The VSS, where to check for wiring problems?

[Need4Camaro]

97 Chevy Camaro.. Speedometer goes haywire. I mean sitting still it'll bounce all the way to 55 MPH and when I'm moving it gives way inaccurate readings... Like it will bounce up and down and at times, it will catch on and display the speed just perfectly fine like nothing is even wrong so eventually, I literally unplugged the VSS and found that it still does the same thing when I just start up the car. It bounces up and down all the way to 55 MPH and down and up again but it's completely unplugged!!! So it's definately getting some sort of power somewhere. I checked for crimps in the wire and found one crimp in a yellow wire that went straight to the O2 sensor after Cat... I don't think that was the problem as when I repaired it, it still did the same thing. I have replaced the VSS and still no go... I checked what LITTLE wire that I possibaly could under the tranny and found nothing wrong... I am a bit hesitant going under the dash as they seem a bit fragile and I don't want to break it trying to find the entrance of the wires to the firewall... Any other thing I can check? or should I just drop this thing off at a Mechanic?

[nda0602v6]

I'm still working on the speedometer on my 94 Camaro. The yellow and Purple wires that plug into the VSS work their way over the top of the bellhousing and are attatched to the firewall. From there they enter the thick main wiring harness that runs along the back of the engine (you can see it with the hood open, it works its way around the firewall and over to the computer).

Using a volt meter and with the VSS unplugged, I tested the Yellow (+) and Purple (-) wires at the plug. According to my Haynes Manual, I should be getting a reading of roughly 5-volts. The only reading I get is 0 to 0.02 volts. I tested it right at the computer and it still reads the same. I'm thinking the computer is bad. Do you have a volt meter? Try testing your plug and see what kind of voltage you get. Test for DC-voltage, Yellow is the + and Purple is the -.

[Need4Camaro]

Originally posted by nda0602v6:
I'm still working on the speedometer on my 94 Camaro. The yellow and Purple wires that plug into the VSS work their way over the top of the bellhousing and are attatched to the firewall. From there they enter the thick main wiring harness that runs along the back of the engine (you can see it with the hood open, it works its way around the firewall and over to the computer).

Using a volt meter and with the VSS unplugged, I tested the Yellow (+) and Purple (-) wires at the plug. According to my Haynes Manual, I should be getting a reading of roughly 5-volts. The only reading I get is 0 to 0.02 volts. I tested it right at the computer and it still reads the same. I'm thinking the computer is bad. Do you have a volt meter? Try testing your plug and see what kind of voltage you get. Test for DC-voltage, Yellow is the + and Purple is the -.

Okay.. Curious where you able to get into your PCM to check the wires before the connectors? How do you open the PCM?

[nda0602v6]

isn't the pcm the same thing as the main engine computer? The unit I checked is tucked in the corner of the engine compartment, back by the firewall (on the passenger side). I removed what I assume is the engine computer in that location and located the VSS wires that plug into it and also found two green w/white striped wires there as well. I never actually opened or went "inside" the computer, its sealed shut.

[Need4Camaro]

Originally posted by nda0602v6:
isn't the pcm the same thing as the main engine computer? The unit I checked is tucked in the corner of the engine compartment, back by the firewall (on the passenger side). I removed what I assume is the engine computer in that location and located the VSS wires that plug into it and also found two green w/white striped wires there as well. I never actually opened or went "inside" the computer, its sealed shut.

I see I see, How did you remove it? Where on the PCM? What bolts?