My GPS is a lot more accurate then my speedometer, lol

You could probably connect this to the vehicle speed output pin from the PCM.

Blue connectors pin 55 (drk green wire)

X2 again.

GPS can give very accurate speed. But they dont give accurate location. Location is 9 yards i think?

But once your moving its very easy to figure out the speed.

I have no idea what HU the OP is using.. And GPS sped is only as good as how many birds you have Eclipse uses 4 speed is out but +- 2 -4 mph it'* a feature that is there to give the actual speed of the vehicle, DI I ever use the Speed Pulse wire on a install NO but with the new eclipse units it displays a msg check sped pulse. most times it is a pita to route and hook up that one wire.

the wire needs to go to the VSS where ever that is. just tap into it and your set. Dont be shocked tho if you get a SES light, I have seen and read about that in the past.

The VSS will give you pulses of rotation (its in the differential housing) but without knowledge of pulse per mile (in the PCM) which varies based on gear ratio this data would mean nothing?

BTW after thinking bout this feature I guess if you are in a canyon area or in mountain tunnels you would loose GPS navigation so having speed maintained via the car sensors is sort of a backup....

My TNR800 also requires a connection to the VSS. One of the reasons is for the GPS to continue to operate more accurately even during brief losses of GPS signals. This connection is not surprising at all. The aftermarket portable versions don't use this, but I've found my in dash unit to work much better in some respects.

There is a VSS signal present at the HUD (if equipped), as well as the instrument cluster in your car.

On the HUD connector, it is pin A8 and the wire is DK GRN/WHT.
On the instrument cluster, it is pin B4 (of the 12 cavity connector). The wire is also DK GRN/WHT. The second connector has 16 cavities so you should be able to distinguish the two easily.

Also of help is that the wire is the only DK GRN/WHT which goes to either of the instrument cluster or HUD connectors.

The VSS is designed, regardless of gear ratio etc, to provide 4,000 pulses/mile. It is easy for the vehicle components to compute speed based on time between pulses.

As a bit of miscellaneous info, ever wonder why there is sometimes a slight discrepancy between the speedo and HUD number? Because each component calculates the vehicle speed independantly. Slight differences due to tolerances etc. can result in this variance.

I have a custom reluctor wheel (different amount of teeth) on my differential that the VSS reads due to the gear change in the car. I'm guessing the speed would be off in this scenario.

See next post. Double entered for some reason.

This doesn't surprise me then. In a strictly OE environment, GM designs this system to provide the 4,000 pulses per mile based on all orignal parts. If any of these change, you would very likely have a different number of pulses per mile and your speed wouldn't be accurate. The alternative is that your wheel has a different number of teeth to compensate for the different gear ratio in which case your speed would be accurate.

answer for willren i got it installed at class a audio in albany i was going to go to the stereo store but it was 50 bucks more and its taken them over 2 weeks to get the 110 dollar harnes witch class a already had in stock. but the 1st post i gave has the link to the head unit. its a avic-d2 pioneer... i spent 275.00 getting my stuff installed i want it all done right