'730 ecm
aftermarket VSS from Arizona TPI.
I installed the vss and dialed it in at 4981 pulses per mile, using a buddies Genisys scanner. It was acurate mile for mile w/ my GPS (I have no speedometer to go by so I use GPS).
Now I get setup w/ tunerpro RT and the mph is outa whack. At 55, it reads around 30, and about 36 while im doing 60.
Ive tried changing the pulse counts (im using 8D xdf), but they have NO affect on the mph readings in TP RT. I also changed the vss speedo divisor from the 0 it was at to 125 just to see if it would have any affect..... That change TOTALLY stopped the ALDL from connecting to the laptop ( whats that all about?)
I rechecked w/ the Genisys scanner the make sure the new VSS didnt crap out on me, and it was still spot on accurate (after I changed my #'s back).
This leads me to believe something is not setup correctly in my tp rt program even though everything else looks normal.

please help, jeff

 

Ive been reading about the speedometer scaling and dividers, but I believe that only applies to slowing the speedo down, I need to speed mine up.
I gotta wonder if my settings that are controlled by mph will work correctly.
I suppose I could set the speed limiter for 55 mph and see what happens:-)

 

give FIRST THRID GEN 1227730.ads a try.
its at, http://www.moates.net/info_pages.php?pages_id=14
then look in " Datastream Definitions "

 

Ok, Im on the way out to the garage now to give that a shot.
I also loaded 3 others that are for the '730.

I just find it odd that the genisys scanner sees one speed and my setup is seeing something totaly different.

 

OK,
I tried the, firstthirdgen 12227730 .ads, (and the other ones I found) but there was no difference.
I found that when using the speedo divisors, there are only set #'s that can be used (Found these here by doing searches for speedo calibration), altough this didnt matter since it didnt change my mph display.
I did test the "fuel cut off vehicle speed" setting.
when I set it to 56 mph, it did nothing (took it up to 70mph {gps})
then I set it to 36mph, somewere around 57mph{gps} it fell right on its face (kinda made me smile cause I new I caused that,LOL).
Now I know that the speed that TP is displaying IS the the speed theEcm is using. It still makes no sense why its so far off.

So I started playing w/ the "VSS pulse per mile" setting again.
It now seems to be having an effect on the mph, but, at its lowest setting of 3614.12 ppm its still of by about 8mph (TP reads 47 while GPS says 55mph).
Is there a way to get that # smaller?
If I punch in, say, 2000, and hit save. Then reopen it, it will be right back at 3614.12. Sometimes it prompts me that the XDF has been modified do you want to save? I hit yes, but it will still stay at 3614.12.

need some help here, jeff

 

are the drive and driven gears in the vss as close as possible to what your rear end gears and tires need? that might put you just outside of the correction window allowable thru the prom settings.

 

Ive got no idea what the speedo drive gear is in the tail housing (turbo 350 tranny), the aftremarket VSS is listed as 4000 ppm.

anyone know how to change the XDF to let that # go smaller for the PPM?


Also, what is the Genisys scanner looking at to get different mph #'s?

 

3614 is the lowest you can set it to. its a limit in the code of the ECM.
i have always used 1227730_8d to set the VSS gear ratio because its setup to give you the Vss ratio setting from 1 - 255 instead of pulses per mile. max setting low 255 = 3614, max setting high 1 = 921600

Norwood is on it, your not getting enough pulses per mile to get a close enough speed reading. so you'll need to do some gear swapping to speed up the signal.

i don't know what the scan tools use to get the speed reading, i assumed it was the same as what TunerPro used.

 

OK, I just changed the speedo gear from a 41 tooth to a 35 tooth. Without changing my PPM on the chip (left it at min setting of 3614.12 ppm), the TP readout is now accurate. I guess I got lucky finding that gear in my friends spare parts pile. I would have liked to have gotten a smaller one (tooth count) so that I had room to play when I change tire or gear size. Oh well, now I know what needs to be done so I may have to spend the $20 for the correct one ;-)
Thanks to those that replied, If anyone has an answer to why the other scanner was reading different, I would still love to know.

thanks jeff