P0455 code: Evaporative emission system leak detected — gross leak or no flow
P0455 means the controller detected a large sealing failure or an expected flow/pressure change that did not occur during the evaporative-system test. It does not identify a failed part or establish a repair price by itself.
Also searched as: large EVAP leak · gross leak code
Conditions that can produce P0455
These are diagnostic branches, not a ranked shopping list. Testing order depends on the exact vehicle and failure scene.
- Missing, loose, or non-sealing cap
- Disconnected or split vapor hose
- Vent or purge valve stuck open
- Damaged canister, filler neck, tank, or seal
- Leak-detection hardware or pressure-sensor fault
What drivers may notice
Symptoms can be absent, intermittent, or caused by another fault. Use them to preserve context—not to select a part.
- A check-engine light with normal driving
- Fuel odor that requires an immediate safety screen
- Difficulty refueling in some vent-system failures
- A loose or recently disturbed fuel cap
- No noticeable symptom
What to inspect next
- Do not operate around fuel vapor, sparks, or hot surfaces
- Perform a complete visual and cap/seal check
- Verify valve sealing and routing
- Use approved smoke pressure and protect the system from overpressure
Tests that separate the repair branches
Start with existing evidence and low-risk observations. A planning band describes diagnostic effort, not a guaranteed local price.
Record fuel level, freeze frame, companion EVAP codes, and recent refueling
EVAP tests run only under qualifying conditions, and related codes can identify the branch.
$0 with a capable scanInspect the cap, seal, filler area, and accessible hoses
Finds missing, loose, split, disconnected, or contaminated sealing points without opening the system.
$0 visual checkVerify purge and vent valve sealing and control
A valve that does not seal can look like a large leak even when no hose is open.
$100–$250 diagnostic planning bandPerform an approved low-pressure smoke or leak test
Locates a vapor leak without guessing from the code description.
$120–$300 diagnostic planning bandWhat strengthens the answer
Prove what changed
Preserve the pre-repair record, document exactly what changed, and repeat the relevant operating condition safely. Confirm that current or pending faults do not return, review permanent-code and readiness state where applicable, and state which tests or modules remained unavailable.
Possible P0455 repair ranges
These broad U.S. planning bands compare branches before tax; they are not quotes. Vehicle, access, parts, labor rate, region, related damage, and the confirmed test result control the real total.
Cap or simple seal branch
$20–$150Use the correct cap and verify the monitor instead of assuming the light will clear immediately.
Hose, purge valve, vent valve, or wiring branch
$150–$800The smoke or valve test should identify the failed path.
Canister, leak-detection pump, filler, or tank-access branch
$400–$1,800+Fuel-vapor and tank work require fire-safe procedures and exact application parts.
P0455 questions
What does P0455 mean?
The controller detected a large sealing failure or an expected flow/pressure change that did not occur during the evaporative-system test.
Does P0455 identify the broken part?
No. A missing cap or disconnected line can create this code, but a stuck valve, damaged canister/tank path, or failed test hardware can look similar. Treat fuel odor or liquid leakage as an immediate safety issue. Confirm the exact vehicle definition and test the relevant branches before ordering a part.
Is it safe to drive with P0455?
Do not use the code alone to decide whether the vehicle is safe to drive. Stop and arrange qualified help for severe drivability, flashing warning lamps, smoke, fuel odor, overheating, braking or steering changes, electrical heat, or high-voltage damage.
How much does P0455 cost to repair?
The code alone cannot produce a defensible repair price. Cost depends on the confirmed cause, exact vehicle, parts choice, labor time, local labor rate, tax, supplies, and whether related damage is present.
What should I record before clearing P0455?
Record the reporting module, stored or pending status, freeze-frame data, readiness state, related codes, symptoms, battery voltage, and unavailable evidence. Clearing first can erase the most useful failure-scene context.
Can a loose gas cap cause P0455?
Yes on a capped system, but a cap is only one possible sealing point. Hoses, purge and vent valves, the canister, tank components, and leak-detection hardware can create the same result.
This page explains a commonly standardized code at a general level. Confirm the exact definition, module, status, test conditions, thresholds, wiring, and service process for the vehicle using current official information.
See how this page earns trust.
These links are primary-source starting points for the page's scope. They do not replace the current manufacturer procedure, wiring, specification, or service information for a specific vehicle.
Publisher
ScanWrench Editorial is the working byline for this library. Joshua Black, founder and publisher, is responsible for publication decisions, disclosures, and corrections.
A reviewed date means an editorial scope and safety check. It is not an ASE credential, OEM authorization, or vehicle-specific repair approval.
Primary sources
- SAE J2012 — Diagnostic Trouble Code DefinitionsSAE International · Standardized DTC structure, definitions, and manufacturer-controlled ranges.
- SAE on-board diagnostics standards indexSAE International · Primary standards family for regulated OBD services, identifiers, and transport context.
- OBD frequently asked questionsU.S. Environmental Protection Agency · Public explanation of regulated emissions diagnostics and the malfunction indicator light.
Revision history
- Reviewed edition: claim boundaries, safety language, internal links, and cited source scope checked.
No material correction is hidden. Material additions and corrections are dated above when they occur.
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