what are those pulses measured in ? are they in mA ? V ? what

i have 2000ppm in my 91 tbi formula nd my 4th gen guages are 4000ppm speedo, and i understand that at rest there is 0 volts an at top speed its 5 volts... but what is the pulse per minutes measured in ?

i have a dakota digital box... and it corrects the speedo but i would just like to know what i am correcting

 

Actually the signal generated by the VSS is a SINE WAVE that is processed into a SQUARE WAVE by the ECM. There are two solid state output switches and each output terminal is switched to ground at a rate that is proportional to the speed of the car. The speedometer is switched at the same frequency that the ECM generates, 4000 pulses per mile. The cruise control operates at a much lower frequency of 2000. BTW, your 91 speedometer operates at a frequency of 4000 PPM just like the fourth gen one does. BTW, the sine wave is actually a frequency of Alternating (AC) current voltage. In the service manual there are several diagnostic tests to determine the servicability of the components in that circuit. The unit of measurement that you will be checking for is voltage and the maximum voltage that you will checking for is battery voltage for the ECM test and 5 volts for the other portions of the test.

 

ok, then what was changed between the thirdgen and 4th gen 4000ppm sine waves ? i needed the sig5 box to make my speedo work, could it have just been a bad/loose groud on the cluster itself ? now that i have the issue fixed with the box, ia m trying to understand it more, to see why exactly i needed the box and if a inline resistor, or capacitor or potenimeter, or something to that effect could have solved the problem instead

 

without sgi-5 box - did you have the wire come from the 3rd gen buffer box or directly from the vss on the tranny?

What happened without the sgi-5 box?

 

with out the sgi5 box i had the needle jump around to random speeds ransomly as i was driving from zero

and with out it, it was in the stock set up... aka

tranny to buffer box, to ecm to guages

 

maybe you had a loose electrical connection somewhere. it should have worked without the sgi-5 box. I wouldn't worry too much about it now since your car works. If it isn't broke then don't fix it.

 

exaclty it should work wiht out that $80 box and if i can make it work i will, i seriously doubt there is a loose connection... as i was meticulous about my electrical connections... i just want to know why it didnt work, and if there is a simpler way to fix it, aka inline capaciter or resistors...

 

a single cap or resitor in series wont fix this problem...you need a whole bunch of parts like whats in the sgi-5 box or the buffer box. Maybe the sgi-5 box works better? Maybe with your old setup you have your wire too close to another wire its picking up voltage causing a distorted output? I haven't swapped a 4th gen dash so i dont know what is normal.

 

i understand that there is more then one resistor or capacitor... that is wha ti am trying to figure out...

the guages are all messed up, everything worked but hte speedo, i was told by multiple sources that i should have been able to just hook it up and go, but it didnt work, i also know people who should have had to get buffer boxes for hte speedo and the tach and they hooked it up and went and it worked with out them.

 

Are you certain the 4th Gen guage cluster was intact when removed from the donor car?

 

yes i tried several actually

 

Hi
I have tryed some conections with VCC and speedo.
This is what I have expired.
The VCC signal is not stong enough to drive the speedo and computer, like TCU.
I don't know about your coneciton, but this is what I have expired.