Just got my transmission replaced and everything worked fine for a few hours then speedo went out CEL turned on and a little after that my idle went up. Anybody know what the problem could be? Easily fixable? Thanks guys!

 

You have two different problems. The car won't throw out a CEL if the transmission has a problem because you have no wiring connected to the wiring harness and the speed sensor goes directly to the cluster..

 

yes, it must be the VSS cable, if you swapped transmission, maybe it pop out if it wasnt deep enought/locked in the vss (this will cause the CEL)

 

Yes, should be an easy fix. The VSS/ Speedo cable probably popped loose from the transmission. Happened to me when I replaced my 4 speed with a 5 speed. When you put the cable back in, make sure you turn it when putting it in. I didn't do that and it popped out and the speedo stopped working and got a cel code. If it is already in tightly, check to see if it is connected to the cluster securely.