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2016 Q70 Check Engine Light P0455 - Large EVAP Leak

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David L. · rep 0 · May 25, 3:46 AM · 1 replies · solved · Question

Vehicle: 2016 Infiniti Q70 3.7L

My 2016 Infiniti Q70 3.7L has had its check engine light on for a few days now. I scanned it and got a P0455 code, which indicates a 'Evaporative Emission System Leak Detected (Large Leak)'.

I've already checked the gas cap, tightened it, and even tried replacing it with a new one, but the light came back on. The car drives perfectly fine, no performance issues or anything, just that annoying light.

What are the typical causes for a large EVAP leak on a Q70? Are there other common places to check besides the gas cap? I'd like to try and narrow it down before I have to take it in for a smoke test.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:46 AM

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ClearTheCode admin answer:

The P0455 code on your 2016 Infiniti Q70 indicates a large leak in the Evaporative Emission (EVAP) system. This system is designed to prevent fuel vapors from escaping into the atmosphere. While often benign in terms of driveability, it's an emissions failure and needs to be addressed.

Here are the most common causes for a P0455 code, beyond the gas cap:

  1. Loose or Damaged Hoses: The EVAP system consists of many rubber and plastic hoses that run from the fuel tank to the engine. Over time, these hoses can become brittle, crack, or disconnect. Carefully inspect all visible EVAP lines for any signs of damage, especially around the fuel tank, charcoal canister, and purge valve.
  2. EVAP Canister: The charcoal canister stores fuel vapors. It can develop cracks or leaks, especially if located in an area prone to road debris. Its vent valve can also stick open.
  3. Purge Valve (Canister Purge Solenoid): This valve controls the flow of fuel vapors from the charcoal canister to the engine's intake manifold. If it's stuck open, it can create a large vacuum leak, triggering the P0455 code. You can often hear it clicking if it's working, or try to blow through it when it's closed (it should be sealed).
  4. Vent Valve (Canister Vent Solenoid): This valve opens to allow fresh air into the EVAP system when the purge valve is open. If it's stuck open, it can mimic a large leak. This valve is usually located near the charcoal canister.
  5. Fuel Tank Pressure Sensor: While less common for a 'large leak' code, a faulty fuel tank pressure sensor could potentially report incorrect pressure readings, leading the ECM to incorrectly detect a leak.

Diagnosis Steps:

  • Visual Inspection: Start by visually inspecting all accessible EVAP hoses and components under the vehicle, especially around the fuel tank and under the hood where the purge valve is located.
  • Listen for Hissing: With the engine off and the fuel cap removed, sometimes you can hear a faint hiss if there's a significant leak in a hose.

When to See a Shop: If a thorough visual inspection doesn't reveal any obvious hose damage or a faulty gas cap, it's highly recommended to take your Q70 to a professional mechanic. They have specialized equipment, such as a smoke machine, which injects smoke into the EVAP system. The smoke will escape from any leak points, making them easy to identify. This is the most effective way to pinpoint the exact location of a large EVAP leak.

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