P0455 Code: Honda Accord (2018-2023) - Causes, Symptoms & Fixes

2018-2023 Honda Accord: Diagnostic Guide for OBD-II Code P0455 (EVAP Large Leak)

Data context and limitations

• Real NHTSA data for Honda Accord (2018-2023) shows no owner complaints for P0455 and no recalls found in the NHTSA database.
• Recalls: No recalls found in NHTSA database
• This guide uses general automotive EVAP knowledge and Honda-specific tendencies where relevant, but statistical context is limited by the lack of NHTSA complaint data for this exact model/year/issue. Use this as a diagnostic and repair guide, not a statistical survey.

CODE MEANING AND SEVERITY

• Code P0455 = Evaporative Emission System Large Leak Detected.
• What it means: The engine computer detected a significant leak within the EVAP system, which stores fuel vapors from the tank and routes them to the engine for combustion. A large leak can be caused by damaged hoses, a cracked canister, a faulty purge or vent valve, a loose or faulty gas cap, or a compromised filler neck.
• Severity: Not typically a direct drivability issue, but it will illuminate the check engine light and often fails an emissions test. If left unresolved, it can lead to reduced fuel efficiency, potential vapor smells, and increased emissions. Repairs can range from inexpensive cap replacements to costly EVAP canister or hose replacements.

COMMON CAUSES ON HONDA ACCORD (2018-2023)

• Bad or loose gas cap (most common and lowest-cost fix)
  • Worn gasket, incorrect torque, or a cap that won’t seal properly can trigger P0455.
• Faulty EVAP purge valve or vent valve
  • Valve stuck open/closed or electrical fault can cause a large leak signal.
• Leaking or damaged EVAP hoses and fittings
  • Cracked, cracked, or disconnected hoses (especially near the purge valve, canister, or underbody areas) can create a large-capacity leak.
• Leaking charcoal canister
  • The canister can crack or deteriorate, particularly with aging, road debris, or heat exposure.
• Leaking or damaged fuel filler neck or associated hoses
  • Cracks or loose connections in the filler neck or vent lines can allow vapor leaks.
• EVAP system components not seated or damaged during repairs
  • Vacuum references, clamps, or retainers that are loose can cause leaks.
• Less common: defective EVAP system pressure sensor or wiring (if equipped with a sensor that monitors pressure in the system)
• Note: On Hondas, EVAP-related issues are a frequent source of P0455, but any large EVAP leak in the system can trigger the code regardless of brand.

SYMPTOMS

• Illumination of the Check Engine Light (CEL) or MIL (Malfunction Indicator Lamp) with code P0455 stored.
• Smell of gasoline around the vehicle or near the fuel filler area (not always present).
• Possible minor loss of fuel economy or running efficiency if the leak affects vapor management.
• No noticeable driveability problems in many cases, but some drivers report subtle roughness or hesitation if the EVAP system is tied to engine load signals.
• Emissions readiness/failure: Vehicle may fail an emissions test due to the EVAP fault.

DIAGNOSTIC STEPS

Important: Always prioritize safety when working around fuel vapors and the EVAP system. If you’re unsure, seek a qualified technician.

• Step 1: Verify and document

  • Use an OBD-II scanner to confirm P0455 and note freeze-frame data and any related codes (P0450, P0451, P0452, etc., which can indicate related EVAP issues).
  • Check for any pending codes and monitor readiness status after clearing codes.

• Step 2: Inspect the gas cap

  • Ensure the gas cap is the correct cap for the vehicle and is seated properly. Tighten to the recommended torque (often a simple quarter-turn after finger-tight is typical; don’t overtighten).
  • Inspect the cap gasket for cracks or damage; replace if in doubt.

• Step 3: Visual inspection of EVAP system components

  • Inspect all visible EVAP hoses and connections for damage, cracks, loose clamps, or disconnections, especially near the purge valve, vent valve, and canister.
  • Inspect the fuel filler neck and the area around the neck for cracks or damage.
  • Look for signs of gasoline seepage or wetness around the canister area (underbody shield areas may hide components).

• Step 4: Inspect purge and vent valves

  • With the engine off, disconnect electrical connector(s) and check for obvious signs of damage or corrosion. When possible, test valve operation with the engine running and the purge/vent valve commanded (note: some tests require special tools and a scan tool to command the valve).

• Step 5: Smog-test/EVAP diagnostic test

  • A smoke machine is the most effective tool to locate EVAP leaks. If a smoke test is available, introduce smoke into the EVAP system and observe where it escapes.
  • If a smoke machine isn’t available, a professional-grade EVAP pressure test can reveal leaks via a pressure test port.

• Step 6: Targeted component testing

  • If the gas cap and hoses appear intact, test the purge valve and vent valve for proper operation (leaking valves or valves stuck in one position can cause large leaks or erroneous readings).
  • Inspect the charcoal canister for cracks or moisture intrusion.

• Step 7: System performance and readiness

  • After repairs, clear codes and perform a drive cycle to allow or verify the EVAP monitor completes. Check if P0455 returns.

• Step 8: If the fault persists

  • Consider a full EVAP system diagnostic by a shop with a smoke test machine and service manual. Persisting P0455 with a confirmed large leak often requires component replacement (hose(s), purge valve, vent valve, or canister) and resealing of the system.

RELATED CODES

• P0450: Evaporative Emission System Pressure Sensor/Switch Short/Intermittent/High
• P0451: EVAP System Pressure Sensor Range/Performance Problem
• P0452: EVAP System Pressure Sensor Low Input
• P0453: EVAP System Pressure Sensor High Input
• P0454: EVAP System Pressure Sensor Intermittent
• P0456: EVAP System Small Leak Detected (distinct but related in EVAP family)
• Note: Related codes point to various levels of leaks or sensor faults within the EVAP system. Investigating P0455 often involves confirming no large leaks exist while also checking sensor integrity.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices are approximate and can vary by region, shop, and whether you use OEM or aftermarket parts. Labor rates in many areas range from roughly $90–$180 per hour.

• Gas cap replacement

  • Parts: $10–$40
  • Labor: $0–$20 if DIY; $40–$80 if done at a shop
  • Typical total: $20–$100
  • When to do: First step for P0455; inexpensive and often effective if the seal is worn.

• EVAP hose replacement (visible, less complex sections)

  • Parts: $20–$120 (per hose, depending on length and material)
  • Labor: 0.5–2 hours
  • Typical total: $100–$400

• EVAP purge valve replacement

  • Parts: $50–$180
  • Labor: 1–2 hours
  • Typical total: $150–$500

• EVAP vent valve replacement

  • Parts: $60–$200
  • Labor: 1–2 hours
  • Typical total: $180–$600

• Charcoal canister (EVAP canister) replacement

  • Parts: $250–$700
  • Labor: 2–4 hours
  • Typical total: $600–$1,600
  • Notes: Canister failures are among the more expensive EVAP repairs.

• Fuel filler neck or related fuel-line components

  • Parts: $100–$400
  • Labor: 1–3 hours
  • Typical total: $300–$1,000

• EVAP system diagnostic service (smoke test or pressure test)

  • Parts: N/A (diagnostic charge)
  • Labor: 0.5–2 hours
  • Typical total: $100–$350

• miscellaneous clamps, connectors, gaskets

  • Parts: $5–$50
  • Labor: often included in overall diagnosis or repair
  • Typical total: $20–$150

• Summary guidance

  • If the only symptom is a loose gas cap, fixable in minutes with minimal cost.
  • If hoses or valves are involved, costs rise with complexity.
  • A full canister replacement is the most expensive EVAP repair and will often drive the total cost higher than other fixes.

DIY vs PROFESSIONAL

• DIY opportunities (suitable for many owners)

  • Replace gas cap: easy, low risk, and inexpensive.
  • Inspect and tighten/replace simple hoses you can reach without removing major components.
  • Clear code after addressing a known issue and monitor to confirm it doesn’t return.
  • Basic diagnostic checks (visual inspection, check for broken clamps) can be DIY-friendly.

• When to go professional

  • Gas cap is not the issue or the code returns after replacement.
  • Suspect a hidden leak: requires a smoke test or specialized EVAP diagnostic tools.
  • Suspect purge/vent valves or a canister failure.
  • There is a risk in attempting to diagnose or bypass EVAP leaks without proper tools, as the system is designed to manage gasoline vapors and can be hazardous.

• What to expect from a shop

  • Smoke testing to pinpoint leaks
  • Pressurizing the EVAP system and checking the manifold for leaks
  • Replacing failed components with OEM or aftermarket parts
  • Clearing codes and confirming the EVAP monitor passes

PREVENTION

• Regularly inspect and replace the gas cap if the seal or gasket shows wear; ensure proper seating every fill.
• Inspect visible EVAP hoses and connections annually or during routine maintenance; replace any damaged hoses promptly.
• Avoid filling beyond the first click and don’t top off the tank, which can flood the EVAP system.
• Keep the area around the fuel filler neck clean and free from debris that could cause damage or leaks.
• Address minor EVAP symptoms early (smells, MIL on) to prevent the issue from worsening into a large leak.
• If you perform any maintenance on the fuel system, ensure all clamps and hoses are properly re-seated and secured after the work.

Closing note on data limitations

• The guidance above is grounded in general EVAP knowledge and Honda Accord tendencies. The absence of NHTSA complaints and recalls for this issue/model/year in the provided data means there is no model-specific complaint trend to rely on here. Always verify with a current service manual and local diagnostic data, and consult a qualified technician if you’re unsure about performing EVAP repairs yourself.

If you’d like, I can tailor the diagnostic steps to your exact symptoms (MIL status, any smell, recent fuel fill, visible leaks) or provide a step-by-step workflow for a quick at-home check.