Transponder Relearning

To start a Think you need two things (assuming everything is working properly): a key that is cut to match the key cylinder installed in the car, and a radio frequency transponder that is programmed (learned) to the computers in the car.  This is a pretty common standard for vehicle anti-theft systems.  The transponder is built into the key or fob; when it is brought in proximity to an antenna that is located literally in a circle around the key cylinder the energy from the antenna is sufficient to excite the transponder in the key/fob.  Therefore the transponder doesn’t require any battery power.  The remote lock/unlock/trunk release functions do require battery power, but it is not related to the passive transponder. The Smart Key function in Prius and other cars also require battery power, but when those batteries become discharged the key can still be placed in a slot where the passive transponder can be read by a close proximity antenna.  As I understand it, the antenna essential reads a password from the transponder, sends it to the VCU and PCU (in the case of a Think), and if the password matches what is stored in those computers’ memory, the car starts.  If it does not, there a key icon on top of the center console that flashes angrily.  This system is also commonly called an immobilizer.

There are a few reasons that you might have to relearn a Think’s transponders, i.e. change their passwords.  If the PCU and/or VCU are replaced, the transponders need to be relearned.  If a key is lost and a second one is needed, the transponders need to be relearned… maybe. Some locksmiths can read the existing transponder and program a new transponder to match it.  I’m not a locksmith, so I don’t really know what I’m talking about here.

The procedure to relearn transponders is accessed through Think TechCentre by selecting VCU (Vehicle Control Unit) from the home screen, selecting Guided Routines from the tabs along the top and then clicking on “Transponder Learn” or something like that.  (It’s the only option; you can’t miss it.)  Here are the essential things you need to know about the process:

1. You need 2 transponders to complete the process.

2. It’s going to take at least 10 minutes with the key on, so make sure you have a good, fully charged 12V battery or you’re connected to a 12V charger/maintainer.  Also you might want to not let your computer go to sleep during the process– I just move the mouse every few minutes.  (They call the 10 minutes a security wait, I’m assuming so that they couldn’t make a sequel to Gone in 60 Seconds where they steal high-end Thinks.)

Now, about the 2 transponders: The key actually comes apart into 2 pieces, the mechanical key that is cut to match the cylinder, and the fob that contains the remote lock/unlock/hatch release and the transponder.


If you only have 1 key to a car but you need to relearn the transponders you can use the one key that you have and then promptly (but not hastily) swap the mechanical part of the key over to another fob– any Think fob will do!  The second fob will fulfill the requirement that 2 transponders be present to complete the process; the Think doesn’t care (it doesn’t even know) that the second transponder is already programmed to another car.  The only downside to this is that if the customer does have 2 keys, but has only delivered one to perform this service, the customer’s second key will not start the car.  But at least you will be able to drive it with the one working key until they can bring it back with both keys to do the relearn again.