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Genchi Genbutsu
Genchi Genbutsu, Toyota Master Technician
Category: Toyota
Satisfied Customers: 4395
Experience:  Toyota Certified Master Diagnostic Technician, ASE Master Technician with L1 Advanced Engine
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My 2012 Toyota ghlander will sometimes make a noise like

Customer Question

Hi my 2012 Toyota Highlander will sometimes make a noise like something is running when the car has been sitting four hours turned off...any idea what this could be?
Submitted: 1 year ago.
Category: Toyota
Customer: replied 1 year ago.
Also what circuits remain energized while the ignition is off
Expert:  Genchi Genbutsu replied 1 year ago.

Thank you for allowing me to help you with this concern today and am sorry to hear that this is happening. I will have to ask you a few questions so that I can get a better understanding as to what may be going on with your Highlander.

All of the circuits will remain "energized" to some extent but if you were to conduct a parasitic load test, you would find that it was no more than 50 milliamps draw on the battery. The ECU's will slowly go to sleep and 50 mA is the max.

The noise you are hearing is most likely the EVAP system perfoming it's function check and giving it's monitor status to the engine ECU. They used to run this test using the LA4 drive cycle but that meant if a customer never drove the vehicle in this particular pattern, then the monitor would never run. The EPA made all manufactures switch over to an active test which will run all on its own. We hear customer complaints about this noise quite often.

Customer: replied 1 year ago.
Can you tell me where the pump is located?Thanks
Expert:  Genchi Genbutsu replied 1 year ago.

The pump is located near the rear of the vehicle but customers most often say that the hear the noise coming from the front not all though) because the EVAP system runs from the back of the vehicle through the gas tank and up to the engine. That is where the Purge valve is located which purges the gas vapors.

Does this make sense?

have you had a repair shop take a look at this concern for you?