P0455
System
Powertrain (Emissions/EVAP)
Scanner required
Basic OBD2 code reader (engine codes, live data, smog readiness)

EVAP System Leak Detected (Large Leak)

Understand P0455, common causes, and the right TOPDON scanner to diagnose it.

A large leak in the EVAP system was detected — often a gas cap left off after refueling, but can also mean a disconnected or broken EVAP line.

Common symptoms

  • Check engine light shortly after refueling
  • Possible fuel vapor smell

Typical causes

  • Gas cap not tightened or missing
  • Disconnected EVAP hose
  • Damaged filler neck
  • Failed vent valve

What scanner do you need?

Basic OBD2 code reader (engine codes, live data, smog readiness)

Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.

Diagnostic tips

  • Record freeze frame data when the code first sets
  • Clear the code only after fixing the root cause
  • Check for related pending codes that point to a common issue
  • Verify battery voltage is above 12.4V before chasing sensor codes

Recommended TOPDON scanners

Frequently asked questions

Can I diagnose P0455 with a basic code reader?
Yes — P0455 is typically accessible with a basic OBD2 code reader like the TOPDON ArtiDiag201 or TopScan Lite. Live data helps confirm the repair.
Is it safe to drive with P0455?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.