High pitched ring sound with engine off!?

[DSN46]

So... I noticed the other day that when I turn the key to the "ACC" position, there is a very high-pitched, electronic-type ringing noise coming from the transmission area underneath. You can't hear it from inside the cab... only if you step outside. What in the world could be making such a sound? I narrowed it down to the transmission area... almost sounds like it is coming from inside the transmission. The engine is off.

Anybody have a clue?

Thank you!

2010 Tahoe LT

 

[Doubeleive]

are you sure it's not your fuel pump? try pulling the fuel pump fuse and see if you still hear the same sound.

 

[DSN46]

I'm 100% sure. It's coming from the transmission area. I just replaced the fuel pump and know what they sound like. Thanks!

 

[DSN46]

So did some more messing around with it today. When I pulled the underhood fuse #19 which is the transmission control fuse, the noise stopped. It HAS to be coming from the transmission... but WHAT inside the transmission would give off a high pitched squeal with only the key on but not started?

Anyone?

 

[Doubeleive]

no clue, but I'm gonna sub to this one to find out, any idea's @swathdiver @sumo

 

[swathdiver]

So did some more messing around with it today. When I pulled the underhood fuse #19 which is the transmission control fuse, the noise stopped. It HAS to be coming from the transmission... but WHAT inside the transmission would give off a high pitched squeal with only the key on but not started?

Anyone?

no clue, but I'm gonna sub to this one to find out, any idea's @swathdiver @sumo

I can't say exactly but inside the transmission resides the TCM which has the solenoids and pistons and something is amiss in there. Do you know someone with a Tech2 or bi-directional scan tool that can test them? You don't have a Hybrid do you? That transmission has two 60 KW electric motors.

 

[DSN46]

Thanks guys! I guess I'm going to have to run down the dealer and have them hook it up. I DID find a TSB PIP4021B that refers to a high pitched whine coming from the transmission and it says it is the TCM calling for the solenoids to build up pressure and that it is a "normal" operation... BUT it says it should be doing it for only a period of about one minute... mine will go as long as I let it. Thanks again. I will let you know what I find out.