Key help!

[CMGRover]

My main key works only to start, and on occasion, it will work normally. Spare key works just as intended. No "Low battery" messages at all. Really stumped. I'm thinking possibly the transponder coil, as maybe the key isn't getting a charge? Therefore, I don't want to use the spare, as I don't want to deplete the charge on it.


Thanks for any help!

 

[bbyer]

How to replace the battery.

Well the ten year life rechargeable battery appears to last maybe five years. As such, below are instructions as to how to get at and replace the battery.

http://www.**************/forum/topic39609.html?highlight=+key++fob

Replace the **** with disco3 co uk with periods where the spaces are.

The internal design of the key fob circuits is such that there are effectively two independent circuits: the door lock unlock pushbutton business that is powered by the "rechargeable" battery and the engine start or not function, that is powered by a pulse from the engine computer and hence is not battery state related.

What this means is that you may not be able to get into your 3, but if you could, it would start. In short this means you had best exercise the manual mechanical key hole to make certain that the mechanism is not frozen from lack of use.

It is of course possible that the battery recharge mechanism is not working but I do not know of any simple way to determine that. I would expect it is OK and that the problem is the battery within the key fob as that is common.

I suppose the only way to know is to run the second key and if in a months time, all seems well, then you may as well tear the non working fob apart and change out the battery. In the meantime, as I said, make certain you can get in mechanically.

 

[CMGRover]

Thanks so much. I'll run the spare set for a bit, see what that does. The manual entry is fine, it's been getting used quite a bit recently...

 

[bbyer]

One other thought re the engine start.

Above I said that the engine start permission does not require battery power from the key fob battery. I think I am correct in that, however there is a contrary view that says the engine start allow circuity within the key fob does need power from the key fob battery.

If you wish to experiment, continue to use the dead key for engine start and see if it keeps allowing start. Also the second key can apparently be charged by either taping or with an elastic band, the key fobs together. The charge field, (as with an electric tooth brush), extends out about 3/4" from the ignition coil so a second nearby key will apparently charge - not pretty but if the charge circuit works, then the second key can be topped up.

The start not start permissions are stored within the CJB printed circuit board and that is why when it goes, it has to be programmed back to the particular vehicle VIN. The actual CCF, Car Configuration File, is however stored or backed up within the Instrument panel pcb so that the new CJB pcb knows where to find its new old data. That in part explains why both are so expensive - both are variations of computers probably running UNIX.

It is good to hear you know of the alternate entry mechanism and that it works.

If you end up purchasing a new key, you can tie the non working one underneath somewhere and you will have your own valet key.

 

[hell pie]

I was having a similar issue a while back where one of my key fobs would start the vehicle without any problems, but was intermittent with locking/unlocking the doors. I opened the fob and upon close examination I discovered that one of the leads soldering the battery to the circuit board had come undone. I suspect this was because of one too many drops onto the ground. I resoldered the lead and the fob has worked flawlessly since.

 

[bbyer]

The solder solution may be more common than one thinks.

I was having a similar issue a while back where one of my key fobs would start the vehicle without any problems, but was intermittent with locking/unlocking the doors. I opened the fob and upon close examination I discovered that one of the leads soldering the battery to the circuit board had come undone. I suspect this was because of one too many drops onto the ground. I re soldered the lead and the fob has worked flawlessly since.

You may be being kind to LR. I have heard of others saying they also had to re-solder a battery wire inside so perhaps there is a history of weak solder joints and that accounts for the apparent dead battery behaviour.

It seems over time with these forums, we do determine what the problems are and also the solutions.

I understand that on the newer vehicles that either they do not have a key at all or the battery is now the older style throw away non rechargeable. I think sometimes Land Rover gets too far ahead with the new technology thing - almost like they are the introducer of any new idea and we are the testing department. My wife has the same style switch knife key fob for her VW Passat, but it has a replaceable battery. I have yet to replace the battery and it is ongoing five years now. My GM remote seemed to run years as well with no battery replacement needed.

Maybe the LR key fob sends out such a complicated pulse signal to the door lock receiver that the transmitter inside has the power requirements of the WWV time signal transmitters, hence the constant recharge requirement?

 

[CMGRover]

Good info...keep it coming! I need to rip into the fob, check the solder....