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what is the vss and its meaning?

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what is the vss and how can i tell if its hooked up or not

I am probably the least qualified to answer this, but I'll try anyway.


VSS = Vehicle Speed Sensor


It's found in many cars, but not all. It is usually a wire that carries a pulse signal that is generated from a device that is connected to the drive shaft or wheel. It produces an electronic pulse (or 2, or 3 or whatever) each time the drive shaft or tire goes around. This signal may be used in different systems in the car, from ABS, to the speedometer, to the speed compensating volume on the radio.


For example, in a 2002 Ford F-350, if you simple hook up the VSS wire to a particular pin on the back of the radio, the speed adjusted volume will now work. The faster the pulses come pouring in, the faster the vehicle must be going, so it jacks the volume up. The feature was always built into the 6 disk CD changer radio, Ford just didn't hook it up unless you purchased the upgraded interior.


From what I understand, in an AVIC-Z2, the "navigation system" (I used that term on purpose, because it is more than just a GPS receiver) takes the vehicle pulse count from the VSS and compares it to the GPS. The system will determine that it takes XXX number of pulses to go 1 mile. The sytem is constanty learning and comparing the pulse count to the GPS signal. It does this because as the tire wear out, the diameter of the tire gets smaller. A smaller tire will have to rotate more to go the same 1 mile, creating more pulses per mile.


OK, so what does that have to do with the GPS? The GPS always knows where the vehicle is, what the heck does it do with the VSS signal?


If you are traveling on I-95 in New York and end up in the lower level of the George Washington Bridge, or some how end up in the Holland Tunnel, or drive down Broadway in a "concrete canyon," or in a Vermont valley on the north side of a very step hill with a tree canopy over the road, you will loose the GPS signal and the rather expensive navigation system becomes a useless piece of junk until it sees the sky again.


So with acceleration sensors for turn, a connection to the VSS for distance, a connection to the back up light (so it knows that the distance is reverse and not forward), the "navigation system" will still do a pretty good job of getting you to where you want to go when the GPS signal is lost for a while. This part of the nav system is call "dead reckoning," click here.


On a AVIC-Z2, click on Menu> Settings> Hardware> 3D Calibration Status

From there you will see an item for "Speed Pulse". I drive a Saturn Sky and I've been told that my car does NOT have a VSS wire (but I'm still looking around to confirm this). In my case, I would have to put on an aftermarket pulse generator that Pioneer makes. Because I don't have a VSS wire hooked up to the unit, mine says "0" and it also says below that, "Simple Hybrid".


When the unit is turned on the first time it "initializes" to see if the VSS is hooked up. After a while of driving if it does NOT see a VSS signal, it will do "simple hybrid" dead reckoning. If it does see the VSS signal, it will use "3D hybrid" to determine position.


After it has learned your car by comparing it for miles and miles, it uses the 3d or simple hybrid to determine position when the GPS signal is lost. Exactly what the difference between the two is, I don't know. But 3D hybrid is supposed to be more accurate because it can use the VSS pulse to help determine position.


BTW, when your replace your old tires, even with the same brand and size, the pulse count will change. For this reason, you can go to the 3D Calibration Status page and reset it to wipe out the learned data from the old tires. You would want to do this so it won't have any old data to have to average in to its calculations. If you didn't do this, it would still learn the new tires, but until all the old tire data is replaced with the data from the new tires, the calculation would not be that accurate.


OK, I'm done. I'll put on my flame suit now and wait for all the corrections that I'm sure are coming. :D

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EDIT: for some reason I assumed you have a D3 unit. If you don't, this probably won't help.


VSS means vehicle speed sensor. It tells you car how fast it's going.


To see if you have it hooked up correctly, you can do a couple of things.


1 - While viewing your nav map, hit the map button. That will bring up a menu of view modes. Hit the vehicle dynamics button, and three dials will come up. The center one is your speedometer. If it doesn't register your speed while you are driving, your VSS signal is not making it to the D3.


2 - Hit menu while in navigation mode. Go to the settings tab, and select Hardware info. Select 3D Calibration. If (while driving) the number to the right of "speed pulse" reads zero, your VSS signal is not making it to the d3.

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