The only way to program keyless entry is with a very expensive diagnostic tool called "Launch" or go to nearest dealer for programming.
dealer has to do it with factory scan tool
You have to program it with a DRB (Scan tool).
I had the same problem. Google "keyless entry remote 2003 Jeep Grand Cherokee".
Use the key. The keyless remote only unlocks the doors and doesn't govern how you start the car. If you can't get in the car, try using the ignition key for the door. Sometimes the two are keyed the same. Otherwise, you're going to have to get a new keyfob.
Sadly this is gonna require a visit to the dealer. Plan on spending $40 or so to get this done. Every Jeep from 1996 or so onward will need a dealer program to get keyless working.
Possible weak battery in the remote.
it has to be done by the dealer. =(
centre top dashboard (red dome)
Go to your local locksmith. Most have the "box" to program a remote. I paid 20 bucks for 1 remote.
Dealership
You must contact a local Dodge, Chrysler, or Jeep dealer. They need to program it using the vehicle's diagnostic computer system. It will likely cost around $30; you might be able to go to your original dealer and get them to program it for free. Good Luck!
YOU CAN FINE ALMOST ANY KEYLESS ENTRY ON EBAY AND FOR A GOOD PRICE.. GOOD LUCK.........