P0446 Code: Honda Accord (2018-2023) - Causes, Symptoms & Fixes

Official recalls

• No recalls found in NHTSA database

Code overview for 2018-2023 Honda Accord

CODE MEANING AND SEVERITY

• P0446 = Evaporative Emission (EVAP) Vent Control System Malfunction. The ECM/PCM has detected a fault in the control circuit for the EVAP vent valve, which is responsible for venting fuel vapors from the charcoal canister to the intake manifold as part of the EVAP system.
• Severity and impact: Emission-related code. The MIL (Check Engine Light) is typically illuminated. A P0446 can affect fuel economy and may cause an emissions test failure. In some cases the vehicle runs normally aside from the warning light; in others, you may notice drivability or idle concerns if the EVAP circuit fault interacts with other systems.

COMMON CAUSES ON HONDA ACCORD

• Faulty EVAP vent valve (solenoid) or its wiring: The valve that vents the EVAP canister may stay stuck, ground out, or fail to receive the proper signal.
• Vacuum/EVAP hose leaks or damaged fittings: Cracked hoses, loose clamps, or misrouted lines between the canister, vent valve, and intake can cause a vent circuit fault.
• Loose or faulty gas cap seal or missing cap: A common, low-cost cause of EVAP faults, including vent-related codes.
• Faulty EVAP canister or damaged purge/vent lines: Canister damage or leaks upstream/downstream of the vent valve can trigger errors.
• Electrical/connectors issues: Corroded, loose, or damaged wiring to the vent valve/ECU harness.
• Software or sensor interpretation anomaly: In rare cases, PCM software or a temporary sensor reading anomaly can trigger a pending code.
• Aftermarket modifications or added components in the EVAP path: Modifications can affect vent/purge valve operation or wiring integrity.

SYMPTOMS

• Check Engine Light (MIL) on or flashing.
• Typically no obvious loss of performance, but some drivers notice minor fuel economy changes.
• Possible vacuum/smell of fuel vapors if there is an EVAP leak in addition to vent-circuit faults.
• In some cases, no other symptoms; the car may run normally and the issue be primarily a diagnostic/valve circuit fault.

DIAGNOSTIC STEPS

Note: The steps below assume access to a standard OBD-II scanner and basic hand tools. If you’re not confident with electrical testing and EVAP systems, seek a professional.

Phase A — Confirm and scope

• Retrieve codes with a scan tool. Confirm P0446 is present and note any related codes (P0440, P0441, P0442, P0443, P0444, P0455, etc.). Record freeze-frame data and readiness monitors.
• Visual inspection first:
  • Check the gas cap: tighten until click, inspect gasket for cracks or wear, replace if questionable.
  • Inspect EVAP hoses and clamps for cracks, swelling, disconnections, or oil contamination around the canister area.
  • Look for signs of damage or misrouting around the EVAP canister, vent valve, and purge valve.
  • Check for signs of spilled fuel, residue, or vapor smell around the rear of the vehicle.

Phase B — Functional checks

• Verify vent valve operation (mechanical/electrical test):
  • With the ignition off and key out, locate the EVAP vent valve (often near the charcoal canister). Disconnect the electrical connector and inspect the pins for corrosion or damage.
  • Perform a basic continuity/coil resistance check if you have a multimeter and the factory spec. Compare to service manual values. If out of spec, replace the vent valve.
  • Reconnect and, with the ignition on (engine off), listen for a faint valve click when the ignition cycles or when commanded by the scanner. If no click, suspect valve or control circuits.
• Smoke test the EVAP system:
  • A smoke test is the most reliable way to find leaks anywhere in the EVAP path (hoses, canister, connections, vent valve). This will identify small leaks that may not be obvious visually.
• Electrical and wiring checks:
  • Inspect wiring harnesses and connectors to the vent valve and PCM for fraying, corrosion, or loose pins.
  • Check for vacuum/pressure signals while the engine is running to see if the vent valve is commanded to open/close correctly during EVAP purge cycles.
• Vacuum leak checks:
  • Use a vacuum gauge or hand-held leak detector to check for unexpected vacuum loss that could be traced to a vent valve or lines.
• If no leaks or valve faults found:
  • Consider testing the EVAP canister and purge valve (the purge valve can also influence EVAP circuits; a stuck purge valve could complicate interpretation of a P0446 in some vehicles).
  • Re-check for any related or pending codes after a short drive and monitor EVAP readiness.

Phase C — If faults are found and repaired

• Replace defective vent valve (solenoid) if confirmed faulty.
• Repair or replace damaged hoses, clamps, or fittings as needed.
• Replace gas cap if the cap seal is degraded.
• If a canister or purge valve is damaged, replace as indicated by findings.
• After repair, clear codes and perform a drive cycle (hundreds of miles) or rely on readiness monitors to confirm the fault does not return.
• If the code persists after repair and all obvious faults are eliminated, consult a technician for an ECU/PCM-related check or advanced EVAP diagnostics.

RELATED CODES

• EVAP family codes that commonly appear with or after P0446:
  • P0440 Evaporative Emission System Malfunction
  • P0441 Evaporative Emission System Incorrect Purge Flow
  • P0442 Evaporative Emission System Small Leak (0.04 inch)
  • P0443 Evaporative Emission System Purge Valve Circuit Malfunction
  • P0444 Evaporative Emission System Purge Valve Circuit Shorted
  • P0445 Evaporative Emission System Purge Valve Circuit Malfunction
  • P0446 (target code)
  • P0447 Evaporative Emission System Vent Control Circuit Malfunction
  • P0455 Large EVAP Leak
  • P0456 Very Small EVAP Leak
    Note: These related codes are commonly encountered in the EVAP family and may appear in conjunction with or as alternatives to P0446 during diagnostics.

REPAIR OPTIONS AND COSTS (2025 prices)

Prices are approximate ranges in USD and can vary by region, shop, and vehicle condition. They include parts and labor unless noted.

• Diagnostic fee (to identify P0446 and confirm EVAP cause)

  • Typical: $80–$150

• Gas cap replacement

  • Parts: $10–$30
  • Labor: $0–$50
  • Total: $10–$80

• EVAP vent valve replacement (primary fix for many P0446 cases)

  • Parts: $20–$150
  • Labor: $80–$200
  • Total: $100–$350

• EVAP purge valve replacement (if indicated or as a contributing issue)

  • Parts: $40–$180
  • Labor: $60–$180
  • Total: $100–$350

• EVAP canister (charcoal canister) replacement

  • Parts: $150–$300
  • Labor: $150–$350
  • Total: $300–$700

• EVAP system leak repair (hoses, clamps, connectors)

  • Parts: $5–$100
  • Labor: $60–$200
  • Total: $65–$300

• Canister line/hose replacement due to damage

  • Parts: $20–$100
  • Labor: $60–$180
  • Total: $80–$280

• Smoke test or advanced EVAP diagnostics (if not included in standard diagnostic)

  • Parts: minimal
  • Labor: $100–$200

• Electrical wiring repair to vent valve/ECU

  • Parts: $0–$50 (wiring length dependent)
  • Labor: $100–$300
  • Total: $100–$350

Notes

• Expect a broader cost if multiple components are affected, or if there’s a need to remove large components (fuel tank access) for inspection.
• In some markets, shops may waive diagnostic fees if you proceed with the repair; in others, the diagnostic fee is non-refundable if no repair is performed.
• Always verify the exact parts required for your specific Accord year and engine type (1.5L vs 2.0T) as configurations can affect vent valve geometry and canister layout.

DIY vs PROFESSIONAL

• DIY feasibility:
  • Gas cap replacement, visual inspection of hoses and clamps, and basic electrical checks are doable for a capable DIYer with a multimeter and basic hand tools.
  • A smoke test to definitively identify EVAP leaks is typically best left to a shop equipped with a smoke machine.
  • Replacing the EVAP vent valve or canister is feasible for experienced DIYers but note the risk of triggering emissions-related faults and the necessity of a proper check after repair (clear codes and ensure readiness).
• When to seek a professional:
  • If you don’t have ongoing access to a reliable smoke machine or you’re not confident in diagnosing EVAP circuits and electrical harnesses.
  • If the code persists after basic repairs, or if multiple EVAP components appear suspect.
  • If the vehicle is subject to emissions testing and you need a reliable repair that will pass inspection.

PREVENTION

• Inspect and secure the gas cap every time you fill up. Replace if worn or damaged.
• Regularly inspect EVAP hoses, lines, and clamps for cracks, wear, or loose connections, especially near heat sources or road debris.
• Avoid running the tank to extremely low levels too often; extended low fuel levels can stress EVAP components.
• Use good-quality fuel and avoid contaminants that might affect the EVAP system integrity.
• If performing any aftermarket fuel system work, ensure wiring and hoses don’t interfere with the EVAP lines or vent valve.
• If you notice a persistent smell of fuel, fuel economy drop, or a MIL on, address it promptly to prevent larger emissions-system issues.

Data limitations and transparency

• The provided dataset for 2018-2023 Honda Accord shows: No NHTSA owner complaints for this specific issue, and No recalls found in the NHTSA database.
• Because there are no complaints or recalls documented here, the guide relies on general EVAP knowledge and typical Honda Accord maintenance experience rather than statistically derived failure rates.
• Real-world failure frequency and cost data can vary by region, model year, engine variant, and maintenance history. Prices above are general estimates for 2025 and may differ in your area.

If you’d like, I can tailor this guide to your exact Accord model (trim, engine, VIN range) and walk you through a step-by-step diagnostic script with checks you can perform at home.