Hi!

I am intrigued by the security used in the Jaguar key and key fob for
the 1999 XJ8. So, I looked up the security chip info used by the car
manufacturers.

Basically there is a tiny security code integrated circuit chip (eeprom)
embedded in the plastic/rubber handle of the key. It is a passive electronics
device that uses the RF energy emitted by the car security transponder reader
to power the circuit.
It is very similar to the RFID tags used by stores for theft protection (Loss
Control ?).
This security chip is read by the security reader module in the steering column.
It has an antenna that is in the plastic/rubber ring around the ignition key
slot in the steering column.

When the key is placed in the ignition and the key is rotated to the "Start"
position the security reader reads the code in the security chip on the key.
This is why you DO NOT want the other keys near the steering column
when you are starting the car or programming the key fobs.
The reader can pickup other key security codes if they are too close to the
Ignition Switch and get confused and possibly placing the car in the
"Immobilized" "NoStart" mode.

Each key has a security chip with a different code. Over 100+ million combinations are possible.

The Jaguar XJ8 can have up to 2 Master keys and and 1 Valet key programmed
into the ECU (Engine Control Unit).
I have found some interesting bypass procedures where you can remove the
chip from a Master key and glue/tape it directly to the Ignition ring and
thereby use a non-chipped key(s) to start the car.
Other processes use a bypass module to send a Start signal directly to the
ECU.

I found this YouTube video showing how to program your own keys using
a computer with a RS-232 serial port.
WARNING !! This is for the seriously experienced electronics tech !!
You could turn your ECU/ECm into a brick if you are not careful or
knowledgeable.


This tech was using a Toyota ECU/ECM to reprogram the key security info.
Apparently the Toyota ECU/ECM will read the new key security codes from the
keys and write them into the ECU/ECM eprom chip if the old codes in the
eeprom chip are zeroed out using the eprom edit software.

I haven't found any info on using the Toyota programming method on a
Jaguar XJ8 ECU/ECM. Yet.

Regards and POR - Press On Regardless

 

If you've got at least one working chipped key, it would be much easier to clone the existing rfid code to a new passive rfid tag than to reprogram the car for a new code.

Any rfid reader should be able to get the code off the key, then any programmable rfid tag can be programmed with that same number.

 

Afaik, our cars cannot identify valet keys through the electronic rfid/security system, I've converted my valet key into an additional master by shaving down the metal wings and there is no difference, the car will activate/deactivate valet mode with any of my keys now.

 

The car can be configured to accept up to 5 keys (master or valet, it does NOT matter)

bob

 

HI!

Okay, I was curious when I read the programming procedure and it stated
"2 masters and 1 Valet" key.

Apparently it was referencing the new car owner receiving
"2 Master keys and 1 Valet key" from the dealer at the sale.
The keyfob programming method allows for 5 keyfobs.
Which would mean up to 5 separate keys could be used.
All the keys will have the same key cuts (Valet Key is slightly different)
but will have a different eeprom security chip in each key handle.

I am still investigating how the remote fobs are validated by the car security
system. It apparently uses a different reader than the one in the steering
column ignition switch.
The ignition switch key reader is only enabled when the key is turned to the
"Start/Ignition" position.

When using the remote fob, it is not anywhere near the ignition switch yet
and does not require the car to be in a "Start/Ignition" mode.
The remote fob radio signal seems to be read and decoded by the
"Security" module in the trunk.
The 98-2000 key fobs use a 315MHZ key transmitter.
The key fob transmits a security code embedded in the key fob that doesn't
appear to be changeable. Each fob has its own security code programmed by
the manufacturer during the manufacturing process.
This code is stored by the security system during the key fob recognition
initialization procedure into the security module in the car trunk.
This code is recognized by the security module and allows the function
sent by the keyfob to be implemented:

Lock, Unlock, Headlight flash and Trunk open.

If a keyfob fails to work, go to one of the auto parts store and test the keyfob
transmitter.
Most of the parts stores have a keyfob tester that you can use for free.
Sometimes the conductive coating on the keyfob keypads is worn off.
You can either replace the keyfob ($$$)or you can repair the keypads.
There are some kits that paint another conductive coat on the keypads
and others that glue a flexible metal disk on the keypads.
I saw a couple of different kits via Amazon and eBay for $6 -$20.
Or it could be the CR2016 batteries. Each 1999 XJ8 Keyfob uses
2 of the CR2016 batteries. They do run down over a 2 year period.
Cost seems to be around $6 for pack of 2 batteries.

Regards and POR - Press On Regardless.