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2021 Highlander XLE - P0455 EVAP System Leak (Large)

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Mike T. · rep 0 · May 25, 1:24 AM · 1 replies · solved · Question

Vehicle: 2021 Toyota Highlander XLE

Hey everyone,

My 2021 Toyota Highlander XLE, with about 28,000 miles, just got a Check Engine Light. I scanned it with my OBD-II reader, and it's showing a P0455 code: 'EVAP System Leak Detected (Large Leak)'.

I've already checked the gas cap, made sure it was tight, and even removed and re-tightened it a few times. I cleared the code, but it came back after a couple of drive cycles. I haven't noticed any performance issues or strange smells, just the persistent light.

What are the common culprits for a P0455 on these newer Highlanders? Is there anything else I can easily check before taking it to the dealership? Thanks in advance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 1:24 AM

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ClearTheCode admin answer:

A P0455 code, indicating a 'Large Leak Detected' in the Evaporative Emission Control (EVAP) system, is a common issue. While you've correctly checked the gas cap, there are several other potential sources for such a leak, even on a relatively new 2021 Toyota Highlander.

The EVAP system is designed to prevent fuel vapors from escaping into the atmosphere. It's a closed system, and any breach can trigger this code.

Here are the most common causes for a P0455 code:

  1. Loose or Faulty Gas Cap: (You've checked this, but sometimes the cap itself can fail to seal properly even if tightened).
  2. EVAP Purge Valve: This valve controls the flow of fuel vapors from the charcoal canister to the engine's intake manifold. If it's stuck open or leaking, it can cause a large leak. You might hear a clicking sound from it when the engine is running.
  3. EVAP Vent Valve (Canister Vent Valve): This valve controls fresh air entering the charcoal canister. If it's stuck open or faulty, it can prevent the system from sealing during a leak test.
  4. Cracked or Disconnected EVAP Hoses/Lines: Over time, or due to rodent damage, the rubber or plastic hoses that carry fuel vapor can crack, become brittle, or simply disconnect. These hoses run from the fuel tank to the charcoal canister and to the purge valve.
  5. Charcoal Canister Damage: The charcoal canister itself can sometimes crack or be damaged, leading to a leak. This is less common but possible.

When to see a shop:

  • If after visually inspecting accessible hoses for cracks or disconnections, and ensuring the gas cap is fully functional, the code persists.
  • Diagnosing EVAP leaks often requires specialized equipment, such as a smoke machine, to visually locate the exact source of the leak. A professional shop can perform this test efficiently.
  • Replacing EVAP components like the purge valve, vent valve, or canister can be complex, involving hard-to-reach areas and specific procedures. If you're not comfortable with these repairs, a certified technician is your best bet.
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