DTC 24/ No Speed logging in '95 Corvette

[n8sh4de]

Hi Guys,
this problem is existing for many years since my auto to manual swap. After correcting the VSS data in the PCM (40pulses per revulotion to 2 pulses, with a 3.08 axle) I get the correct speed on the speedo, but also a DTC24 VSS error when shifting from 1st to 2nd gear. Last week I logged during driving and saw that no speed under 30mph is logged. The problem is similar to this thread, but i didnt find a clear answer what he did to solve this. http://www.gearhead-efi.com/Fuel-Injection/showthread.php?7591-86-Vette-with-94-LT1-Help-NEEDED!!&highlight=Dtc24

Any ideas? VSS wrong or broken? (Is this even possible?) I also checked the wiring, the PCM gets a signal from the VSS. A sinus curve with low amplitude and frequency at low speed, and high amplitude with high frequency at high speed.
Or maybe wrong numbers in the PCM for the VSS calibration?

And why does the PCM give the right speed to the CCM but I cant log this speed? (Sometimes around 1-2 mph the CCM shows things like 197mph, the oscilloscope shows very fast random pulses in this speed area)

EDIT: Could too low VSS Voltage cause this problems? Is this a common problem with faulty sensors? The resistance of my Sensor and wiring is 385 Ohm..

I hope you can help me!
Best regards,
Max

PS: Sorry for the spelling, I'm writing at a mobile phone with autocorrect in the wrong language :D

[n8sh4de]

Finally, 4 years later, I solved this problem. :rockon:
As the car is an auto to manual swap, my new configuration was still based on a .bin for an automatic transmission car. I used all tables from a .bin for a manual car and deactivated the automatic transmission.
After the new VSS sensor didn't work either, I flashed an unmodified bin from a manual car, and boom, it worked!
Obviously there are some important bytes in the "unknown values" region that are needed to get the VSS input working properly!

So you always need a manual .bin for transmission swaps, not just change the speedo scalars!:thumbsup:

I'm just still trying to find out why the speed on the speedo and on the loggs are different. At 100 kph speedo, my log says 73kph...