OBD2 Code P0455: Evaporative Emission System Leak Detected (Gross Leak)
The P0455 code means Evaporative Emission System Leak Detected (Gross Leak). Estimated repair cost: $50 – $600.
✅ OK TO DRIVE (short term). Have it diagnosed at your next convenience. Monitor for new symptoms.
📋 Diagnostic Reference
| OBD2 Code | P0455 |
| Category | Powertrain |
| Severity | Check Soon |
| Repair Cost | $50 – $600 |
| Can You Drive? | ✅ Yes — diagnose at your convenience |
🔍 Symptoms
- Check Engine Light on
- fuel odor near vehicle
- no noticeable driving symptoms
⚠️ Most Likely Causes (in order of probability)
- Loose or missing gas cap
- cracked EVAP canister
- leaking EVAP purge valve
- damaged charcoal canister
- leaking fuel tank pressure sensor seal
🛠️ Diagnostic Procedure
Step 1: Tighten or replace gas cap first — this fixes about 40% of P0455 codes
Tighten or replace gas cap first — this fixes about 40% of P0455 codes
Step 2: Clear code and drive — if it returns the leak is real
Clear code and drive — if it returns the leak is real
Step 3: Perform smoke test on EVAP system
Perform smoke test on EVAP system
Step 4: Check EVAP purge valve and vent valve operation
Check EVAP purge valve and vent valve operation
Step 5: Inspect charcoal canister for cracks or fuel contamination.
Inspect charcoal canister for cracks or fuel contamination.
ASE Certified Review: This diagnostic guide has been reviewed by an ASE-certified master technician. Diagnostic steps follow industry best practices per SAE J1979 and OEM service procedures. Always verify with a qualified mechanic before performing repairs.
Technician's Notes: Most common cause: gas cap not tightened until it clicks. Always start with the $0 fix before paying for diagnostics.
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Dealerships charge $100-$200 just to scan your car and read the code. A $20 Bluetooth OBD2 scanner gives you the same information in 30 seconds — and it works with free apps on your phone. Read and clear codes yourself before deciding if you need a mechanic.
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Data Sources: Diagnostic information compiled from SAE J1979 OBD2 standards, OEM service manuals, and ASE master technician field experience. Reviewed for technical accuracy. Repair cost ranges are national estimates and vary by location. Always verify with a qualified mechanic.