fusion_ta66

iTrader: (1)

Hi guys,
I have read through a bunch of threads but I'm still a bit confused. I am running a '99 LS1 with a tko600. I have been advised to use VSS to give better driveability, and I definitely want the best driveability. I am running a mechanical speedo.

There are 3 VSS wires on the PCM.

Pin 20, Low VSS signal
Pin 21, High VSS signal
Pin 50, VSS signal

Question 1) I am assuming the Low and High VSS signals are giving information FROM the trans TO the PCM, and the Pin 50 VSS signal is sending information FROM the PCM to an electronic speedo (which I don't have). Is this correct?

Question 2) I am assuming I get the VSS signal from the trans from the wire connector on the passenger side of the trans. It is a 2-wire connector. Is one wire is High signal and the other is Low signal? Which wire is which? How do the wires get hooked up to the PCM?

Question 3) I believe I need to convert the signal from the trans to adapt it to a different pulse rate that the PCM can read. How do I accomplish this?

Question 4) I have read that my gear ratios in the trans and rear end both impact the VSS signal. Is this inputted in the tune for the PCM?

Question 5) What is the difference and purposes of the 'VSS high' and 'VSS low' signal?

BONUS QUESTION: How do I hookup the neutral safety switch on the trans (2 wires) to pin 34 "Neutral Safety Switch" on the PCM


Thanks in advance
Joe

truckdoug

iTrader: (25)

question 3, there is a thing you can run from your mech speedo output that sends a vss signal. its either from jags that run or dakota digital.

sorry i cant offer much more than that. i was lookin at that same set up, but chickened out and used the slushbox.

fusion_ta66

iTrader: (1)

Anyone? Help!

tommyboy

i've also read that the vss signal either needs a very accurate mph signal or just if the car is moving or not....which one is it?

Just wondering bc some swap chassis has there own vss signal that can be sent to the gm ecu.....seeing how accurate it needs to be.

garys 68

iTrader: (1)

1 yes
2 If one wire is grounded to the VSS metal body or coax sheath, that's low. Otherwise doesn't matter.
3 Don't need to "convert", you program the ecu to recognize the correct speed.
4 see 3, although for stalling issues, the correct speed is not needed, only for correct speedo output (you're not using), or DBW cruise control.
5 2 wire vss puts out sine voltage, no real difference.
Bonus, you don't hook it to the ecu on most conversions. You can use it to interrupt your ignition to starter "crank" wire.

fusion_ta66

iTrader: (1)

Thanks for your comments Gary. I didn't understand this comment:

2 "If one wire is grounded to the VSS metal body or coax sheath, that's low. Otherwise doesn't matter."

There is a pigtail coming off the side of the trans that has a plastic 2-wire connector. I'm still not sure how to figure out which one is Low and which one is High, if the TKO even outputs 2 signals. And when I figure this out, I still don't know how to hook up to PCM. Does the PCM require both low and high signals?

garys 68

iTrader: (1)

Just hook up the 2 wire sender to pins 20, 21. If it doesn't read speed, reverse them. Note that OEM reluctors turn 17-40 teeth (pulses) per rev. Aftermarket speedo cable driven ones might only be 2 pulses per rev. So a non-recalibrated ecu might only see you going 4-5mph at 70mph. There's no need to recalibrate if not using an electric speedo off the ecu or DBW cruise control.

fusion_ta66

iTrader: (1)

Thanks again Gary. I'm assuming I won't know if the PCM is reading speed unless I hook up a tuner device to the OBDII port while driving?

garys 68

iTrader: (1)

Correct, or if you have stalling issues when coasting to a stop.

gagliano7

There are 3 VSS wires on the PCM.

Pin 20, Low VSS signal
Pin 21, High VSS signal
Pin 50, VSS signal
This is how I hooked up my manual trans in my 1992 chevy pickup to the pcm and to the speedo. You may have to make changes in the pcm to get your speedo to read correctly. I have a 1999 truck pcm.