What does OBD2 code P0455 mean?
The engine control module (ECM) or powertrain control module (PCM) sets code P0455 when it registers that the Evaporative Emission System Leak Detected (Gross Leak) performance has fallen below the manufacturer's required baseline. This triggers your vehicle's malfunction indicator lamp (MIL), commonly known as the Check Engine Light.
Is It Safe to Drive with Code P0455?
Yes, it is safe to drive. The EVAP system prevents fuel vapors from escaping into the atmosphere. A leak will not affect engine performance, but it is an environmental concern and will prevent you from passing emissions tests.
Symptoms of OBD2 Code P0455
Depending on your car model, symptoms for P0455 may vary. The most typical symptoms include:
- Check Engine Light (MIL) illuminated
- Slight fuel odor around the vehicle when parked
- No direct engine performance issues
What Causes Code P0455?
A variety of physical faults can trigger the P0455 code. Here are the most frequent culprits:
- Loose, cracked, or missing gas cap (most common)
- Faulty EVAP Purge Valve or Vent Valve
- Cracked charcoal canister or damaged EVAP hoses
- Leaking fuel filler neck seal
Step-by-Step Diagnostic Routine
Before replacing any expensive components, run through these standardized troubleshooting steps:
- Check the gas cap. Remove it, clean the seal, reinstall it, and ensure it clicks securely. Clear the code and see if it returns.
- Use OBDAssistant to run an EVAP system monitor test if supported by your vehicle.
- Visually inspect EVAP lines under the hood and near the fuel tank for splits or damage.
- Perform a smoke test of the EVAP system to pinpoint the location of the escaping vapor.
Expected Repair Costs for P0455
A new gas cap costs $10 - $30. EVAP purge or vent valves cost $80 - $200. Replacing charcoal canisters or major EVAP lines ranges from $200 to $600.
Save on Diagnosis with OBDAssistant
OBDAssistant lets you clear the code after checking the gas cap and monitors the EVAP system readiness monitors to verify if the issue is resolved without waiting weeks for the ECU to complete its automatic checks.
Frequently Asked Questions
It means the system detected a large opening (usually larger than 0.09 inches) that prevents the fuel tank from holding a vacuum.
Yes, a loose, damaged, or unclicked gas cap is the single most common cause of a gross EVAP leak.
No, it will not affect engine fuel consumption or performance, but you will lose tiny amounts of fuel to evaporation.
You can clear it using OBDAssistant after tightening your gas cap or replacing a faulty vent valve.
It is the Evaporative Emission Control system, which traps and recirculates fuel vapors from the gas tank so they aren't released into the air.