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Thread: Explanation of the reasons for the keyfob re-sync steps

  1. #1
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    Explanation of the reasons for the keyfob re-sync steps

    Winter was approaching here in the great south land and all old batteries were dying. Our daughter's Toyota Rav 4, my partner's VW Golf and my L322 remote key fobs all quit within a week. All 3 use the same battery - 20mm diameter, 1.6mm thick, 3.4 volt (nominal) lithium cell - aka 2016 coin cell. The Rav and VW retained settings during change over, but not the Range Rover. So, on to the wiki to read the re-sync instructions. After failing a few times I did some research and here is the result -

    L322 Keys have 3 lock systems
    1 - The mechanical match of the cut will release the tumblers in the driver side door and the ignition lock.
    2 - Detecting (within ~30mm) a valid Radio Frequency IDentity (RFID) chip embedded in a key will release the ignition lock latch.
    3 - A 433MHz wireless transmitter in each key fob will send codes to the Body Control Module (BCM).
    While most of the world uses 433MHz for remote unlocking the US uses 315MHz ...

    The mechanical key cut is easy to defeat. That is why the Radio Frequency IDentity system was added.
    A set of RFIDs (8-10) is stored in the BCM at the factory. The first 2 match the chips inside the keys initially supplied, and only Range Rover keeps a copy of the other codes. Replacement keys need a valid RFID chip inside, either physically moved from the old key or supplied (by Range Rover) on purchase of additional keys.
    However a tech savvy locksmith can overwrite codes stored in the BCM to match new RFIDs. For a large fee. Why? Because the BCM has to be taken from under the left seat to the locksmiths electronics workshop, pulled apart, the memory chip accessed with an in-circuit clamp and ... so on.

    Besides the RFID # the Body Control Module also stores a list of valid key fob transmitter IDs and calculates a new access code for each fob every time it receives a key press message from that fob. All remote key fobs also calculate the same new access code (unique to themselves) ready for the next key press. The remote may be pressed when out of range so that its calculated code may get 'out of sync' with the access codes that the BCM calculates.
    To accommodate this the BCM always calculates ~100 concecutive new access codes and accepts them all. It then re-adjusts to a matching access code so that it stays 'in sync' with each key fob.

    But sometimes the key fob will get more than 100 codes out of sync. This can happen when a grand kid plays with your keys or the battery goes flat and the key fob 'forgets' the current code (or re-boots to start from some default value). Also a drowned or corroded (destroyed) transmitter may also be replaced with a new one. In each case the BCM can still be re-synced to the key fob's current access code by sending a special sequence of button presses from the fob. BUT the re-sync re-writes the entire key fob data table, so all existing keys need to be re-synced whenever this procedure is done.


    Step 1 - setup 'standard conditions'
    Key operator in driver's seat
    All doors closed
    All doors un-locked

    Step 2 - initialize BCM to re-sync mode
    Put a valid key into ignition lock
    Turn key to I (accessories) - this can only happen if the key's RFID is stored in the BCM
    Turn key to 0 (off) within 5 seconds (any longer cancels re-sync mode)
    Remove key from ignition lock

    Step 3 - send re-sync sequence
    Hold key at face level (receive antenna is at this height)
    Hold down un-lock button, wait till send LED flashes at least twice
    Press and release lock button 3 times
    If successful all doors will lock then unlock.
    Both the transmitter ID and the new (next) access code are stored in the BCM's temporary memory.
    Release un-lock button too

    Repeat Step 3 for every key fob. Step 3 has a time limit of 30s per key. Over-running any timeout
    will part cancel re-sync mode. Remember, ALL keys need to re-sync in the one procedure, 30s each -
    if any key fails to sync go back and do step 2 twice (once to fully cancel re-sync mode and once to
    re-start it) then steps 3 & 4. Missed keys will be waaaay out of sync.

    Step 4 - write changes to BCM permanent memory
    Put the key (that was used to start the session) into ignition lock (MUST be same RFID as Step 2)
    Turn key to I (accessories) - this must be done before the last Step 3 30s times out.
    Turn key to 0 (off)
    Remove key from ignition lock
    All done. Test all keys.

    Note - badly worn conductive contacts or plastic buttons on a key fob can cause the re-sync to fail because they don't make contact, or prematurely release a button, or send multiple presses for one user press, etc. This was where my problem was, but a little bit of "shoe glue" applied to certain points inside the key fob plastic buttons restored clean, clear key presses and the key synced first time.
    Besides the plastic button wearing the actual conductive coating that the button presses against the circuit board also wears away over time. There is very little you can do to fix this except by replacing it. The good news is that a replacement plastic sheet with a new conductive contact dimple is included with most ebay button and fob kits.

    Note - a key without a RFID chip is still able to unlock the door, but can't start the engine. Useful if the 'real' key accidentally gets locked in.

    By-the-way the RFID chip in the key is used by the BCM for all the other luxury touches like individual seat position, outside mirror positions, gear changing preferences, etc.

    bye.
    Last edited by p38arover; 12th October 2019 at 10:54 AM.

  2. #2
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    Thanks for that You should also post that on the Ffrr site

    Laurie
    Last edited by p38arover; 12th October 2019 at 10:53 AM.

  3. #3
    p38arover's Avatar
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    Quote Originally Posted by bgennette View Post
    Hold key at face level (receive antenna is at this height)
    The workshop manual says the receiver is in the tailgate but some say it's in the door pillar. It looks like it's in the tailgate. I wish the panel came off this easily:



    I'm tempted to take it off again (I had it off 2 weeks back to replace the high level stop light) to check the receiver for corrosion.
    Last edited by p38arover; 12th October 2019 at 11:02 AM.
    Ron B.
    VK2OTC

    2004 L322 Range Rover Vogue 4.4 V8 Auto
    2007 Yamaha XJR1300
    Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA



    RIP Bucko - Riding on Forever

  4. #4
    p38arover's Avatar
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    My L322 battery went flat on the weekend. I cannot get my fobs to re-sync.

    I don't know why they lost sync, I've disconnected the battery many times in the past.
    Last edited by p38arover; 12th October 2019 at 11:01 AM.
    Ron B.
    VK2OTC

    2004 L322 Range Rover Vogue 4.4 V8 Auto
    2007 Yamaha XJR1300
    Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA



    RIP Bucko - Riding on Forever

  5. #5
    p38arover's Avatar
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    I found my fob would open the tailgate but not the doors. Also the central lock button on the dash is inoperative.

    A search on YouTube found this:



    Regrettably, this didn't work either.
    Ron B.
    VK2OTC

    2004 L322 Range Rover Vogue 4.4 V8 Auto
    2007 Yamaha XJR1300
    Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA



    RIP Bucko - Riding on Forever

  6. #6
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    LR Exec to engineering: "What can you come up with which will make sure that all those RR owners always have to come back to our dealers to fix their key fobs?"

    Mike
    My car: Fuji White MY13 D4 SDV6 SE 3.0 Litre, 8 spd auto.
    Wife's car: Series 2a, LWB, ex. mil., 1966. To be restored.

  7. #7
    p38arover's Avatar
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    I tried checking for faults with the GAP IID tool but found nothing. Yesterday, I borrowed an AutoLogic diagnostic computer but, after selecting key fob resync, it noted it wasn't a diagnostic function. It gave exactly the same procedure I've been using.

    When it stops raining, I think I'll have a look with my T4 and my Rovacom Faultmate (which does a lot more than T4).
    Ron B.
    VK2OTC

    2004 L322 Range Rover Vogue 4.4 V8 Auto
    2007 Yamaha XJR1300
    Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA



    RIP Bucko - Riding on Forever

  8. #8
    p38arover's Avatar
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    Quote Originally Posted by Laurie View Post
    Thanks for that You should also post that on the Ffrr site

    Laurie
    He did.
    Ron B.
    VK2OTC

    2004 L322 Range Rover Vogue 4.4 V8 Auto
    2007 Yamaha XJR1300
    Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA



    RIP Bucko - Riding on Forever

  9. #9
    p38arover's Avatar
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    Something I hadn't mentioned because I didn't think it was related was that, after switching off the interior lights whilst camping, I couldn't get them to come back on.

    I was searching FullFatRR.com for suggestions on the lighting issue and came across a suggestion to check if the car was in Transport Mode. I recalled seeing some weeks back a message in the Message Centre that the car was in Transport Mode but it didn't seem to affect anything.

    I checked with my GAP IID Tool (as it was in the car and thus convenient), trying setting it to and removing it from Transport Mode (TM) but to no avail.

    Today, I brought out the big guns and put my Rovacom Faultmate on it and found it had a TM fault registered. It wouldn't clear so I did a bit more looking and found I had to take it out of TM then clear the faults.

    Once I had done that, the interior lights worked again.

    So I thought I'd try re-synching the keyfobs. Voila! It worked. It's good to have remote locking back again.

    Thanks to vaz on FFRR for the suggestion to look at Transport Mode.

    While the Faultmate is connected I might as well run through all the ECUs and check for logged faults (and clear them).
    Ron B.
    VK2OTC

    2004 L322 Range Rover Vogue 4.4 V8 Auto
    2007 Yamaha XJR1300
    Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA



    RIP Bucko - Riding on Forever

  10. #10
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    And all that BS is why I refuse to buy an electronic car and will stick with my totally mechanical 110 County-Isuzu.
    URSUSMAJOR

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