad leak detection pumps, purge solenoids and vent solenoids.  Technicians should look at TSB #25-001-02 for more information about faulty vent valves.            



Similar Codes:

  • P0441 - EVAP System Insufficient Purge
  • P0442 - EVAP System Leak Detected
  • P0443 - EVAP System Purge Solenoid Circuit Malfunction
  • P0446 - EVAP System Vent Control Circuit Malfunction 
  • P0449 - EVAP System Vent Solenoid Circuit Malfunction
  • P0450 - EVAP System Pressure Sensor Malfunction
  • P0451 - EVAP System Pressure Sensor Performance
  • P0452 - EVAP System Pressure Sensor Low
  • P0453 - EVAP System Pressure Sensor High
  • P0456 - EVAP System Small Leak Detected
  • P0457 - EVAP System Leak Detected
  • P0496 - EVAP System Flow Detected During Non-Purge