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Discussion Starter #1 (Edited)
Can anyone help me figure this out? I assume this noise is from the Voltec unit. (Louder on the driver's side.) I already checked, it's not the radiator cooling fans. Raising the hood starts the engine, so I stuck my smartphone under the the engine to record the sound. At first, when the car was in the driveway, I thought I heard a cricket under the hood. Then, in the quiet of the garage, it was more discernible. Noise is only present in Park and Neutral. No sound at all in R, D and L (with parking brake firmly engaged!) Makes the sound even when plugged in (though I can't move the shifter out of P when plugged in.)

I''d appreciate hearing from others (pun intended) as to whether they have the same noise.

You'll need to turn up the speaker volume to hear it. Sorry, it's just a smartphone recording. I recorded the sound in both P and N -- essentially the same noise. Chirping, possibly rotational noise. Fans inside the inverter box? Noise is present both in the morning (before first drive of the day) or also otherwise, when the car is hot.

http://mama.indstate.edu/users/chat/InPark.m4v
http://mama.indstate.edu/users/chat/InNeutral.m4v

Thanks!

2014-05-23 UPDATE: It DOES make the noise in R, D & L. Sorry. I guess I just wasn't hearing it as loudly. -b
 

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Can anyone help me figure this out? I assume this noise is from the Voltec unit. (Louder on the driver's side.) I already checked, it's not the radiator cooling fans. Raising the hood starts the engine, so I stuck my smartphone under the the engine to record the sound. At first, when the car was in the driveway, I thought I heard a cricket under the hood. Then, in the quiet of the garage, it was more discernible. Noise is only present in Park and Neutral. No sound at all in R, D and L (with parking brake firmly engaged!) Makes the sound even when plugged in (though I can't move the shifter out of P when plugged in.)

I''d appreciate hearing from others (pun intended) as to whether they have the same noise.

You'll need to turn up the speaker volume to hear it. Sorry, it's just a smartphone recording. I recorded the sound in both P and N -- essentially the same noise. Chirping, possibly rotational noise. Fans inside the inverter box? Noise is present both in the morning (before first drive of the day) or also otherwise, when the car is hot.

http://mama.indstate.edu/users/chat/InPark.m4v
http://mama.indstate.edu/users/chat/InNeutral.m4v

Thanks!
Is that Morse code for S O S? (Sorry 8^)

It does sound repetitive.
 

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It sounds like to me the electric oil pump that's in the power drive unit/transmission. However this pump normally doesn't run while in N or P. In my Volt I hear the pump briefly running the moment I move the gear selector into D or R. It needs to run the electric pump to generate hydronic pressure for the clutch(s) because neither the engine or traction motor is running. Once the Volt is in motion I think it uses a mechanical pump to maintain oil pressure. Maybe the electronics in your Volt is getting confused and running the pump when it's not supposed to.
 

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Discussion Starter #4
Thanks Eric99. I see (heard) what you are saying. This is different though. I'm guessing it's there all the time -- only I can't hear it while I'm driving. I hear it while I start rolling from a stop. Not sure if the pitch of the noise changes with speed -- too faint to hear it over road noise. Weird. I'll rig up a stethoscope, maybe. Hope no one sees me, or they'll think I'm fit for the funny farm..
 

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There is a pipe clamp that is close to the driver's wheel well that can rub against it or the frame when there is vibration. Do you also here it when you close the door firmly? Only a few squeeks in this scenario.
 

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Discussion Starter #6
Happens all the time even when the car isn't moving.

Does anyone know if there are cooling fans inside the Voltec electrical (inverter, etc.) module? Sounds like a squeaky fan or something in there.
 

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Happens all the time even when the car isn't moving.

Does anyone know if there are cooling fans inside the Voltec electrical (inverter, etc.) module? Sounds like a squeaky fan or something in there.
If it happens all the time it should be easy for a Chevy tech to find, diagnose and fix if needed. Take it to your dealer for servicing. Take your recording as well. Have them verify they can hear the sound when you drop it off.
 

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From the audio files it sounds like the normal high frequency "ringing" noises from the Transmission Control Module (TCM) to me.
(all GMs with newer 6-speeds do it and the Voltec uses the same TCM)

To confirm you may find the sound is still present for about 10-20 seconds after you shut OFF the car then stops.
It shouldn't be audible from the cabin although sometimes I can notice this TCM noise with the windows down while inside a garage or driving close to a structure.

In any case it doesn't sound like anything serious but if you take it to a dealer they can confirm that.

WOT
 

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Discussion Starter #9
--
From the audio files it sounds like the normal high frequency "ringing" noises from the Transmission Control Module (TCM) to me. (All GMs with newer 6-speeds do it and the Voltec uses the same TCM)

To confirm you may find the sound is still present for about 10-20 seconds after you shut OFF the car then stops.
It shouldn't be audible from the cabin although sometimes I can notice this TCM noise with the windows down while inside a garage or driving close to a structure.
--

Thanks Wopontour and Steverino. The noise goes away as soon as the car is turned off. (Doesn't persist after shutdown.) Comes back on as soon as the car is turned on (even when plugged in.) It's not temperature sensitive, though I don't quite recall it being there when it was really cold here in the Midwest about three months ago. It's audible in the garage and, if you listen closely, in the driveway. Though I will say I'm hearing an new electric motor noise in the back now that Summer has come (I assume a liquid circulation pump.) Road noise drowns this one out, but I can hear it (the new noise) while backing out the driveway.

I'll have the dealer look at it and listen to the noise and the recording. It's quite tolerable at the moment and I won't have them fool with it unless it gets much louder. I bought this Volt used, four months ago, and I'm REALLY liking it, despite its quirks. So I don't want unnecessary surgery performed on it (especially if it might lead to other issues) since the dealers around here don't see many Volts and are unfamiliar with them -- they seem to approach them with a curious mix of fascination and disdain!

2013 Topaz Premium 23,900 mi
 

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Hi All
I hear mine when I do auto start sounds more like R2D2 from Star Wars LoL.

Thanks
Don
 
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