Aftermarket Electric Speedometer
 

For those of you that have added a speedometer controlled by your ECM

What brand of speedo are you using ?
What is the signal that is produced by the ECM?
Does the transmission VSS make a difference if it is a 4L60E or a 4L80E
or is the "magic" controlled by the ECM and not the VSS?
What Pin or Pins control the speedometer and what is the signal that is transmitted to the speedometer?

Re: Aftermarket Electric Speedometer
 

I'm going to assume we're talking about Gen 3 PCMs since that seems to be what most folks are using.

The PCM outputs a square wave with an amplitude of 12V and a frequency that varies with vehicle speed on pin 50 of the red or green connector (depending on whether you have a "red/blue" or "/blue/green" PCM).

The VSS output defaults to 4000 pulses per mile (4K ppm), but can be changed in the tune.

4l60 and 4l80 both have 40 tooth reluctors on the trans output shaft and the VSS sensor reading the teeth on that reluctor wheel outputs an AC sine wave that increases in both frequency and amplitude with speed.

Most speedometers are going to want the square wave from the PCM and not the sine wave directly from the VSS.

Re: Aftermarket Electric Speedometer
 

I have a combination of a 2003 4l60E and a late model LS3

Thanks with that info I think I can answer his questions


I don't have the ECM in front of me but is a new ECM and the engine runs and the trans shifts, working on the dash speedo and Tach next
I can get an electric conversion for the tach but I can only use the stock speedo "Face"
which has a 180* sweep

Re: Aftermarket Electric Speedometer
 

Will there be a description on the aftermarket speedo to indicate what signal it needs to make it read MPH

Re: Aftermarket Electric Speedometer
 

I used a Dolphin electronic, 8k was the setting I believe.