PT Cruiser key question

All keys are not cut the same. Wouldn't make much sense.

Once programmed for one vehicle, a key cannot be programmed for another.

I think it's the same blank and transponder for them. I don't see why you could not reuse it as a transponder. But the teeth are not likely going to match your new car if that's what you mean by "cut the same".

I see there are eBay vendors selling blanks where you supply the transponder. Why can't the transponder be recoded? Only excuse I can see for that is a need for dealers to suck another $200 from my wallet. There sure isn't much inside. a single surface mount IC, a coil/antenna, and a button battery.

Is the battery replaceable? How long will the Sentry Key work? My 2001 Cruiser uses one. When I first got it, I went to Sears and had four keys made, for the wife and daughters and a spare for the wallet when I locked the keys in the car. Then when I found out they wouldn't start the car, I threw them out. After they were in a landfill I realized that they would open the door and hatch so the one in the wallet would have sufficed.

What battery? The key transponder is either powered by the interrogation signal from the car, or is just a passive resonant circuit. No battery. Similar to modern toll road tags, parking garage access tags, RFID price tags, etc. etc.

The responder has two batteries in series. I have replaced mine for a

Is the transponder (key) programmed for the vehicle, or is the vehicle programmed to recognize the transponder? It would seem to me that the car would be more easily reprogrammed than the "key"... Not that the system designers would necessarily think the same way I do of course...!

Wesley

TO the best of my knowledge the key transponder is just a transponder and isn't "programmed", all the programming is done on the car's computer. Typically they can accept up to 8 transponder codes.

The current keys include both the transponder, which needs no battery, and the remote buttons for the keyless entry, and that does need the batteries. If you buy the simple transponder keys there is no battery and it's smaller.

What I do is get a transponder key and hide it inside the vehicle and a non-transponder key and hide it outside the vehicle. If I lock my keys in I can get in. If I lose my keys I can get in and then get the other key and start it. If anyone finds my non-transponder key they will be able to open the door but not start the car. Most likely having found a key they are not likely to realize they need to continue hunting for a second key.

The batteries are for the RKE. The TRANSPONDER is energized by the halo around the iginition cylinder.

Because they were designed that way. Trying to program a key that's already programmed to another vehicle will fail. Probably security reasons.

Dealers don't design these systems. Go whine to the engineers.

Both are true. The key is programmed with info from the vehicle, and the vehicle is programmed with the key's ID.

The key's ID can be erased from the vehicle, but once programmed, the key cannot be reprogrammed to another vehicle.

The key does get programmed with info from the vehicle.

Thanks for the explalnation. I didn't realize the two parts differed with respect to needing batteries.

That's not true for the Chrysler Sentry Keys, which are manufactured by Strattec for Chrysler. You can program as many cars to a single key as you wish. However it wouldn't make a lot of sense to do that if you want to cut the key and use it, since every car (should) have a different cut. But you could hold up a programmed uncut key near the ignition switch while you used a non-Sentry key to start the car.

That's one way to get a cheaper remote starter to work--just place a programmed Sentry Key inside the steering column. But it also eliminates all security benefits of the Sentry Key.

You can only program eight keys to one car.

Engineers don't set the retail price, dealers do. The Chrysler Sentry keys are often obtained at a much lower price than the dealership sells them for from local locksmiths, etc. Try

What would be the point? I fail to see the logic of it. I'm not saying you are wrong.

I don't know the technology used in those keys, but there are lots of write-once memory technologies: they come from the foundry with all the bits set to 1 (or 0); you can write any bit you want to the other state, but once written you can't change it back. So you can set a code by setting a bunch of 1's, and you can wipe the code by setting all the other 1's. But you can't set a new code.

The clearest example is the original PROM (which is completely obsolete, but still a good example): comes programmed with all 0's. You set a 1 by putting a big enough current through a junction to quite literally blow a tiny fuse. Once you've done that you can't set it back to a 0.

I don't know where you got that information, but it's wrong. A key can only be programmed to one vehicle. The sentry key can only store the information from one module, and that info cannot be changed once it has been programmed.

Dealers don't prevent changing the info stored in the key, which is what the OP was whining about.