nother toyota corolla question...sound in back while shut off

[Sigene]

2008 corolla

It had been sitting in my garage for 6 hours. I went out to throw some trash away and noticed a slight humming sound coming from the driver's side rear. It sounded a little like a motor or a pump. After a couple of minutes it shut off.

What made the sound? why did it kick on even after the car had been shut off for 6 hours? Is it supposed to do that? How often would I expect this thing to happen?

(The only thing I can guess that's back there is the fuel pump, but I don't know why it would kick on spontaneously)

[Uncommon Sense]

2008 corolla

It had been sitting in my garage for 6 hours. I went out to throw some trash away and noticed a slight humming sound coming from the driver's side rear. It sounded a little like a motor or a pump. After a couple of minutes it shut off.

What made the sound? why did it kick on even after the car had been shut off for 6 hours? Is it supposed to do that? How often would I expect this thing to happen?

(The only thing I can guess that's back there is the fuel pump, but I don't know why it would kick on spontaneously)

Is it possible that your keys are still in the ignition? Maybe the car isn't as "off" as you think....
The other possibility is that there is a motion sensor on this car. Doubtful.

[Enola Straight]

As a valet driver, I have noticed that certain upscale cars like Cadillac and Lincoln have pneumatic suspension components which maintain a level ride...often activating at apparently random intervals, after the car has been shut off.

Perhaps your car has something similar?

[Omegaman]

I would check your owners manual first. Probably a waste of time though. I can't think of any pump or motor that should come on while the vehicle is off. A call to one of the service advisors at your dealer might be a good idea. If it something normal they would most likely be aware of it and if they don't have a clue I would take it to the dealer and let them figure it out.

Be cautioned it may take them a while to figure it out as they will have to duplicate the condition.

[Myglaren]

As a valet driver, I have noticed that certain upscale cars like Cadillac and Lincoln have pneumatic suspension components which maintain a level ride...often activating at apparently random intervals, after the car has been shut off.

Perhaps your car has something similar?

My first thought as my car has hydropneumatic suspension and on unlocking it whirrs and levels itself.
If left long enough unlocked it will `dance' especially on uneven ground, until it goes into economy mode and shuts off everything electrical to prevent draining the battery.

The other thing is the lift pump in the tank, but that only ever activates when the ignition is on, before the engine starts, to prime the system.

[Fubaya]

There are posts here (http://www.toyotanation.com/forum/showthread.php?t=251607) where people say new corollas have a sticker around the shifter that states the noise is from a routine check performed 5 hours after shut off. None of the people seem to remember exactly what is running, but I bet that's the ballpark answer.

[Really Not All That Bright]

The wifey has a 2007 Corolla that does exactly the same thing. Scared the hell out of me when I was smoking a cigarette while leaning on the trunk at around 2 a.m.

[Sigene]

There are posts here (http://www.toyotanation.com/forum/showthread.php?t=251607) where people say new corollas have a sticker around the shifter that states the noise is from a routine check performed 5 hours after shut off. None of the people seem to remember exactly what is running, but I bet that's the ballpark answer.

As for the notice, it was a tag on the gear knob that said a noise may appear below the luggage compartment approximately 5 hours after the car is shut off. The car is performing an evaporation test and it is the motor that you are hearing. i still have the tag, anal like everyone else here i guess :-), if you really want the wording down.

Yikes; that's almost certainly it; but I haven't found anything else on the web that would confirm it.

T' Dope is most excellent in tapping into the collective knowledge base

[Joey P]

There are posts here (http://www.toyotanation.com/forum/showthread.php?t=251607) where people say new corollas have a sticker around the shifter that states the noise is from a routine check performed 5 hours after shut off. None of the people seem to remember exactly what is running, but I bet that's the ballpark answer.

If that's not it, my next guess would be that your fuel pump is running due to a faulty relay.

[control-z]

My 2008 Mazdaspeed 3 does the same sort of thing. I asked on a Mazda forum and got the following answer:

What you are hearing is an air pump. It's the ECU checking the evaporative emissions system for leaks. The ECU will wait for several hours after the engine is turned off before running this test. If the ECU detected a problem, the CEL would be lit the next time you started the car.

[Rick]

control-z nailed it. Federal regulations require the engine management system to check the the fuel system for vapor leaks as small as 0.5mm.
Over the years there have been various strategies for doing this.
One very popular one is to use a pump after the engine has been off for a period of time. When the test starts, the pump fires up and pushes air though a 0.5mm calibrated hole. The ECU records the amount of current necessary to push air though this hole. This is called the reference phase. The the system switches and starts to pump air into the tank. As the tank pressurizes the current draw of the pump increases. When the pump current exceeds what the current draw was during the reference phase, the system knows that there is no hole exceeding 0.5mm in the system.
Pretty simple and very reliable.

Also some cars will turn on the heater fan on high for 5 minutes or so after the car has been parked for a while, to dry the evaporator out and prevent mold, mildew, and smells.

[control-z]

And to further clarify, ECU is a fancy acronym for a computer that controls one or more systems in a car. Not unlike your PC or cell phone really.

[Rick]

And to further clarify, ECU is a fancy acronym for a computer that controls one or more systems in a car. Not unlike your PC or cell phone really.:smack:

Engine Control Unit
or
Engine Control Module

ECU, ECM interchangeable terms actually.