Lucas 10AS remote fob re-sync

Why are all jobs on cars more complicated than you expect.

All I wanted to do was pickup some power behind the dash in a 1998 300TDi Land Rover Defender 90 and I ended up having to learn how to re-synchronise the immobiliser remotes.

In order to tap in to a permanent feed I had the power to the factory standard Lucas 10AS alarm system removed for perhaps 2 hours. By the time I put it all together again the remotes had decided not to disable the immobiliser.

Lucas two button remote

I went on to the Internet to find out what I should have done when disconnecting the battery. It did not take long to find out that I did not have to do anything in advance but that it was now necessary to re-sync the remotes to the alarm system.

Easy, they say, just press the lock button four times quickly in a row and they will work again. WRONG, that is only partially correct for our Land Rover.

After a lot of frustrating trial and error and snippets of information from various sources the following is what worked for me to get the remotes working again on a 1998 Defender, that does not have central door locking:

1. Shut all the doors and the bonnet of the Defender. I left the doors unlocked.
2. Take the remotes away from the car (I don't know if this is necessary)
3. Open a remote
4. Remove the battery from the remote
5. Press the buttons to discharge any residual power (I don't know if this is necessary)
6. Put the battery back in to the remote
7. Go back to the car but do NOT open the doors (I don't know if this matters)
8. From outside the car. Hold the remote a few inches from the windscreen facing the steering wheel
9. Press the UNLOCK button 4 or more times fairly quickly in a row

All being well the indicator lamps on the dash should flash to show that the immobiliser has been disabled. The remote should now work as expected.

I repeated this with the other remote and now both my remotes work.

One other thing that might help. To open the remote fob, remove it from the key ring and use a small screwdriver or blade at the key ring end, slide it in to the thin slit and twist to separate the two halves of the fob.

I had investigated bypassing the immobiliser, just in case all else had failed, so I now know a lot more about that than I previously did.

On the internet, people claim you can bypass the immobiliser be replacing the 'spider' box that is  deliberately well secured in the end of the battery box. The security is better than that, not much but a little. Some of the immobiliser functions are within the Alarm ECU, so unless you want to re-wire part of the car, getting the remotes working is the easier solution.

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