In OEM applications the PCM receives both a 40 PPR and 4 PPR signal.
The PCM uses the 40 PPR signal for tranny controls on pin F12. It uses the 4 PPR on F13 for speed and other speed reference functions.
You can use the 2 PPR JTR VSS to the PCM, but it will read low, and can cause some control issues.
In my case I am using a 4L60E, and found out the hard way that I had to use the 40 PPR tone ring and DRAC. For non E tranny applications it would be best to use a 4 PPR, a VSS buffer may be need to condition the signal.
I believe the flag to change from Optical (square wave) to Magnetic (Sine Wave) is called "Output Speed Not from DRAC" in most XDFs.
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