This style of remote is found on TH, TJ, TL and TW Magna and KH, KJ, KL and KW Verada between 1999 and 2005.
Common problems with these remotes are a loose, broken or totally disconnected battery holder, broken clips or tags on the holder and dry, cracked or broken solder joint causing the remote to work intermittently. A loose, cracked or broken battery holder may sometimes work long enough to allow you to program to your vehicle, work a few times but then stop suddently; normally the first time you drop your keys!
Unlike some tutorials you may find online, we do not cut your battery holder and we do not recommend it!
Becoming more common due to the age of these remotes, the buttons start sticking or become totally stuck with a greenish-brown residue on the buttons, PCB and rubber membrane. In an attempt to get it working, people try pushing their buttons harder which only damages the rubber membrane. For light build up solvent will normally work, however if they are sticky to touch they may require rebuilding or in the worst case replacing.
Unfortunately, in most cases buttons for have been stuck down (wouldn't move) and needing rebuild will lose their 'click' feel and sound but will function electrically as required brining the switch back to life.
Quite often too, owners are not told by their dealer that the battery can be easily replaced if they have a flat or low battery. A low battery will make seem like a broken remote in that it will have enough charge to be programmed into the car and work a few times but then stop.
To add to your vehicle, have all the remotes you want to programme together (must all be done at the same time). All previously programmed remotes will be forgotten by the vehicle and replaced with the ones being added.
For additional details, refer to the vehicle handbook (section 14-7 for TL).