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P0455

EVAP System Leak Detected - Large Leak.

  • Generic
  • Powertrain
  • Generic code
  • Low severity

How this code is built

P
SystemPowertrain
0
Defined bySAE, the same on every car
4
AreaAuxiliary emission controls
55
FaultThe specific fault in that area

What it means

P0455 is the generic code for a large leak detected in the evaporative emission (EVAP) system, which captures fuel vapour from the tank and feeds it to the engine. The control unit runs a leak test by sealing the system and applying vacuum or pressure. If the pressure does not hold or build as expected, or the system cannot be sealed at all, it sets this code. The most common culprit is a missing, loose or faulty fuel filler cap, but any open hose, valve or canister connection can cause it.

Symptoms

  • Malfunction indicator lamp on
  • Smell of fuel around the car or fuel filler area
  • Fuel cap warning message on some models
  • Slightly poorer fuel economy in some cases
  • Failed emissions test
  • Hissing when the fuel cap is opened, or none at all

Possible causes

  • Fuel filler cap missing, loose, cracked or with a worn seallikely
  • Cracked, split or disconnected EVAP hose or pipe, including quick-release connectorslikely
  • Purge valve stuck open or leakingpossible
  • Vent valve or shut-off valve stuck open or faultypossible
  • Damaged or cracked charcoal canisterpossible
  • Corroded or damaged filler neck, or leaking fuel tank or tank sender sealpossible
  • Faulty fuel tank pressure sensor giving a false readingrare

How to diagnose

  1. Read the stored codes and freeze frame data to see when the fault set, and check for related EVAP or fuel trim codes
  2. Check that the fuel cap is fitted, tightens properly and has an undamaged seal and sealing surface on the filler neck
  3. Visually inspect all accessible EVAP hoses, pipes, connectors and the canister for cracks, disconnections or damage, including underneath the car
  4. Check the wiring and connectors of the purge valve, vent valve and tank pressure sensor for damage or corrosion
  5. Use the scan tool's bidirectional tests, where supported, to operate the purge and vent valves and confirm they open, close and seal as commanded
  6. Check the tank pressure sensor reading against a known good reference with the system vented to atmosphere
  7. Smoke test the EVAP system at the pressure and procedure specified for the vehicle to locate the leak
  8. Inspect the fuel tank, tank seal and filler neck for corrosion, damage or leaks, as the layout varies by model

How to fix

  • Replace the fuel cap with a correct one if it is missing, damaged or not sealing
  • Repair or replace leaking or disconnected EVAP hoses, pipes and connectors
  • Replace a purge valve or vent valve that is stuck or leaking
  • Replace a cracked or damaged charcoal canister
  • Repair or replace the filler neck, tank seal or fuel tank if it is leaking
  • Replace a faulty tank pressure sensor once confirmed, then clear the codes and complete a drive cycle to confirm the repair

Can I keep driving?

Low severity

The car is normally safe to keep driving, so book it in for repair soon. If you can smell fuel strongly or see a fuel leak, get it checked promptly, as that is a fire risk.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

This code for other makes

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