VSS on 2004 Trailblazer W/ factory Nav

can any one tell me the color and location of the vss wire on a 2004 trailblazer with factory navagation

The VSS wire is GREEN / WHITE at the radio's smaller plug in cavity E.sparky

correct the install went by fast, very easy...

I don't seem to be having such luck. Isn't the small harness for the Onstar? When I disconnect the harness, the radio still is able to function, and the "loudness" control that makes the radio automatically go louder when the vehicle is going faster still functions. I get a 9v or so DC reading from the green and white wire, only when hooked to the back of the radio. When not hooked, I get no reading. I tried the GREEN / WHITE wire on the larger harness without any better luck. Using a voltmeter turned to A/C. Any other locations, I might have better luck? Thanks, Michael

"Any other locations, I might have better luck?" Go under the hood on the drivers side firewall area you will see a module with 2 plugs on it. It is the GREEN / WHITE I believe in the smaller plug. Take a look and let me know if it's there. Good luck, Mike

Thanks - I tried that, I get 12V with the ignition switch on from that wire, no V when ignition off. I don't believe I should see any V when parked. Am I right?

You should be reading on AC volts, not DC volts. Put your meters black lead to ground and the red lead to the suspected wire. On AC volts, it should read little to no voltage with the car parked. Drive the car and the reading on the meter should just up to a volt or more and rise as you go faster, fall as you slow down. Be sure to do this in an open area or have someone else watch the meter so you don't hit anything. Also, make sure you get the car to at least 10 - 15 mph or so just coasting a few feet sometimes isn't enough to really get a good reading. Good luck, Mike

My meter was an older style using a needle to measure my voltage. The AC setting must not have worked well as it always showed me what I was seeing on the DC settings. I purchased a digital meter today and very quickly located my VSS wire. The wire does send 12V DC current, but when measured in AC it does exactly as you described. My question is now, how can I determine the VSS pulse rate measured by number of pulses per mile? Thanks for your help! -Michael

The pulse setting should be at 4000 pulses for the trailblazer. Most common for a chevrolet vehicle.. Mike