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P0455 Code on 2021 Highlander XLE - Large EVAP Leak

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Nicole W. · rep 0 · May 22, 2:15 AM · 1 replies · solved · Question

Vehicle: 2021 Toyota Highlander XLE

Hello ClearTheCode community,

I'm getting a Check Engine Light on my 2021 Toyota Highlander XLE, and the code is P0455: 'EVAP System Leak Detected (Large Leak)'. I've already checked the gas cap, tightened it until it clicked several times, and even removed and re-seated it, but the light came back on after a few drive cycles.

The car runs perfectly fine, no performance issues or strange smells. I'm hoping it's something relatively simple and not a major component failure in the EVAP system. It only has about 45,000 miles on it.

What are the most common causes for a P0455 on a newer Highlander? Is there anything else I can easily check myself before taking it to a mechanic? Any advice would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 2:15 AM

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ClearTheCode admin answer:

The P0455 code on your 2021 Toyota Highlander XLE indicates a 'Large Leak' in the Evaporative Emission Control (EVAP) system. This system is designed to prevent fuel vapors from escaping into the atmosphere. While the car may run fine, this code will prevent you from passing an emissions test.

Since you've already checked and re-tightened your gas cap, which is the most common cause, here are other potential culprits for a large EVAP leak:

  1. Loose or Damaged Hoses/Lines: The EVAP system consists of many rubber and plastic hoses and lines that connect various components. Over time, these can become cracked, brittle, or simply come loose, creating a large leak. Visually inspect all accessible EVAP lines, especially those near the fuel tank, charcoal canister, and engine bay.
  2. Charcoal Canister: The charcoal canister stores fuel vapors. It has vent valves and purge valves. A crack in the canister itself or a fault with its vent valve (often called the Canister Vent Valve or EVAP Vent Solenoid) can cause a large leak. The vent valve is typically open when the engine is off and closed during a leak test.
  3. Purge Valve/Solenoid: The EVAP purge valve controls the flow of fuel vapors from the charcoal canister to the engine's intake manifold to be burned. If this valve is stuck open, it can create a large vacuum leak, which the system might interpret as a large EVAP leak. You can sometimes test this by listening for a click or checking its resistance with a multimeter.
  4. Fuel Tank Pressure Sensor: While less common for a 'large leak' specifically, a faulty fuel tank pressure sensor could provide incorrect readings to the ECU, leading to an erroneous P0455 code.
  5. Fuel Filler Neck: Damage or corrosion to the fuel filler neck where the gas cap seals can also prevent a proper seal, mimicking a loose gas cap.

When to see a shop:

  • If a thorough visual inspection of hoses and the gas cap area doesn't reveal any obvious issues.
  • Diagnosing EVAP leaks often requires specialized equipment, such as a smoke machine, to visually locate the leak points in the system. This is beyond typical DIY tools.
  • If you suspect a faulty purge valve or vent valve, as these components can be tricky to test accurately without proper diagnostic procedures.
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