MegaMan X Posted March 10, 2009 Report Share Posted March 10, 2009 So I've had my avic f90bt installed for roughly a month now. How do I verify that the VSS wire is working? I read that it takes some time to calibrate it, which the headunit does automatically. When I'm driving around, and I go into the navigation system settings to take a peek at the MPH, it doesn't match my speedometer. I have stock steelies, so I know it can't be the difference of my wheels and speedometer. The difference between what it says in the avic and speedometer is off by ~1-2mph Are there any mods, or settings I can tweak, so that I know the avic is receiving a signal from the VSS wire? (well, besides driving under a tunnel...in which there are no tunnels near me, and I'm not willing to drive out of my way to a tunnel...LOL) Quote Link to post Share on other sites
BorisM Posted March 10, 2009 Report Share Posted March 10, 2009 So I've had my avic f90bt installed for roughly a month now. How do I verify that the VSS wire is working? I read that it takes some time to calibrate it, which the headunit does automatically. When I'm driving around, and I go into the navigation system settings to take a peek at the MPH, it doesn't match my speedometer. I have stock steelies, so I know it can't be the difference of my wheels and speedometer. The difference between what it says in the avic and speedometer is off by ~1-2mph Are there any mods, or settings I can tweak, so that I know the avic is receiving a signal from the VSS wire? (well, besides driving under a tunnel...in which there are no tunnels near me, and I'm not willing to drive out of my way to a tunnel...LOL) Apparently there's some screen you could access with Pioneer's diagnostic CD... On the other note, pretty much all car speedos are off a few mph by design. I have never seen one that would match any GPS exactly. Quote Link to post Share on other sites
joegr Posted March 10, 2009 Report Share Posted March 10, 2009 As BorisM says, most (if not all) cars speedometers are off by a small amount, usually on the fast side. As your tires wear, the difference (between the reading and true speed) will vary. The easy test for VSS operation. Put a large piece of metal over your GPS antenna. You should get the verbal message "GPS signal lost." Now vary your speed and see if the reading on the AVIC tracks with the speedometer. (It'll still be off by whatever amount.) Quote Link to post Share on other sites
MegaMan X Posted March 10, 2009 Author Report Share Posted March 10, 2009 shoot, my GPS antenna is actually underneath my dash...no way to put a giant metal sheet over it....I dont even have a metal sheet LOL well, I use wire taps for the VSS wire, so hopefully its working still Quote Link to post Share on other sites
1loudls Posted March 11, 2009 Report Share Posted March 11, 2009 shoot, my GPS antenna is actually underneath my dash...no way to put a giant metal sheet over it....I dont even have a metal sheet LOL you can put a piece of metal over the dash where the antenna is Quote Link to post Share on other sites
MegaMan X Posted March 12, 2009 Author Report Share Posted March 12, 2009 shoot, my GPS antenna is actually underneath my dash...no way to put a giant metal sheet over it....I dont even have a metal sheet LOL you can put a piece of metal over the dash where the antenna is like i said, I don't have a piece of metal lying about...haha Quote Link to post Share on other sites
mtnbiker717 Posted March 12, 2009 Report Share Posted March 12, 2009 A couple sheets of tin foil layered should do the trick Quote Link to post Share on other sites
DragonRM Posted March 12, 2009 Report Share Posted March 12, 2009 Yeah... coming from an auto tech standpoint, most vss are off and lose accuracy on the very low and high side. The GPS is usually a more accurate readout as long as you're holding the same speed. I haven't hooked mine up yet (mostly just being lazy) but it's off by a few mph too. Seems to be there mostly to help in the spots where you lose the signal for a few seconds. Quote Link to post Share on other sites
zerog270 Posted March 12, 2009 Report Share Posted March 12, 2009 Using a voltmeter, you can measure the VSS wire in volts AC and it should read between 0.1 and 0.7 volts and while you are driving the volts will go higher. If you stop it will level off or if you go at a constant speed. -Mike Quote Link to post Share on other sites
joegr Posted March 13, 2009 Report Share Posted March 13, 2009 Using a voltmeter, you can measure the VSS wire in volts AC and it should read between 0.1 and 0.7 volts and while you are driving the volts will go higher. If you stop it will level off or if you go at a constant speed. -Mike That only applies to some VSS signals. Many are now digital square waves that only vary in frequency as speed varies. Even with those that put out sine waves, it is better to measure the frequency, because that will be proportional to the car's speed. Quote Link to post Share on other sites
DragonRM Posted March 14, 2009 Report Share Posted March 14, 2009 Yeah... a lot of vss signals are 0-5 volts on/off reference voltage. Quote Link to post Share on other sites
inches805 Posted March 15, 2009 Report Share Posted March 15, 2009 If you have a light tester it is even easier. Just plug the light tester into the wire, if it pulsed between red and green as the car moves, you have the correct wire. (remember though, not all light testers are created equal. Some cheap ones can do damage...) Quote Link to post Share on other sites
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