# Engine Bay High Pitch Frequency Sound "CLASSIFIED SECRET"



## OnlyTaurus (Mar 20, 2012)

Interesting. Are you sure it's the transmission? I too have had that high pitch electrical noise, but my transmission's a manual.

Kinda weird they won't say anything.


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## obermd (Mar 3, 2012)

The MTs also have the Transmission Control Module - it's just programmed differently.


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## Aussie (Sep 16, 2012)

"Classified" usually means "I don't know", or if military "I don't want you to know".


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## obermd (Mar 3, 2012)

Don't forget the government's other definition of "classified" - "I'm embarrassed to let anyone know I'm such an idiot."


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## rmass09 (Apr 17, 2011)

It must be like stickers and be a secret thing to add HP! Clown horns here I come!


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## OnlyTaurus (Mar 20, 2012)

obermd said:


> The MTs also have the Transmission Control Module - it's just programmed differently.


Are you sure? There is no listing of a module in Service Information.. nor have a seen one.


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## obermd (Mar 3, 2012)

OK - I may be wrong. What's controlling the red-line engine limiter then?


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## jblackburn (Apr 14, 2012)

The ECU controls everything in a MT car. There's no transmission computer on a manual car.

The ECU is usually programmed differently for a MT car. You will notice that the Cruze has a "rev hang" when you shift, and bumps up RPMs when you let the clutch out in neutral. The MT Cruze also hits full boost at 2500 RPM rather than the 1850 RPM AT's do.

My theory is that it's the expansion valve in the AC system. They are known to "squeal" at times.


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## Aussie SRi-V (Aug 25, 2012)

Good theory, and it could be the case with a gas bypass type of sound.
However, after locating it within the transmission outer black plastic cover, I'm sure its not the AC system.
That is, unless my tranny oil is cooled by heat exchangers and a very classified AC cooling system.


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## Aussie SRi-V (Aug 25, 2012)

*Transmission Control Module*
A 32-bit transmission controlmodule (TCM) monitors transmission performance and compensates for normal wearin components such as clutch plates, so transmission performance remainsconsistent for the life of the transmission. The control module also “tests”the components of the transmission following assembly to optimize theinteraction of the components. 

The TCM is mounted inside thetransmission, where temperatures remain mostly constant compared to an external-mountedmodule. It is small in size, which helps minimize the overall size of thetransmission. The transmission and module are assembled together, so noadditional connections are necessary during vehicle assembly. 

*TECHM*The 6T40/6T45’stransmission electronic hydraulic control module (TEHCM – pronounced “TECH-im”by engineers) contains basic software and algorithms shared among allHydra-Matic six-speed variants, including RWD, FWD and AWD. The module islocated inside the transmission, which reduces manufacturing complexity, andrequires only vehicle-specification calibration to the core program. The TECHMalso enables features such manual shift control and grade logic.


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## jblackburn (Apr 14, 2012)

> That is, unless my tranny oil is cooled by heat exchangers and a very classified AC cooling system.


GASP! You discovered their secret!!! 

Quick, run and hide before the black Suburbans show up...


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## OnlyTaurus (Mar 20, 2012)

jblackburn said:


> GASP! You discovered their secret!!!
> 
> Quick, run and hide before the black Suburbans show up...


:lol::signs015:


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## dwilson (May 11, 2014)

Im no expert but a high pitch sound while driving may be the turbo?


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## Aussie (Sep 16, 2012)

Can somebody explain to me why, when the noise has stopped after the engine has been off for a minute or so, the noise starts again if I lock or unlock the doors with my remote?


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## Merc6 (Jun 8, 2013)

The sound is cooling, yet I hear it while car is on idling inside a parking garage.


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## BradSt (May 2, 2013)

I haven't heard this sound since last summer. Just heard it again last night, when I shut the car off in the garage. If you key the car back on, and off, it is gone. It sounds like an energized solenoid or transformer to me. Some cheap HID kits I've had in the past, made similar noises. It is definitely electrical.


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## AutumnCruzeRS (Sep 10, 2012)

When opening the hood Ive had heard this noise. Sounds to me like a purge of some sort.


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