As previously posted by Terry Mason , what year engine and from what model ? Yes , will you be using the same PCM ? Assuming your keeping the PCM if there were no issues with it , your main concern with the replacement engine will be mainly the ignition system and cam sensor. If it is an earlier year engine and the cylinder head casting dosen't have the mounting locations for the DIS coils , that can make in installation difficult. Also , the earlier year ( 1999 and earlier , I believe ) have a distributor and not distributor less ignition systems (DIS) . From your current engine ( the soon to be sailboat anchor) you will need the cam shaft position sensor in its entire. Just remove the entire unit . If installation instructions are needed , post back. You can turn the busted engine to TDC #1 piston on compression stroke and see where the cam sensor aligns and the oil pump shaft is clocked for easier install for the new engine. Also , check the flex plate if auto trans if there is any difference. There shouldn't be but make certain. Remove everything from the old engine in case something is needed. Don't discard anything until your new engine is running since it's possible something may be needed. Now , back to your original question .
You were asking if the engine had any differences with regards to the factory security system (chipped key) . The engine swap wouldn't have anything to do with the security system EXCEPT you'll be disconnecting the battery . This is where the problems start. Things like radios and anti-theft systems need security codes and/or passwords. Codes are set upon battery replacement passwords are needed if difficulties arise . It's just like when you mess up signing in to an online account and the password is forgotten. You see where I'm going. Before you disconnect the battery on the jeep with the old engine , know the security code for the security system and radio. These systems are supposed to reset if battery is connected immediately but only in a perfect world. If you try to use a 9volt battery jumper , you may have a chance. It's supposed to work. Someone in my dad's neighborhood had his SUV ( non-jeep) towed to dealer to get this sorted out . So much security questions and owner verification . Everything but DNA samples. Don't let this happen to you. If your unsure about a possible , consult a dealer . Maybe an authorized alarm installation center can help but the dealer is best. I don't mean to scare you out of this swap since it is just a motor swap but things like this could happen and its best to be prepared. The guy who's SUV was towed to dealer wa just swapping out a battery. It was installed same day but probably hours later and the PCM and body control modules must have drained all stored voltage . Guessing the battery cables both grounded under the hood and drained the capacitors in the PCM and body control module. I'm writing this because your 2004 GC will have systems like this too. Be prepared before you proceed. Hate for you to successfully install the engine and find a no start upon completion . Find out what you can regarding the security codes and reset procedure. Factory shop manuals have these but the dealer should be helpful . I'm no expert at the factory security systems reset but I know this can be an issue. Hope this helps . Best of luck on your swap .
