Let's see I bought this truck last Friday and the check engine light came on Monday morn. Typical for me.
Dealer says it's a transmission control module, but I don't have any drive-ability issues that I have noticed. Service adviser claims it will be 2-3 weeks before he can get parts for replacement and that it won't hurt to drive it.
Sooo other than the check engine light, what are the other effects of this not working properly?

 

Shifting issues could take place. harsh shifts from gear to gear.

That was my experience. Mine was bad when I bought it.

Replaced at 600 miles. Been fine ever since.

 

Yep, evidently mine too.
It's new to me, so I don't know what it was like before.