P0455 Code: Toyota Tacoma (2016-2023) - Causes, Symptoms & Fixes

P0455 Diagnostic Guide for 2016-2023 Toyota Tacoma (EVAP Large Leak)

Notes on data limitations

• REAL NHTSA data provided for this specific vehicle/issue combination shows no owner complaints and no recalls in the database. No recalls found in NHTSA database.
• Because there are no officially documented complaints/recalls in the data you supplied, this guide relies on general OBD-II EVAP knowledge plus Toyota-specific tendencies from broad automotive experience. If you have a vehicle-specific TSB or campaign, it isn’t reflected in the data you supplied.

CODE MEANING AND SEVERITY

• Code definition: P0455 – Evaporative Emission Control System Large Leak Detected
• What it means: The vehicle’s EVAP system detected a leak large enough to trigger the ignition, typically when the engine is running and the system pressure test indicates a big loss of sealedness. The malfunction usually sets the MIL (check engine light) and can be accompanied by a noticeable fuel odor or reduced EVAP system function.
• Severity: Moderate to high. A large leak can allow fuel vapors to escape, may indicate a failed EVAP component, and can affect emissions, fuel economy, and readiness for inspections. It may or may not immediately affect drivability, but you’ll want to diagnose and repair promptly to avoid emissions failures and potential fuel odor.

COMMON CAUSES ON TOYOTA TACOMA (2016-2023)

• Loose, cracked, or missing fuel cap (the most common, simplest fix)
• Damaged or deteriorated EVAP hoses and vacuum lines (cracks, splits, or disconnected hoses)
• Faulty EVAP purge valve (solenoid) or its wiring
• Leaking or failed charcoal canister or vent valve
• Cracked or damaged fuel filler neck or ground clamps
• EVAP system fittings or clamps that have rusted loose or corroded
• Storage/retention-related issues: a leak in the EVAP system plumbing after the canister
• LES or DLC-related wiring or connector corrosion in the EVAP circuitry (less common but possible)
  Note: In Tacomas, the gas cap and EVAP hoses are among the most frequently implicated items for P0455 presentations.

SYMPTOMS

• Check Engine Light (MIL) illuminated
• Noticeable fuel odor around the vehicle or fuel filler area
• Possible minor reduction in fuel economy or performance if the system is under pressure
• No obvious drivability issues (P0455 often doesn’t affect power or idle directly, unlike some other engine codes)
• In some cases, a failed or stuck purge valve can cause rough idle or stalling if the leak interacts with the intake manifold vacuum

DIAGNOSTIC STEPS (P0455 on a 2016-2023 Toyota Tacoma)

Prepare with tools: OBD-II scanner, basic hand tools, inspection mirror, flashlight, possibly a smoke machine or certified EVAP smoke tester.

Step-by-step:

Confirm and reset: With car off, check that the fuel cap is on tight, then reset the MIL with the scan tool and drive or cycle the ignition to see if the code returns. A transient leak might clear if corrected (e.g., tightening the gas cap).

Visual inspection:

• Gas cap: inspect for cracks, missing/damaged seal, visible damage to the threads; replace if in doubt.
• EVAP hoses and vacuum lines: look for cracks, splits, soft spots, dryness, or loose clamps; inspect under the hood and around the charcoal canister.
• EVAP purge valve and wiring: check for corrosion, damaged connectors, or melted insulation.
• Filler neck, intake connections, and clamps: ensure connections are tight and components are in good condition.

Perform a functional check:

• Purge valve operation: with the engine running, test the purge valve (via scan tool or manually exercising the valve) to see if it clicks and changes the system’s behavior. A stuck or faulty purge valve can cause EVAP inconsistencies.
• Check for vacuum leaks: use a hand vacuum pump or the “prop test” method to see if the system holds vacuum; listen for hissing or use a sprayer/string to locate leaks (avoid spraying near hot components).

Evap system leak test:

• Smoke test (preferred): Introduce smoke into the EVAP system and observe where smoke escapes. This quickly locates large leaks in hoses, canister, and fittings.
• If a smoke tester isn’t available, perform a balance test by sealing off the canister and pressurizing the system with a known-good source to identify the leak location, but this is less precise.

Inspect canister and vent components:

• If hoses and cap test clean, the charcoal canister or vent valve may be leaking or failed. Inspect for wet/damp canister housing, cracking, or a visible leak around the canister.

Special tests:

• If allowed by your diagnostic procedure, perform a system pressure test (EVAP test) using a scan tool that commands the EVAP system or a dedicated EVAP test port. Look for abnormal drop in pressure.
• Check for related codes (P0440, P0442, P0446, etc.) that may indicate partial EVAP faults or secondary issues. A P0455 can sometimes accompany another EVAP fault if the large leak criterion isn’t verified on first inspection.

Road test after repairs:

• Clear codes and drive normally for a few cycles (engine on, engine off) to ensure the code does not return and the EVAP readiness monitors complete.

Tips:

• A common path to a P0455 is a simple gas cap fix. Always start with the gas cap and cap seal replacement.
• If the vehicle has a hard-to-find leak, a professional smoke test is highly recommended for accuracy.
• After any repair, clear the code and perform an OBD readiness/monitor test to confirm the EVAP monitor runs and completes.

RELATED CODES

• P0450 – Evaporative emission system pressure sensor fault
• P0451 – Evaporative system pressure sensor range/performance
• P0452 – Evaporative system pressure sensor low input
• P0440 – Evaporative emission system malfunction (generic base code; often indicates an EVAP problem)
• P0442 – Evaporative system small leak detected (smaller leak, often around a loose cap or hose)
• P0443 / P0444 – EVAP purge solenoid troubles (and related circuitry)
• P0446 – Evaporative emission system vent valve control circuit

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices vary by region, shop, and whether you provide parts. These ranges reflect typical consumer market estimates as of 2025. Labor rates commonly range from $90–$140 per hour in many markets; higher in dealer or specialized shops.

• Gas cap replacement

  • Parts: $5–$40
  • Labor: $0–$30 (often a DIY replacement)
  • Typical total: $5–$70

• EVAP hoses/lines and clamps

  • Parts: $20–$120 (depending on length and number of hoses)
  • Labor: 0.5–2 hours
  • Typical total: $120–$350

• EVAP purge valve (solenoid) replacement

  • Parts: $40–$180
  • Labor: $60–$180
  • Typical total: $100–$360

• Charcoal canister replacement

  • Parts: $100–$600 (can vary by model and whether OE or aftermarket)
  • Labor: 2–4 hours
  • Typical total: $300–$1,400

• Filler neck or vent valve repair/replacement

  • Parts: $20–$150
  • Labor: 0.5–2 hours
  • Typical total: $100–$450

• EVAP system diagnostic / smoke test

  • Diagnostic fee: $50–$150 (often waived if you proceed with repair at the same shop)
  • Smoke test equipment usage: typically included in diagnostic or part of the repair estimate

Notes:

• In many cases, the root cause is a simple gas cap or a cracked hose; addressing these first is common and cost-effective.
• If multiple EVAP components are aged or damaged, expected total repair can be toward the higher end of these ranges.
• Some Tacoma-specific parts availability or pricing can vary; dealer pricing tends to be higher than independent shops.

DIY VS PROFESSIONAL

• DIY suitability:

  • Gas cap replacement: very DIY-friendly; inexpensive and quick.
  • Visual hose inspection: feasible for a motivated DIYer with basic tools.
  • Small HVAC/EVAP hose replacement: doable if you’re comfortable with under-hood work; ensure the system is depressurized before opening lines.
  • Smoke test: usually not DIY unless you own or borrow a basic smoke machine; the test is highly effective but requires proper equipment and safety considerations.
  • Pros: lower cost, faster turnover, learning experience.

• When to go pro:

  • If you suspect the charcoal canister, vent valve, or fuel tank components, or if there’s a persistent leak with no obvious visual cause.
  • If no gas cap or hose issue is found, or if the leak is behind the canister or inside the EVAP system.
  • If a smoke test or EVAP pressure test is needed for precise locating of leaks.
  • Pros: accurate leak localization, proper sealing of high-pressure components, emissions compliance.

• What a professional will do:

  • Smoke test or pressure test to locate the large leak quickly.
  • Inspect EVAP purge valve, vent valve, and sensor circuits with proper equipment.
  • Replace defective components and perform EVAP readiness monitor tests to ensure resets and proper operation.
  • Clear codes and verify the repair via drive cycles.

PREVENTION

• Regularly check and replace the gas cap if the seal or threads are worn.
• Inspect EVAP hoses and clamps during routine maintenance or if you notice a fuel smell.
• Use a high-quality fuel and keep the filler area clean to avoid contamination or cap residue.
• When performing maintenance on the EVAP system, use OEM or high-quality aftermarket hoses and valves to minimize premature failures.
• Promptly address any MIL/CHECK ENGINE light related to EVAP problems to avoid failing emissions tests and possible warranty concerns.
• If you frequently drive in harsh environments (dusty, humid, or salted roads), inspect EVAP components after winter or salt exposure, as corrosion and cracking can lead to leaks.

Summary

• P0455 indicates a large EVAP leak. In the 2016-2023 Toyota Tacoma, common culprits include the gas cap, hoses, purge valve, and charcoal canister.
• Start with the simplest fix (gas cap) and proceed through a visual inspection of hoses and valves.
• For persistent leaks or when visual inspection fails to locate the leak, a professional smoke test is highly recommended to pinpoint the exact location.
• Repair costs can range from inexpensive gas cap fixes to more substantial EVAP component replacements. Budget roughly $100–$600 for common fixes, with canister-related repairs potentially higher.
• With no recalls or complaints in the provided data, treat this as a standard EVAP issue and focus on proper diagnosis to avoid emissions-related problems.