 | Home > Puma (Tdci) > Key fobs not unlocking or disarming alarm/immobiliser |
 
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| s55shh Member Since: 30 Dec 2019 Location: staffs Posts: 193  
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It sounds like your key fobs have become unpaired. Are they the newer type with the silver strip down the sides?
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21st Jan 2021 7:36pm |
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| glpinxit Member Since: 31 Jul 2010 Location: rural Somerset Posts: 156
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Yes, two buttons, black rubberised jobbies. And the ‘silver strip’ which holds the black halves together slides and is removed to allow the halves to be separated so that the battery can be accessed.
Is ‘becoming unpaired’ common? If so is there a known cause. Cheers, Guy. |
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21st Jan 2021 7:54pm |
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| s55shh Member Since: 30 Dec 2019 Location: staffs Posts: 193
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OK, my 2011 became unpaired due to flat battery issues and there is a repairing method involving standing outside and repeatedly (usually 4 times) pressing the lock button until the indicators flash, then press unlock.
My 2015 had the later type keys and a similar incident caused the central locking to still work, but immobiliser locked on. No re-pairing possible, new ALM unit and keys £800 please. Its possible that someone with a decent scan tool might have a chance with yours. Otherwise, look at remotekey.co.uk for other options. |
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21st Jan 2021 8:45pm |
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| macfrank Member Since: 05 Nov 2015 Location: somewhere in the north Posts: 1076  
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My spare fob didn't work after not being used for a few months. It's normal in this case.
Car remotes use a 'rolling code': when you press a button on the key fob, a code is transmitted and the car's ECU checks if the code is correct and opens the door. If this code would always be the same, it would be too easy to copy. So, after a button press, both fob and car select a new code from a list. They both have the same list (it's actually a cryptographic algorithm, making it impossible to predict the next code). So if you press the button next time, a different code is sent, but the car has the same from its (same) list - doors open. If you press the fob when away from the car, the fob selects a new code from the list, but the car can't follow. Or with my spare: my main key and the Defender were way ahead in the list, so the spare was out of sync. They won't get out of sync, however, by pressing the fob just a few times. In case the ECU receives an incorrect code, it looks ahead in the list and compares the next, say 100 codes or so (don't know the actual figure, probably 255). I just had to press "lock" four times as described in the manual under "key fob battery replacement". |
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21st Jan 2021 9:05pm |
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| glpinxit Member Since: 31 Jul 2010 Location: rural Somerset Posts: 156
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Update-
Yesterday morning and I tried a pessimistic press on the unlock button and it unlocked (and locked) and started too! The spare fob and key did as well. So I went out to buy bacon rolls for breakfast. Later we went out to the supermarket for the weekly shop after which the fault returned leaving us stranded in the car park. Should have taken the hint I suppose. The RAC recovered me the mile and a half home but that took four and a half hours. They have a new ‘process’ for key and electronic problems. This entails sending out a specialist whose role seems to be to turn up, check that the fobs are transmitting a signal, looking the vehicle up on their ‘knowledge base’ and concluding that it can’t be fixed so back to the RAC to recover the vehicle. Apparently the knowledge looked up says that the immobiliser unit has to be replaced. This ‘process’ took two hours. When he arrived an hour later the RAC patrol man decided that he couldn’t tow me (combination of weight and tight turns in the carpark) but luckily the RAC had already despatched a recovery truck with a sliding tray on the back. While we were waiting for that he was determined to disconnect the battery so after I had read on here the night before how to ensure the BBUS didn’t go off he did. That didn’t work of course but he wryly commented that his experience of Defender and motor bike owners was that they usually knew more about the problem than he does. If someone can tell that to RAC HQ then that will save me time and them money in future. Now I’m back to waiting for the security number to arrive so I can disable the alarm/immobiliser, working out whether to replace like with like or get a different alarm/immobiliser fitted. Cheers, Guy. |
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23rd Jan 2021 9:17am |
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| Mdm Member Since: 11 Sep 2013 Location: Sunny Lancashire Posts: 1599
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its a common fault and worse since lock down
car battery being flat causes it as well. the ecu are not as reliable as the old green ones which are obsolete now as well as the older black box ones im told. sometimes a workshop can reteach the fobs to the car otherwise its a new alarm ecu and code the fobs you can get the ecu tested and repaired and my neighbour has done that after he left his 90 flat for 6 weeks over lock down.. he now has a trickle charger..... |
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23rd Jan 2021 6:34pm |
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| Julie Member Since: 07 Oct 2017 Location: Nantes Posts: 484 
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Other signals may be transmitted on the same frequency causing problems on your car's ECU JLR did not reserve a private frequency i.e. anybody may interfer your fob's communication Once, I had this problem on a road trip nearby a restaurant. Many people around. Impossible to determine thé cause. I just waited a few minutes while smoking a cigarette. Then it worked perfectly. No issues ever since |
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23rd Jan 2021 7:14pm |
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| s55shh Member Since: 30 Dec 2019 Location: staffs Posts: 193
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My EKA code didn't work either. I ended up getting assistance from remotekey.co.uk
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23rd Jan 2021 9:37pm |
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| steve E Member Since: 06 Mar 2011 Location: Tenby Posts: 2073 
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In the cold weather l have to unlock, lock then unlock again to get it open properly
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23rd Jan 2021 10:34pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17383 
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They couldn't even if they wanted to, that's not how the allocations of frequencies in our congested bandwidth work, all car security systems in the EEC use the same narrow band. Unfortunately there are other radio systems which use adjacent bands and can cause interference, and there is a limitless supply of interference sources as well. Not long after I bought my Disco2 it became completely impossible to lock or unlock it when it was parked on my drive, but if I pushed it 20 feet onto the road it was fine. It was just about the time that the Dorset Police Tetra network was being commissioned, and in the end I concluded (after borrowing various bits of test equipment from work) that there was a nearby Tetra cell with a fault. I phoned Hutchison, the telecomms firm building the network, who said that my suggestion was ridiculous and it couldn't possibly be one of their cells, but strangely within 3 hours the problem went away and has never come back. Draw your own conclusions. Remember also that the more sensitive the receiver, the more likely it is to pick up interference. The very popular key range extension modification, which so many of us do, can actually make the vehicle more susceptible to interference problems. |
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23rd Jan 2021 11:28pm |
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| rockster57 Member Since: 15 Nov 2014 Location: West Yorkshire Posts: 937 
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If the remote battery needs replacing, it’s not just a case of prising apart and popping a new one in. Not sure if they’re all the same but on my 2011MY before the battery swap i have to turn the ignition key to position II, turn off, remove key, then do the lock button press from the outside. Takes a minimum of 4 presses before the fob pairs.
You get various different warnings that the remote battery will soon be due for replacement:- Remote will only work with 2nd press of unlock button, Indicators will not flash when alarm disarmed Alarm indicator in dash continues to flash rapidly after the initial 10 second period of rapid flashing It’s all in the Owner’s Handbook |
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24th Jan 2021 12:21pm |
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| discomog Member Since: 09 May 2015 Location: Notts/Lincs Border Posts: 2526 
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Unbeknown to me SWMBO had a problem with the key fob on her Discovery Sport (Same fob as late Defenders) in that she could not unlock the doors so she put it away in our key safe and used the other fob for a couple of months until that had the same problem. I opened up both key fobs and checked the battery voltages, both were reading just above 3v dc so decided that the problem lay elsewhere. (Admittedly this was an open circuit test but I still would have expected to see a reading less than 3.0)
I had two new Duracell CR2032 batteries so decided on the off chance to just to give them a try. Low and behold both the fobs were back working with brand new batteries. Morale of the story - don't be fooled into thinking that a correct open circuit voltage reading on this type of battery is an indication of a good battery. Defender 90XS SW Mini Countryman Cooper S Morgan Plus 8 |
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24th Jan 2021 2:04pm |
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| s55shh Member Since: 30 Dec 2019 Location: staffs Posts: 193
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we used to have Dolphin Tetra Band radios at work and one of them would reliably unlock our Astravan with a Clifford alarm.
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24th Jan 2021 3:32pm |
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| Bish Member Since: 11 Nov 2008 Location: Hungerford Posts: 428 
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Give Ian a call at remote key.
https://remotekey.co.uk/ He will reset the black box that controls the alarm functions (or green depending on age of vehicle) and reprogramme the keys. He is very good and knows all there is to know about these alarm systems. Thanks Bish |
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25th Jan 2021 1:43pm |
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