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Having a bit of a nightmare.

I have just unlocked the car, got in a few minutes later and as I went to put the key in the alarm went off.

No response from the key fob.

The alarm continued for a minute or two, changed its song & then stopped as soon as I put the key in the ignition.

It is now completely dead as if there is no battery connected at all.

There is history to this.

The problem happened last week, called the RAC out who said I had a dead battery in the fob,

we changed it, played about for a few minutes trying yhr unlock/lock and suddenly all started working again.

Any thoughts please.

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As it was behavig like there was no battery I gave it no battery.

I disconnected the battery, reconnected & magically all appears to be OK.

I am guessing the immobiliser kicked in and shut down the whole car.

Would going through the emergency key access procedure have sorted this ?

And is there another problem or is it to do with the fact that I unlocked the car and then went away for a few minutes.

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  • 2 weeks later...

the Td5 immobiliser is the same as a late Tdi300. it uses the 10AS unit.

The Tdi uses the Spider while the Td5 uses the MEMS/Td5 - ECU.

when you changed the battery in the fob and pressed the lock and unlock repeatedly (accidentally, you were actually 'resyncing' the fob to the 10as, as you happen to get the sequence right by chance).

The correct way to resync is, take out the battery in the fob, press both buttons a few time (drain any current left), then fit the battery. Next you press the lock button 4 times and then the unlock once, it will resync. (mind you, the car must be not armed)

in the 10AS, there's an option about 'time sync'. enabled by default, this is part of the sequence for verifing the rolling code to disarm and unlock the doors (CDL if fitted). so even if someone know the rolling code, you will still need to be 'in sync' with the 10AS before the system will disarm (and unlock).

this provides added protection for your defender (free lander 1 / disco 1 / 2).

you can set an option called plip resync either when disarm or arm. this puts the two in sync when you do either action. by default, i believe it's resync on disarm.

there's another time difference option (can't remember what it was called) but when enabled, it allows the two to be 'out of sync' up to 9 seconds on the hour. this is set enabled by default.


so having said all that, when the fob is off sync, it doesn't allow you to do anything and if you keep pressing the fob it will detect it as a bad fob, ie correct rolling code, but still not quite right. so there's another setting in the 10AS called 'bad plip allowances', usually set to 4. so the alarm rings when it receives a 'bad fob' signal after that 4 attempts.


now, how to avoid this situation again. if your plip battery is low, it should be indicated with 2 flashes on the red led (speedo) instead of the single flash per second. there's another option in the 10AS where you can set number of times the 10AS receives a low battery status from the fob before the above happens. this is usually set to 10.


the EKA code allows for the vehicle to be driven but it has to be entered everytime the vehicle is to be started. you can find the procedure in the owner's manual or workshop manual. it's the open / close door / turn key sequence.

no, leaving the car unlocked (door open) only reactivates the passive immob after 5 minutes. there's another option in the 10AS to relock the doors and rearm if you pressed the unlock on the plip and didn't open the door after 1 minute. not enabled by default.

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Thanks 'Old Hand', very detailed.

My problem disappeared & has now come back with a vengence,

One really odd thing is that it is intermittent. The fob/central locking all works for a few days & then stops for a 30 minutes or so & then is happy again.

For the first time 2 days ago it packed in while driving. The alarm came on & the vehicle went completely dead (just like no battery fitted). I a managed to coast it to safety thank goodness.

To me this sounds like something other than what you have described Old Hand. What do you think ?

Possibly a dodgy connection/bad earth.

It is with a garage at the moment but they are not sure what to do & the bill is mounting up.

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  • 3 months later...

My apologies, i haven't been reading the forum lately.

I hope you have sorted out your issue.

If you do have access to a nanocom, perhaps you can read the settings once first and save the file. (most important step, as things can go seriously wrong when you get an incorrect setting and your truck is immobilized far away from home, ask me how i know)

next put the alarm into learn ECU mode. this will take about 1 minute for it to try to query the ECU and learn its codes. there are times in which the 10AS can be mobilised but the ECU stay immobilised. this will allow cranking, but not starting. no red light on the speedo either.

when you mentioned the alarm comes on, does it sound the horn or the BBUS (battery backed up sounder)?

If it sounds the BBUS, it could be an earth fault as when the 10AS is 'disconnected' so immediately the BBUS is activated as it thinks the truck has its battery disconnected and the ECU will go into immobilised, hence killing the engine immediately.

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  • 3 months later...

A bit late but thought I would follow up on this.

It turned out my issue was with my battery.

One of the pillars was 'wobbly' causing an intermittent issue mainly affecting the alarm/immobiliser which clearly did not like being disconnected.

Understandably as I guess it thought it was being nicked.

Anyway, a good few £££s investigation and a eventually a new battery sorted it out.

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