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Discussion Starter · #1 ·
Having just fitted new rear air bag - thanks for your help on that! - I find my beloved Beast has developed another fault. It's a bit odd. When I turn the ignition key the alarm sounds. If I start the engine, the alarm goes off after five seconds.

I have a Nanocom, and had previously disabled the immobiliser. Both key fobs bring up 'Battery low' indicator even when I fitted new batteries.

I am a bit worried that if I start trying different 'solutions' I'll make the thing worse. At least at the moment I can drive the Beast.

Any ideas welcome. :shock:
 

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Well, you could unplug the siren :)
On the wild ideas front, do the electrical tests in the sticky. Perhaps low battery voltage/ system voltage is causing a problem, hence once the alternator sticks some volts into the system, the voltage comes up.
Unless you've done something REALLY clever with the Nano, which no-one else has managed, you haven't disabled the immobiliser- just part of it. The ECU will still need the correct code from the BECM before it will allow the engine to run.

You can deactivate the alarm or the immobiliser but you cannot deactivate the door switch mechanism.

Alarm deactivated= no alarm sounder.
Immobiliser deactivated= key unlock on drivers door to start
If your door switch fails, you're in a dark place!
 

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Discussion Starter · #3 ·
THanks - that sounds logical. It was parked up for the best part of two months before I sorted out the rear air bags, then got a run of about 30 miles, and left a couple of days. Perhaps the battery has gone a bit flat and the short run didn't recharge it enough. Will check the voltages.

Is it a good idea to deactivate the immobiliser - it seemed so to me as I am much more worried that the Beast will refuse to start for me than for a (presumably mad) thief.
 

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If it's a GEMS you can completely remove the immobiliser function with a suitably remapped ECU or bypass box. On a Diesel (which IIRC yours is), I've no idea.
As to whether it's worth it, if you can eliminate any requirement for a BECM signal to ECU, then I think so. Half solutions carry their own risks.
 

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Discussion Starter · #5 ·
Yes, mine is a diesel. What I find strange is that I have used the Nanocom to deactivate both alarm and immobiliser. That doesn't stop the alarm sounding when I turn the key, and switching off about five-ten seconds after the engine starts.

If I could find a way to avoid the requirement for a BECM signal to ECU, as you say, I would use it.
 

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Maybe the Nano sets BECM to send a mobilise high output to ECU at all times. If not, in theory it should be easy enough to find the relevant ECU pin, measure the triggering voltage and duplicate it, thus bypassing BECM input into the process completely.
See extract from RAVE:

Engine Immobilisation (Diesel)
The electronic engine immobilisation feature fitted to
the diesel engine derivatives is different to the
system fitted to the petrol versions.
The BeCM mobilises the engine by holding the
engine mobilise output high. The output will be low
when the engine is immobilised.
 

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Maybe the Nano sets BECM to send a mobilise high output to ECU at all times. If not, in theory it should be easy enough to find the relevant ECU pin, measure the triggering voltage and duplicate it, thus bypassing BECM input into the process completely.
See extract from RAVE:

Engine Immobilisation (Diesel)
The electronic engine immobilisation feature fitted to
the diesel engine derivatives is different to the
system fitted to the petrol versions.
The BeCM mobilises the engine by holding the
engine mobilise output high. The output will be low
when the engine is immobilised.
Ish... it isn't quite as simple as that in the end - as the BECM sends a pulsed voltage which 'transmits' the immobiliser code to the engine ECU. when I read up on it ages ago, I seem to remember reading something about the differences in immobilisation strategy - where the GEMS model it transmits the code once, and the GEMS ECU the signals the BECM if it's accepted the code (by turning on the check engine light again). Whereas the diesel models (definitely the 'late' EDC, not 100% sure on the 'Early EDC', and the later Motronic systems the BECM constantly transmits the immobilisation code - which is what would measure as 'high' on a multimeter. I don't think you can just bridge it to 'high/+5v or +12V (depending on what it uses as high) and have it run properly.

As you say, you can get a box to bypass the GEMS immobiliser in the ECU, so it will start/run any time you turn the key. There is a way of making the EDC ECU run without the immobiliser aswell, but it involves reprogramming one of the chips in the EDC ECU itself. On the diesels it's called 'Robust' mode, and can only be set during programming on a brand new ECU (basically it's either programmed with an immobiliser code, or told it doesn't need one - and this isn't changeable with standard diagnostics after initial programming from what I've read).

You could use an oscilloscope on the wire between the BECM and engine ECU and see how it transmits the code (my guess is a 12V square wave pulses at specific intervals that make up the digits of the immobiliser code or something along those lines) and then use something like an arduino or other microcontroller to replicate this.

The immobiliser setting in the Nanocom only turns off the passive part of the immobiliser. This is the bit which includes the 'friendly sync' using the coil around the ignition, but also means that the engine is automatically immobilised if it's been running and the key is removed from the ignition, or after a timeout period. If you don't have a working remote, then it becomes a PITA because normally when you put the key back in the ignition, the BECM pulses the coil, which gets the remote to transmit a mobilisation code to allow starting. If the remote doesn't work, then you need to use the EKA to get it started.
Turning off the passive immobiliser means that it doesn't auto immobilise, and will let you stop engine, take key out, whatever, and then it will automatically send the immobiliser code again when the ignition is turned on - the BECM won't expect a mobilisation code from the fob first.

This doesn't stop the engine from being immobilised when the vehicle is locked/alarmed though, so even with the immobiliser switched 'off' in the BECM - if someone broke it, they couldn't easily hotwire the vehicle and get it started - as the vehicle needs to be unlocked/disarmed before the BECM will transmit the code when the ignition is turned on.

Your alarm problem... It could be an issue with the power/ground feed to the alarm - or it could be the alarm sounder itself that has gone faulty. You could possibly probe the output from the BECM to the alarm sounder to see if it is being triggered by the BECM - also depends if you have the batter backup sounder or if it uses the horn.

I hope that helps...

Marty
 

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Diesel only has 1 code that never changes. Petrol has a rolling code incremented by 1 each time. On the diesel you would have to unsolder the chip in the engine EMS, copy the map to a new chip but not set the security code on the new chip and then solder the new chip in.

The Nanocom switches off the passive immobilisation, not the immobiliser altogether.
 

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Diesel only has 1 code that never changes. Petrol has a rolling code incremented by 1 each time. On the diesel you would have to unsolder the chip in the engine EMS, copy the map to a new chip but not set the security code on the new chip and then solder the new chip in.

The Nanocom switches off the passive immobilisation, not the immobiliser altogether.
I know the Motronic petrol is the same as diesel and has one code.

I didn't know the petrol one incremented though. I know it can have a max value of 65535 though, and heard that LR made most of the later GEMS ones set at that to begin with as it was easier to transmit to the ECU.
 

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Discussion Starter · #10 ·
Thanks to all for your suggestions. I charged the battery overnight and that solved the problem of the alarm sounding with the ignition and then stopping after the engine was running, so thanks OrangeBeam. The voltage at 2000revs = 13.6v. With lights and heater etc running, this drops to 13.3v. So I wonder whether I need to investigate the connections and then the alternator, as suggested in the sticky.

As ever I am encouraged by all the effort and knowledge of the forum members to help numpties like me. I used to run a Series 3, so you can imagine the electronics of my present beloved beast are a bit of a learning curve
 

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The voltage at 2000revs = 13.6v. With lights and heater etc running, this drops to 13.3v. So I wonder whether I need to investigate the connections and then the alternator, as suggested in the sticky.
While you're on a roll it would be a really good idea to work through all of the items in the sticky in detail. With the voltage you're reporting you're only providing a partial charge to the battery which, if it's still any good, will quickly die. In addition, you'll soon be in a world of gearbox fail messages, traction control failures and every other malfunction that is linked to a failing electrical system.
Go for it!
 

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Discussion Starter · #12 ·
Thanks for that. Went for a long long run yesterday. Just now I went to check the voltage with the ignition on and there wasn't even a 'bleep' as I opened the driver's door. Alarm sounded again. The battery is truly on its way out, as you predicted. So a new one will arrive tomorrow, and I shall take your advice and check through the tests and remedy faults before I start getting other fail messages. The alternator I take it is not delivering enough juice, so that will have to be changed. Thanks so much!

Mind you, the price range of new alternators is amazingly wide - from £90 on ebay to £565 for a genuine Land Rover one. I don't want to buy crap - but £565 while what the original owner of my Beast would have been happy to shell out is a bit steep for me!
 

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Don't just scrap the alternator before you've worked through the tests! Put your new battery on (hopefully you went for something like the Alphaline/ Hankook MF31-1000), do the tests, repairing cables and cleaning connectors as you go (you're looking for voltage drops across the cables). Only once you're sure you've no significant (see sticky for numbers) voltage drops anywhere can you get accurate measurements of alternator output at the alternator terminal.
If it's still low, then spend the money on an alternator.
 

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Discussion Starter · #14 ·
Yes I went for the Hankook MF31-1000CCA. Thanks for your suggestion - much more sensible than diving in and changing the alternator. All the best from the other end of the country!
 

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Discussion Starter · #15 ·
Well, here's the update. Fitted new battery, turned key and alarm went off. So back to square one.
 

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Back to the alternator. What's the volatge at 2000rpm with the lights etc on?

If that is a calcium battery it will probably need at least 14.2V. The setpoint on my old diesel is 13.6V so every so often I have to give it a boost from a trickle charger.

The BMW alternator was cheaper than the Land Rover one when I did mine.
 

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Discussion Starter · #17 ·
Before thnewbattery the voltage at 2000revs = 13.6v. With lights and heater etc running this drops to 13.3v. I shall check what it is now - though hopefully not with that alarm deafening me.

Actually it is different this time. After starting the engine the alarm stopped for a couple of seconds then started again. I had to disconnect the battery to stop it.

I shall do the sticky checks. I am also wondering whether there might be a problem with the drivers door because there is still no Beep when I open it. Perhaps turning off immobiliser with Nanocom isn't such a good idea.

Anyway thanks for all suggestions and I shall eat three weetabix before heading outside to confront the Beast.
 

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Before thnewbattery the voltage at 2000revs = 13.6v. With lights and heater etc running this drops to 13.3v. I shall check what it is now - though hopefully not with that alarm deafening me.

Actually it is different this time. After starting the engine the alarm stopped for a couple of seconds then started again. I had to disconnect the battery to stop it.

I shall do the sticky checks. I am also wondering whether there might be a problem with the drivers door because there is still no Beep when I open it. Perhaps turning off immobiliser with Nanocom isn't such a good idea.

Anyway thanks for all suggestions and I shall eat three weetabix before heading outside to confront the Beast.
Don't recall mine ever beeping when I open it. Disabled my passive immobilisation a long time ago!
 

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Discussion Starter · #19 ·
Right, here's another update (for all those still keeping up with the thrilling soap opera...)

Bought repair kit with new batteries for Fob and now the red light comes on when you press a button. As before alarm sounds when you turn the key and I disconnected battery to stop it.

So I reconnected battery with key in position 2, and no alarm. Used Nanocom to change settings to allow key and fob, and enabled immobiliser. Now the alarm doesn't sound but engine is disabled. So I reverted to disabling the immobiliser, alarm did not sound and engine started.

Even with new batteries the fob won't lock or unlock doors. So I think there is a problem with synchronisation. Perhaps the door lock is knackered. If so am I safe to enter the EKA code with Nanocom?

Now that I think I am getting somewhere I have disconnected the alarm under the bonnet.

And I checked voltage at 2000 rpm at 13.4v, the same reading with or without lights/heater.

I conclude that I am getting somewhere but not sure where or how long the journey will be!
 

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13.4V is too low. I would check the voltage drops along the earth straps and the +ve cable from the alternator to the battery +ve.

My petrol P38 shows 14.1V with the engine running, at 2000rpm - which as far as I know is what you should be seeing on a diesel P38 aswell.

Chances are one or the ground straps, or the positive cable have internally corroded and are now causing higher resistance, and thus reducing voltage getting to where you need it.
 
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