I have 2 remotes that DID work. I unhooked the negative side of the battery to remove the radio and install an aftermarket radio. After install, my remotes didn't work. So I went to reprogram them and after I hold down unlock and cycle the key on and off twice, I can hear the programming start... then 3 seconds later the truck locks and unlocks and the horn beeps to signify programming is over. Does anyone know a fix for this..... not really sure why this is happening. I even installed the old radio to make sure that wasn't it and it still did it. I cannot program the remotes and I have followed the directions to a "T"... Please help

 

You can google and find your particular make/model. As example, my 1999 Tahoe has a port under the steering wheel area that has two rows of pins. The TOP ROW is number 1-8 starting
on the left side. Use a paper clip and JUMP from 4 to 8, then the locks will automatic cycle. After this hold down the LOCK/UNLOCK button on the remote that will activate the locks again, programing complete.
David g.