BBS SPY wrote:

Following a PM about this transponder thing i mentioned in my prior post on this thread, i thought it better to post up a bit of a better explaination here so anyoneone who is interested can read it and might benefit.

I dunno how i happen to know so much about them as i have never had any real big reason or cause to play with them although before writing diagnostic software for any system i do tend to figure out how it all works first.

Typically (dispensing with the phsicallities of the blade part and concentrating on just the electronic part(s)) modern key fobs do 2 absolutely and totally seperate jobs.

The first is to provide a remote (typically to 10 or 20 feet) radio link to the vehicles alarm / Body control with a couple of buttons to Lock and arm the vehicles alarm. This capability typically requires battery power of some form or other, a microcontroller to handle everything, buttons, a memory chip to provide individul per key data that stops other keys from unlocking the car, an RF circuit and usually an antennea track or chip. Basically a small PCB. Other buttons can be piggy backed on this to provide other remote controlled functionality. Typically there will be an antennea to an alarm or Body control ECU or a remote reciever module located in the vehicle for this and in the cae of the D3 this remote receiver module is located in the roof on the mid cross beam strenthener, about mid point in the car.

Digressing for a moment i should tell you that I once fixed a week old car for a dealer where, the car started and drove fine but would not remotely lock and unlock. Turned out one of the small bolt for the receiver module which also provided it with earth was not fully screwed in from factory. soon tightened and fixed. When later explaining the find / fix to the SM, i was stunned by the story of a mechanic who swapped the receiver out on a new Sport but somehow got the bolts mixed up and refitted a slightly longer one resulting in a nice bulging dink in the roof skin that required some serious panel beating filling and re spraying to fix.

The second job a key fob does is to mobilise the engine management. Typically there will be an Immobilizer ECU such as the EWS3D used by Freelanders and L322's (FFRR's to you) located in a very hard to reach place in the vehicle, This is connected with a data link to the engine management over which it sends rolling code info that causes the EMS to start. It is also coupled to a circular coil that is located around the face of the Ign Key barrel.
When a key is inserted and the IGN turned on, The Immobilizer ECU feeds Power to this coil which creates a field of electromagnetic energy.
This energy is picked up by a small chip in the key fob which is typically fitted as close to the key blade part of the fob as possible, has no legs and really just looks like a broken bit of plastic.
http://www.askthemechanic.co.uk/images/Slideshow2.jpg
These chips (generally referred to as transponders) are industry standard and some even contain programmable memory.

The electromagnatic energy is enough to power them and they then transmit data at a frequency that is picked up by the coil and relayed to the Immobilizer ECU which can then transmit back to the transponderif required but ultimately its job is to validate the transponders presence and allow the engine to start.

Most often the transponder and radio bits are fitted in the same key fob as it is in my 2003 L322 Key / fob. but the fact that they are seperate elements is shown by the fact that for a new key i would have to learn the fob to the Body control so it locks and unlocks the doors and then diagnostically tell the EWS3D ecu to accept a new key so the engine will start. however a 2001 on freelander has the transponder in the Key but the door / Alarm bit is a seperate fob.


In the case of the Disco 3, things are a bit different and it is only due to my having such detailed and prior understanding of what i have just explained that i am so interested and intrigued to note that there is a space specifically designed in the casing specifically for an industry standard transponder chip that is not used. Perhaps a back up plan

As such i can only conclude that the 2 elements have been sucessfully combined and in the process the electromagnetic power picked up from the coil is now used to chage the fobs battery.

As such all memory for both functions must reside in the single on board micro controller located between the two primary buttons.

In addition, although a new fob can be learned to any vehicle, once learned it cannot then be re learned to another, so something is stored in the key fob.

wiggs wrote:

Great news

Very happy at the moment
Having a cheap LR period for a change.
Cheap new keyfob and a new vacuum brake system under warranty