Hi, Randy, and welcome to 2CarPros.
I have to be honest, a speed sensor is my first suspect, but we can't be sure until it is either tested or you scan the computer for diagnostic trouble codes. Since the check engine light is on, there will be codes stored. I noted that you are a mechanic. Have you checked codes?
As far as speed sensors, there are two on the transmission. One is a main shaft sensor and the other is the counter shaft speed sensor. I attached pictures of both. Check to make sure the wiring to them is clean and tight, not corroded or damaged.
Do this and let me know what you find.
Images (Click to enlarge)
Wednesday, May 15th, 2019 AT 8:17 PM