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And a description of what happens during the ruckus of the Evaporation Leakage Checking Module's tests:
  • The evaporative emission control (EVAP) system in your Honda prevents fuel vapors from escaping into the atmosphere. The fuel vapors from the fuel tank are absorbed and stored by charcoal pellets in the charcoal canister.
  • The vent control valve is controlled by the engine control module (ECM) and allows air to flow into the charcoal canister to purge the gas vapors into the engine air intake to be burned.
  • The flow of the gas vapors from the charcoal canister to the engine air intake is controlled by a purge valve.
  • Both the vent control valve and the purge valve are usually open when the engine is at normal operating temperature; however, the ECM occasionally performs leak tests to ensure the evaporative emission control system is working properly.
  • During the leak test, the ECM closes the vent control valve and purge valve to create a vacuum.
  • If the EVAP system does not maintain the pressure, the ECM flags an evaporative emission control leak.
 
And a description of what happens during the ruckus of the Evaporation Leakage Checking Module's tests:
  • The evaporative emission control (EVAP) system in your Honda prevents fuel vapors from escaping into the atmosphere. The fuel vapors from the fuel tank are absorbed and stored by charcoal pellets in the charcoal canister.
  • The vent control valve is controlled by the engine control module (ECM) and allows air to flow into the charcoal canister to purge the gas vapors into the engine air intake to be burned.
  • The flow of the gas vapors from the charcoal canister to the engine air intake is controlled by a purge valve.
  • Both the vent control valve and the purge valve are usually open when the engine is at normal operating temperature; however, the ECM occasionally performs leak tests to ensure the evaporative emission control system is working properly.
  • During the leak test, the ECM closes the vent control valve and purge valve to create a vacuum.
  • If the EVAP system does not maintain the pressure, the ECM flags an evaporative emission control leak.
We could have just found our vibration issue...

If I remember correctly, fuel trims are fixed during close loop, and if the evaporations test happens during close loop, it could technically affect idle. When my truck had a clogged charcoal canister, during closed loop, it would have a "misfire" like idle, rougher than normal. Not saying that my truck is a direct comparison, but changing vacuum, or even the slight amount of fuel that gets burnt through the Evap. system, could be a suspect in our "vibration at idle" issue.

These tests under normal conditions (driving) would most likely be imperceptible to anyone (unless looking at engine data), but at idle, the engine can't transfer the vibrations through the tires, and instead is forced to transfer it through motor mounts.
 
We could have just found our vibration issue...

If I remember correctly, fuel trims are fixed during close loop, and if the evaporations test happens during close loop, it could technically affect idle. When my truck had a clogged charcoal canister, during closed loop, it would have a "misfire" like idle, rougher than normal. Not saying that my truck is a direct comparison, but changing vacuum, or even the slight amount of fuel that gets burnt through the Evap. system, could be a suspect in our "vibration at idle" issue.

These tests under normal conditions (driving) would most likely be imperceptible to anyone (unless looking at engine data), but at idle, the engine can't transfer the vibrations through the tires, and instead is forced to transfer it through motor mounts.
Do these type of leak checks happen while driving (in addition to the 15 minutes 5-10 hours after engine shutoff)? And would the explanation be related to cold engine temps, due to colder (less compressible) gas feed?
 
Do these type of leak checks happen while driving (in addition to the 15 minutes 5-10 hours after engine shutoff)? And would the explanation be related to cold engine temps, due to colder (less compressible) gas feed?
The system checks have to happen when the ICE is running, it's the only way to build vacuum without a dedicated pump. Colder gas evaporates less, in conjunction with oils having a higher viscosity when cold. One would suspect this test happens only when the vehicle is at operating temperature, but as colder weather sets in, the engine cools faster, and may not be within the optimal testing range.

This is a very rough theory, but it is does have some history with ICE vehicles, (evap system causing rough idle).
 
I think I finally heard the evap test sound for the first time tonight. I've had my Insight since 8/2018. It was exactly the same sound as the aforementioned Clarity video demonstrates. The car had been parked in the garage for 5.5 hours. I had just arrived back home in another car from my daughter's dance class. It wasn't difficult to miss in a quiet garage after the garage door closed. Even though I knew what it was, I was surprised since I had never heard it before. It's nice to know my Insight is taking care of itself.
 
I think I finally heard the evap test sound for the first time tonight. I've had my Insight since 8/2018. It was exactly the same sound as the aforementioned Clarity video demonstrates. The car had been parked in the garage for 5.5 hours. I had just arrived back home in another car from my daughter's dance class. It wasn't difficult to miss in a quiet garage after the garage door closed. Even though I knew what it was, I was surprised since I had never heard it before. It's nice to know my Insight is taking care of itself.
I experienced that sound(sounds like a loud hair trimmer :p) for the first time a few months ago. I heard it from my 2nd floor apartment and thought someone was running some sort of machine in the middle of the night. Looked out of the window and saw nothing except for the sound coming from my Insight.
 
Tonight I went to grab something out of the car and as I was about to leave I heard a humming sound. Traced it back to coming from underneath the car near the left rear wheel.
I'm assuming it's something to do with the HV battery, as when I remote started the car (unfortunately I didn't record that), it made a bunch of clicking (relay type) noises and then stopped before the engine kicked on.
But the sound was behind the rear axle, and more in the trunk. It wasn't very audible inside the car (ie, not coming from underneath the rear seats where the HV battery is as far as I understand). I've posted a video below. On another recording, I move my phone from the rear bumper to the axle, and the sound is loudest 3/4 of the way towards the rear wheel axle.

Anyone know what this is? Is this normal? (Could be, I don't generally sit out there and listen to the car)

 
Tonight I went to grab something out of the car and as I was about to leave I heard a humming sound. Traced it back to coming from underneath the car near the left rear wheel.
I'm assuming it's something to do with the HV battery, as when I remote started the car (unfortunately I didn't record that), it made a bunch of clicking (relay type) noises and then stopped before the engine kicked on.
The video humming and location sounds like the vacuum pump inside the fuel evaporation leak check module, similar to the Clarity video example in post #20. It's not related to the HV battery, but moreso the fuel area (which is located behind th HV battery). The pump is known to run for 15 minutes after the engine has been shut down for 5-10 hours.

Separate from the evaporation leak check module, I think the clicking noises during remote start might be the electrical relay checks/interlocks (?). Have you used remote start before, or is the first time you've used and observed?
 
I just heard the same exact sound in my 2019 insight. Im hoping it's the fuel evap test I've read about in other vehicles, but some confirmation would be nice.
I heard the same sound for the first time yesterday. I found this thread and decided to try popping open the gas door. It immediately stopped and I figure that's a decent confirmation.
 
Thread bump!:D
Wow, I just heard the same noise tonight and was a bit concerned. Had to check AllData first to see what was located back there, then googling led me here!
Good to see that it is normal! 2022 Insight Touring
 
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