Ya it splits and converts the speed sensor signals to everything that needs it. Kinda strange that they were using em so late on our trucks. Most things by that time ran off the main ECU. Its also where you can calibrate the speedo if you changed rear end or tire size. I'm not sure if they still do it but there used to be places that would recalibrate them for you or sell you one that had switches on it so a only slightly above average person could calibrate them on their own.
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