unique cruise problem

[Gemmell]

Hey everybody, I've got a 95 Tahoe with an odd cruise problem that I can't find any information on. Hopefully someone can give me a suggestion.

Cruise doesn't work at all. Multifunction and brake switches check out fine but the signal from the pcm didn't. The computer doesn't appear to be sending the right signal to the cruise module. The speedometer works fine though.
It is also worth mentioning that I cannot communicate with the obd 1 port with a scan tool. Although jumping the diagnostic terminal will tell me that it has no stored codes. The truck also does the voltmeter dance when the blinkers or accessories are turned on. Bad ground somewhere, maybe a potential cause.

Just wondering if there's something I've missed (different speed sensor). I'm leaning towards a bad pcm, which I find odd because they are usually bullet proof.

Any help would be most appreciated! Thanks in advance

 

[SunlitComet]

bad grounds or wiring for the dancing. are you saying the module is not receiving the speed signal from the vss?

 

[Gemmell]

It's receiving something but the voltages were lower than expected according to the troubleshooting specs I found.

I assumed the vss must be working since the speedometer works. Unless that runs off a different sensor?

 

[SunlitComet]

what voltages tested on what wires? if the speedo works then the speed sensor could be giving a pass. unless a wire is broken the cruise should be seeing the vss signal as well.

 

[Gemmell]

I'll have to recheck the voltage and get back to you on that. Continuity is good from the pcm to the cruise module, I haven't checked to see if that circuit is grounded out somewhere tho.

Thanks for the help!

 

[Gemmell]

I believe I've found the problem. when I was finally able to recheck the voltages the vss signal was reading .04 of a volt. Even with an analog volt meter this wire is almost lifeless with the rear wheels turning. I traced it back and it goes to the vss buffer unit. although there is continuity from end to end, there is also continuity to ground. Is there any notorious locations for wires to wear through? otherwise I'll just be running a fresh wire.

Thanks!

 

[SunlitComet]

nothing in a tsb. just try a new wire first.

 

[speedtechlights]

I think the wire is the problem, try a new wire first.

 

[Gemmell]

I actually ended up finding where it was grounding out. The previous owner installed an aftermarket cd player and left a few unused wires stripped and bare. One of them being for a speed/volume control for the radio. As expected it was being grounds out. So glad it turned out to be really simple.

Thanks for the help!