remote entry -key fob programming

I have a 1999 Plymouth Voyager and my wife has a 2000 Dodge Caravan.

Is it possible to program my key fob so that it will also open my
wife's car?


John Keith

 

No

 

It's not the fob that's programmed. It's the computer in the vehicle.

I would think it's possible to program both vehicles to recognize
each-others fobs.

The only reason why this wouldn't work is if the fob's operate on
different frequencies or use different coding techniques.

 

Different part numbers, different software. if the part numbers were the
same it could be done.

 

OK, as usual I didn't provide enough info on the original post.

The fobs for the two vehicles were physically simialr so I thought
they might be identical. The facts are:

Chrysler P/N: 04686481AA Same for both
Model/FCC ID: GQ43VT13T Same for both

So my first assumption is that both fobs use the same frequencies and
the same coding techniques.

And I guess I knew that it was the computer in the vehicle that is
programmed from what info I was able to find on the internet, so I
misspoke when I asked if the fob could be programmed.

But then the question is can this computer recognize codes from two
different fobs? The last responder suggests that if the part numbers
are the smae it can be done. So, can anyone point me to the web page
that has the process for 1999-2000 vehicle? (I'll do a little more
searching, but my first pass did not turn up anything for my vehicle.)

And while I'm thinking about it another question comes to mind. My
wife's car originally has 2 fobs that work with it. Are these 2 fobs
coded identically or is the vehicle computer capable of responding to

Thanks for the info so far, hope I can get a little more.

John Keith

 

Though you might be right, that seems counterintuitive.

I have two 2nd gen. LH cars sitting in my driveway that use fobs of the
same part number. If I took the fob of car no. 1 and followed the
programing procedure using car no. 2 and its fob, then both fobs would
control car no. 2, and car no. 1 would no longer respond to either. If
what you're saying is true (that it is the car's computer that gets
programed), that doesn't sound possible. Or would in fact both cars
respond to what was car no. 1's fob after the reprograming?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

That was news to me too - I'd still like to have that confirmed. I was
under the impression that when you went thru the reprogaming procedure
with a vehicle and a working fob to get a second fob working with that
one vehicle, that the second fob was changed (i.e., if it previously
worked with a different vehicle, it no longer would work with its
original vehicle) - I might be wrong.

The answer to that is yes (regardless of whether it is the fob that
changes or the computer).

If you have your owner's manuals, it should be in there.

2 fobs will work with one vehicle.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

I'd say that all 4 fobs (assuming you have 2 for each vehicle) would
work interchangibly for both vehicles.

Maxpower is invited to comment given the new information above.

I went through this a few months ago.

One set of keys for my '00 300m was stolen - along with the fob.

I ordered a new fob and key from the dealer. At the dealer, they
reprogrammed the car's computer so that:

1) the car would no longer respond to the missing fob and
the ignition key-sentry system would no longer function
if the missing key was attempted to be used to start the
car.

2) the computer was programmed to respond to the new key and fob.

3) our other key and fob for the car remained active in the
car's computer.

If the stolen key was used to manually open (unlock) the doors while
the car alarm was armed, I'm told the alarm would disarm as normal.
That would not be desirable. To prevent disarming, I can simply
disconnect a wire in the door that tells the computer that the door
was unlocked manually.

Yes, because in my case, I had 2 fobs for the car (every new car comes
with 2 sets of keys and fobs) and all fobs (and keys with electronic
sentry-key) are unique.

I've seen the dealer do it, and it requires some large-ish
computer-looking thing that gets plugged into the OBD connector under
the steering wheel. I don't think it can be done just by pressing the
right combinations of buttons on the dashboard or console.

ALL fobs are unique, and so are the electronic parts of the keys (if
you have the sentry-key system).

It's a matter of telling the car's computer which fobs and keys to
respond to.

It may also be a matter of how many different fobs and keys the
computer can be programmed for.

 

When all else fails RTFM! The following info was found in teh Owner's
Manual fo rthe 2000 Caravan:

1. Turn ignition switch to the ON postion and leave vehicle in park.
2. Using a previously programmed transmitter, press the UNLOCK button
for 5 to 10 seconds. While the UNLOCK button is being pressed, press
the PANIC button and release bothbuttons simultaneously. You will hear
a chime sound to signal you that programming on the new transmitter(s)
may occur.
3. You may program up to 4 transmitters for your vehicle within a 30
second timed window. Press and release both LOCK and UNLOCK button of
a transmitter at the same time; then press any of the buttons once,
you will hear a beep when the transmitter has been successfully
programmed. A chime will sound when the 30 seconds is over, or if you
turn the ignition off.
4. You must repeat step 3 for all transmitters that will be used with
this vehicle (up to 4 total).

When it's not below freezing out in the garage I'll give the process a
whirl.

Oh, I did find a similar process on the web, but it did not include
the step to press both LOCK and UNLOCK buttons at the same time.

John Keith

 

When all else fails RTFM! The following info was found in teh Owner's
Manual fo rthe 2000 Caravan:

1. Turn ignition switch to the ON postion and leave vehicle in park.
2. Using a previously programmed transmitter, press the UNLOCK button
for 5 to 10 seconds. While the UNLOCK button is being pressed, press
the PANIC button and release bothbuttons simultaneously. You will hear
a chime sound to signal you that programming on the new transmitter(s)
may occur.
3. You may program up to 4 transmitters for your vehicle within a 30
second timed window. Press and release both LOCK and UNLOCK button of
a transmitter at the same time; then press any of the buttons once,
you will hear a beep when the transmitter has been successfully
programmed. A chime will sound when the 30 seconds is over, or if you
turn the ignition off.
4. You must repeat step 3 for all transmitters that will be used with
this vehicle (up to 4 total).

When it's not below freezing out in the garage I'll give the process a
whirl.

Oh, I did find a similar process on the web, but it did not include
the step to press both LOCK and UNLOCK buttons at the same time.


John Keith

 

My '95 T&C and my '94 T&C are both programmed to use the same
2 key fobs, mine and my wifes.

But I have to warn you - it seems line a useful thing - but the problem
is that since both vans sit next to each other, when you click on the
rear hatch button to unlock the rear hatch, both hatches on both
vans open. Then what happens is invariably after getting the groceries
in or whatever, you forget to slam the hatch closed on the other van -
and then at 9:00pm at night your S/O looks out the window and sees
the interior light on, and you get a yelling at, and have to go out in
the cold and slam the hatch closed.

Ted

 

The RKE system and transmitter use a rolling code method for transmitting
the information . Rolling code is a method used to provide extra security to
a transmitted signal. The transmitter sends a randomly selected sequence
code each time a signal is sent. The code increments vary depending on a
unique algorithm that is preprogrammed to each transmitter at the time it
was built. The sequence changes each time the transmitter is used. ( If a
scanner is used to try to pick the signal up it can not be duplicated)
because the sequence code cannot be calculated from the encoded
transmission. The receiver module also learns the transmitter id code and
initial sequence code at the time of transmitter programming. The receiver
then expects the next transmitted sequence code to increment within a
predetermined range of numbers
Each Transmitter has its own code and the code is programmed and stored into
the receiver memory. The newer key fobs transmit a unique rolling code id
message to the RKE module. Transmitters and receivers are unique to each
vehicle line and will not work.

 

Thanks, Glenn. So, if I read that right, my two LH cars sitting in the
driveway could not be programmed to simultaneously both work with the
same remote?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

I cant see how you could defeat the system to allow it to work

 

look on the rear case of the keyfobs if the part numbers are the same it
may work

 

So far, what you're saying is that the FOB sends out a different
sequence each time it's pressed, and that the ID code of the fob can
be uniquely calculated from the transmitted data stream based on an
algorythm.

I doubt that the fob actually does generate a completely different
stream each and every time it's pressed, as I doubt that the designers
would ever anticipate someone with enough electronic gear would be
close enough to the car to (a) want to open/unlock the car without
possessing the real fob or key, (b) be close enough to evesdrop and
capture the transmission, and (c) possess the electronics required to
replicate the transmission. Just consider a use-case situation.

But even if the fob does generate a different stream each time it's
pressed, then I guess the receiver in the car would have to never
respond to the same stream twice.

Now that has got to be total bullshit.

I can see plenty of situations where the fob and receiver can get out
of sync with each other. There would be no need for this
syncronization if the fob simply generates different streams that
algorythmically always reduces to the same unique ID code.

I guess we'll have to wait and see if John Keith posts back his
results.

And by the way, do those 2 vehicles have sentry-key?

If so, would they/could they have the same physical ignition key?

 

Your right it has to be total bullshit, But it isnt, google rolling code!!
No wait, I will do it for you. http://en.wikipedia.org/wiki/Rolling_code

 

maxpower, there is nothing in this description that would preclude
the original poster from programming the same keyfob to open multiple
cars - as long as the keyfobs were the same part number AND as
long as the system didn't have a different set of pseudo random number
generators. (PRNGs)

If for example the transmitter had a table of, lets say 200 different
PRNGs, and during keyfob programming the transmitter uploaded
a selected PRNG to the keyfob, then you would have a problem
doing it. What would happen is both vehicles would likely use a
different PRNG.

But, if the PRNG's are only different between vehicle models, and
or years, and the PRNG was burned into the keyfob, then as long
as both cars used the same PRNG you could do it.

I can guarentee to you that at least up to 1995 Chrysler did in fact
use fixed PRNGs in the RKE system. In fact the sequence generator
was the same algorithim for multiple YEARS. That is why I was
able to program both my '94 and '95 van to use the same keyfobs.

They changed the remotes in 96, and I would assume the system
as well. But, if the new keyfobs are transmit-only, then it would be
very likely that keyfobs of the same part number would use the
same PRNG and would work.

Frankly the entire system is way overengineered. A thief simply
walks up to the car and smashes the window with a rock, he does
not bother fiddling around with sniffing RKE signals.

Ted

 

LOL! Kind of like when Indiana Jones proved you don't have to learn
martial arts or how to handle a machete as long as you carry a loaded
gun around with you.

Remember the saying: "Locks are for honest people". IOW - many people
would steal if something's laying out there, but a large percent of
people will, for several different reasons (laziness, some minimum level
of conscience, etc.) not steal if they have to do some conscious act
that crosses a certain line (like picking or cutting a lock or breaking
a window). IOW - adding one more layer of security will be effective to
some degree on the statistics - a certain percentage of would-be crooks
would be deterred by the over-engineered system who otherwise would go
to the trouble of obtaining and using some kind of simple code-breaking
machine (on the pre-'96 system). But yeah - there will always be the
gutsier scum who will break the window no matter what.

I complain all the time about how cars are over-engineered in some areas
these days, and that we've reached the point of diminishing returns in
some areas of technology use, but in this case, if you think about it,
the development costs of such systems are amortized over practically all
new cars on the planet (I'm assuming the algorithms and chips all come
from a handful of manufacturers), and the per-unit costs are probably
not increased much at all. IOW, there is some slight benefit overall,
but the cost is almost zero compared to a, say, pre-'96 system. It's
not like some feel-good systems that are on our cars now or in the
future from which the benefits are questionable but the added cost per
vehicle is one or more hundreds of dollars.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')