OBD-II Code · Powertrain
P0455
EVAP System — Large Leak Detected
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$5–$300
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
EVAP system large leak — usually missing or loose gas cap.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Fuel smell sometimes
Likely causes
- Loose / missing fuel capMost common
- Damaged filler neck
- Disconnected EVAP hose
- Failed vent valve
Read the full diagnostic procedureP0455 means the EVAP system has detected a large leak, defined as a leak equivalent to a 0.040 inch (1.0 mm) orifice or larger, which the system test…
P0455 means the EVAP system has detected a large leak, defined as a leak equivalent to a 0.040 inch (1.0 mm) orifice or larger, which the system tests by either pulling vacuum on the sealed system and watching it bleed off, or by pressurizing with a small pump and monitoring decay.
The number-one cause by a wide margin is a loose, missing, damaged, or wrong-fit fuel cap
check the cap first, reinstall it tight (three clicks on a clicker-style cap), clear the code, and drive a couple of drive cycles. If the cap is fine, look at the filler neck for rust holes around the cap sealing surface (extremely common on 10+ year old vehicles in salt states). Next cheapest is a visual inspection of all EVAP lines from tank to engine bay for cracks, disconnections, and rodent-chewed hoses. If still unresolved, perform a smoke test by introducing low-pressure smoke (typically 0.5 to 1.0 psi, less than 15 inH2O / 0.5 inHg) into the EVAP service port and watching for smoke escape; for healthy vehicles the EVAP system should hold vacuum better than 7 to 10 inH2O for at least 30 seconds during the natural-vacuum or pressure test. Caveat: an aftermarket or wrong-application fuel cap will set P0455 even when fully tightened because the seal geometry differs; always verify the cap is the correct OE-equivalent part.
Vehicle-specific patterns1999 to 2007 Chevrolet/GMC Silverado/Sierra/Tahoe sets P0455 routinely from a cracked or loose fuel cap, but also from the EVAP vent valve mounted ne…
- 1999to 2007 Chevrolet/GMC Silverado/Sierra/Tahoe sets P0455 routinely from a cracked or loose fuel cap, but also from the EVAP vent valve mounted near the frame rail clogging with dirt and failing to seal, GM TSB 04-06-04-051 covers the updated dust-shielded vent valve.
- 2002to 2008 Subaru Forester/Outback/Legacy is notorious for cracked carbon canisters from highway-debris impact under the rear of the vehicle, requiring full canister replacement.
- 2005to 2010 Ford F-150 sets P0455 from the EVAP canister-to-fuel-tank line cracking near the frame crossmember.
- 2004to 2009 Toyota Sienna/Highlander trips P0455 from a deteriorated fuel-filler-neck check valve seal.
Estimated repair$5 to $450.
Look up another code
P0455 — frequently asked
What does a P0455 code mean?
EVAP system large leak — usually missing or loose gas cap.
What causes a P0455 code?
Common causes: Loose / missing fuel cap; Damaged filler neck; Disconnected EVAP hose; Failed vent valve.
What are the symptoms of a P0455 code?
Typical symptoms: Check engine light; Fuel smell sometimes.
Is it safe to drive with a P0455 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $5-$300.
How do I diagnose a P0455 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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