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2018 Outlander P0455 Code - EVAP Gross Leak - What to Check?

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Chris P. · rep 0 · May 22, 5:31 AM · 1 replies · solved · Question

Vehicle: 2018 Mitsubishi Outlander SEL

Hey everyone,

My check engine light just came on in my 2018 Mitsubishi Outlander SEL, and I pulled the code P0455. It indicates an EVAP system gross leak.

I've already tried tightening my gas cap, but the light hasn't gone off yet after a couple of drive cycles. I'm wondering what are the most common culprits for this code on these Outlanders?

Are there any specific hoses or valves I should be looking at first? Any DIY checks I can perform before taking it to a shop? Thanks for any advice!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:31 AM

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ClearTheCode admin answer:

The P0455 code (EVAP System Gross Leak Detected) on your 2018 Mitsubishi Outlander SEL is a common issue, often related to the evaporative emissions system. This system prevents fuel vapors from escaping into the atmosphere.

Here are the common causes and diagnostic steps:

  1. Loose or Faulty Gas Cap: While you've tightened it, sometimes the cap itself can be faulty and not seal properly. Consider replacing it with an OEM cap if the light persists.
  2. EVAP Hoses: Inspect all vacuum and EVAP hoses for cracks, disconnections, or damage, especially those leading to and from the purge valve, vent valve, and charcoal canister. Rodent damage is also a possibility.
  3. EVAP Purge Valve: Located near the engine, this valve controls the flow of fuel vapors from the charcoal canister to the engine. If it's stuck open, it can cause a gross leak. You can often test it with a vacuum pump or by listening for a click when 12V is applied (if accessible and safe to do so).
  4. EVAP Vent Valve (Canister Vent Solenoid): Usually located near the charcoal canister (often under the vehicle near the fuel tank), this valve opens to allow fresh air into the system during the purge cycle. If it's stuck open or faulty, it can also cause a gross leak.
  5. Charcoal Canister: Less common, but the canister itself can crack or be damaged, leading to a leak.

When to See a Shop: If after checking the gas cap and visually inspecting hoses you can't find the source of the leak, it's best to take your Outlander to a qualified mechanic. They have specialized smoke machines that can inject smoke into the EVAP system, making even tiny leaks visible. They can also perform more advanced diagnostic tests on the purge and vent valves to pinpoint the exact faulty component. Driving with an EVAP leak won't typically cause immediate driveability issues, but it will prevent your vehicle from passing emissions tests and contributes to air pollution.

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