delco stereo scv problem, HELP!!!

[briansease]

i have a 97 tahoe with an acdelco stereo. it is equipped with scv (speed controled volume). this has to be the lamest thing ever invented. the problem is that it turns my stereo down whenever it feels in the mood, and when i try to turn it back up it cranks it all the way up. is this feature wired to something like the speedo or brake pedal? if so, can i just cut the wire and what color wire is it? any help would be appreciated. thanx

[Jeremy-WI]

dark green with a white stripe, if you cut it tape it up good or it might mess with the PCM, it still may but I've never needed to cut it

[Jeremy-WI]

or you could turn the scv knob all the way counterclockwise, should disable scv

[briansease]

Originally Posted by Jeremy-WI

dark green with a white stripe, if you cut it tape it up good or it might mess with the PCM, it still may but I've never needed to cut it

what is PCM?

[briansease]

Originally Posted by Jeremy-WI

or you could turn the scv knob all the way counterclockwise, should disable scv

i have tried this and it does not turn the scv off.

[Jeremy-WI]

powertrain control module. If you tape the wire up so it can't ground out, it shouldn't be a problem.

[briansease]

Originally Posted by Jeremy-WI

powertrain control module. If you tape the wire up so it can't ground out, it shouldn't be a problem.

my wife has been driving more than me latley, she says that the truck didn't want to shift out of first the other day. then the stereo problem started. i had the stereo problem all last summer and now it has returned. i live in denver, could the change in the weather (cold-hot) have somthing to do with this problem? is the shifting (very intermitant, once in a blue moon) and the stereo related? could my powertrain control module be going out? i appreciate your help, you must be a chevy mechanic or an avid Tahoe fan. i love mine, 2dr, will be a classic some day since they don't make 2dr anymore.

[Jeremy-WI]

I don't think its your PCM going bad, possibly wiring or a connector at your transmission, but could be the vehicle speed sensor going bad. Check the wiring going to it, unplug the connector and apply some dielectric grease to the pins. The speed sensor is on the drivers side of trnsmission and a bit back farther than the oil pan goes, on the extension housing or tailshaft

[briansease]

Originally Posted by Jeremy-WI

I don't think its your PCM going bad, possibly wiring or a connector at your transmission, but could be the vehicle speed sensor going bad. Check the wiring going to it, unplug the connector and apply some dielectric grease to the pins. The speed sensor is on the drivers side of trnsmission and a bit back farther than the oil pan goes, on the extension housing or tailshaft

i did have the transmission serviced (full service) and beleive they removed it. could the dealer have created this problem on accident? i do believe they removed the transmission for this full service to do spec on it due to a dnyo tester that left my ebrake on and fryed my diff. seals. i thought that maybe there was some transmission wear done when the tester left my brake on and the dealer did a full inspestion of the transmission.

[typicalsituations]

Hmmm.. if turning the SCV ring all the way down to the bottom didn't stop that problem, I would think your radio may be busted. That is supposed to disable that feature. It does in my tahoe.

[350chevy]

I think I have same problem in 96 Tahoe. The bizarre thing is, sometimes the radio will blare if you lean on the armrest while reaching in the back seat. There is a box under the driver seat, but I don't know if it is related to the radio or just part of the seat control.
Sometimes the volume goes to zero, and if I screw with it it goes full blast.

[smokey1102]

I dont know if this is related but on my 88 C/K the radio/clock/ tape player all quit at the same time the fuse is ok. is there a control box that operates these assesories?

[p0peye_34]

I appologize for bringing such an old thread back to life, but it didn't look as though this one was answered.

Anyway, I've been searching the threads for a similar problem with my '96 GMC Sierra, and when I ran across this one, a bolt of lightening struck me.

Originally Posted by briansease

i did have the transmission serviced (full service) and beleive they removed it. could the dealer have created this problem on accident?...

I had just replaced the clutch, and got everything back together. Pulled it out of the garage and test drove it for a while, then turned the radio on. Volume was up and down so bad that it blasted my ears one second and was "off" the next.

I wasn't thinking coincendence here, since I didn't go anywhere near the radio during the clutch swap, so I was about to purchase a used radio, thinking that it was done.

After reading this, I couldn't believe that someone else had the same issue after having transmission work done, so I did some of my own research.

It seems that the speed control sensor is tied to the radio's SCV.

The first thing that occured to me was that when the transfer case was out, I had pressure washed the beast, along with everything else. The bag that I taped to the speed control sensor let loose and went flying, but that didn't stop me from blasting the thing with 2200 lbs of water pressure!

I thought I had dried everything off well enough before putting it all back together, but apparently, the SCS must have held some water in it.

After my incident, I pulled the wire connector off and blasted the SCS with compressed air. Plugged it back in, and all is right with the radio now!

My advice, before you incur expensive dealer visits or an unnecessary radio replacement, is to check the connector for the SCS and the wires leading up to it.

TR

[p0peye_34]

I thought I'd update all on the situation.

The "cleaning" of the connector worked for about two days.

Then it was back to the same old too loud, can't hear it.

Funny thing was that when I turned the steering wheel to the right, the volume went down. Straight or left brought the volume back.

The wife thought I was completely nuts when I mentioned it to her, but I looked at the wiring diagram for the PCM, and it has the the speed sensor and the steering sensor both connecting to that green/white wire leading to the radio.

I thought I was smarter than the PCM and connected an aftermarket radio to the harness that didn't have the green/white wire - but the problem got worse. No sound at all!

So, I took the advice of the pros, and cut the green/white wire, taped it back, and plugged up the original radio.

I'll let you know later if it worked, but it sounds great sitting in the 17 degree garage right now.

TR