Td5 disco 2 wouldn't start

Rangie Disco Sportsman said:

Disconnecting and reconnecting the too battery quickly I seem to think does cause the alarm to go off and fob to stop working and solution is hard battery reset (remove terminal wires and touch together to discharge capacitors in electronics and wipe their memory

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No such thing for D2 and i doubt that any ECU will end up with wiped memory after that "hard reset" thing, the hard reset is effective for CAN-bus vehicles(D2 is not) to discharge capacitance of the data bus cable, nothing to do with ECUs whatsoever cos all the EEPROMs are ''isolated'' from the battery through the ignition switch and through transistor switches on the PCB ... i've seen that hard reset theory on many forums and IMO it's a false myth that it has any effect on a D2, it's completely useless

Hi @sierrafery , Mr uselesswitheletrickery here again. what if you disconnected the battery and then jumped in the truck and switched the ignition to drive, i.e. one short of start? And then maybe turned all switches on, moved the gear select lever all over the place, put your foot on the brake hard and ditto the accelerator. What would that do?
I am expecting to hear "Nothing"!!!

Stanleysteamer said:

I am expecting to hear "Nothing"!!

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If that's what you expect you'll not be surprised nor dissapointed

sierrafery said:

No such thing for D2 and i doubt that any ECU will end up with wiped memory after that "hard reset" thing, the hard reset is effective for CAN-bus vehicles(D2 is not) to discharge capacitance of the data bus cable, nothing to do with ECUs whatsoever cos all the EEPROMs are ''isolated'' from the battery through the ignition switch and through transistor switches on the PCB ... i've seen that hard reset theory on many forums and IMO it's a false myth that it has any effect on a D2, it's completely useless

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You'll see it because it definitely works and I use it reliably every time the vehicle is left and the battery goes flat. Jump it and the alarm goes off and fob won't work. Disconnect battery, touch terminals together, reconnect and it's all fine.

Next time simply disconnect the battery, charge it, reconnect it and unlock with the fob without joining the battery leads and you'll see that it has the same effect... though i insist that what ever you do with the battery leads will not wipe any memory as you said in your first reply

sierrafery said:

Next time simply disconnect the battery, charge it, reconnect it and unlock with the fob without joining the battery leads and you'll see that it has the same effect... though i insist that what ever you do with the battery leads will not wipe any memory as you said in your first reply

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The alarm will go off when you reconnect it. If what you describe worked I wouldn't need to bother disconnecting the battery again. The same happens if I put a fresh battery in, The issue seems to occur with the alarm when the battery has gone completely flat in the vehicle. If you don't touch the wires I'm pretty sure you have to wait longer after disconnecting the battery before reconnecting again.

It was just added as a general description of a hard battery reset for a casual reader - You insisted to me before that there's absolutely no way technically that the air suspension compressor will operate after the igniton is turned off and the vehicle locked and that wasn't/isn't correct in reality.

Rangie Disco Sportsman said:

You insisted to me before that there's absolutely no way technically that the air suspension compressor will operate after the igniton is turned off and the vehicle locked and that wasn't/isn't correct in reality.

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I dont think i said there is no way for the compressor to work with ignition off, i'm sure i insisted that it's not supposed to/not normal behaviour ... though no need to go off topic or argue on this, you can continue to believe that hard reset wipes memories on a D2 no probs

sierrafery said:

I dont think i said there is no way for the compressor to work with ignition off, i'm sure i insisted that it's not supposed to as it's not normal behaviour ... though no need to go off topic or argue on this, you can continue to believe that hard reset wipes memories on a D2 no probs

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Well the issue is coming from the vehicle being locked and the battery going dead so is opened with key rather than remote and the bonnet is open then powered back up. When you put another battery in the car basically remembers it was last left locked and hasn't been unlocked properly so off the alarm goes. I know the other solution is to manually lock the doors, after you've popped the bonnet and activate the bonnet switch before connecting the new battery so everything then appears to seem fine when the car powers back up. As disconnecting the battery again and leaving it a while or touching the terminals together definitely does work also, it suggests to me that it is somehow wiping the car's memory of being left in a locked state. I'm not imagining this it is my regular routine every time I go back to my Disco 2 after leaving it parked for a couple of months because it's less hassle than putting something on the bonnet switch whilst I put a charged battery in. I don't really have to believe when it is a procedure that is working somehow as I'm sure anyone else who has the same problem probably isn't bothered if the technical description of why it works is right on every point of pedantry.

Rangie Disco Sportsman said:

As disconnecting the battery again and leaving it a while or touching the terminals together definitely does work also, it suggests to me that it is somehow wiping the car's memory of being left in a locked state. I'm not imagining this it is my regular routine every time I go back to my Disco 2 after leaving it parked for a couple of months because it's less hassle than putting something on the bonnet switch whilst I put a charged battery in.

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Maybe there is some residual capacitance in the wiring but the simple and correct thing is to unlock with the fob after you reconnected the battery and that's it, no need to undo terminals again or "hard reset"

sierrafery said:

Maybe there is some residual capacitance in the wiring but the simple and correct thing is to unlock with the fob after you reconnected the battery and that's it, no need to undo terminals again or "hard reset"

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Really, all this time and I never thought of that - (of course I have) the fob won't work although it works normally and works again fine without any resyncing type faff when the battery is reconnected for the second time.

Ok then we can agree that you have a strange D2 ...cos mine disarms the alarm with the fob every time i reconnect the battery if it was flat, or if i simply jump it(exactly as it should) and the compressor never works with ignition off(exactly as it should)... i can tell only what a D2 which is working as it was conceived to work must do, i can't explain all oddities but i'm sure that there are more correctly working ones out there then strange ones....i'm not contesting what you experienced but i'm 100% convinced that the "hard reset" is a procedure for CAN-BUS vehicles(like D3-4, RRS, etc) and it's also mentioned in theyr's manuals while i've never seen that procedure mentioned in a D2's workshop manual or other official document nor has any technical/logical explanation as it can't have anything to do withthe D2s EEPROMs

Well latest is I am stranded on a main road and every time I try to put the key in the alarm goes off!!

The alarm only deactivates when I turn the key in the lock physically but when I try to start it it goes off again

The fob buttons light up but dont do anything to stop the alarm, so I am guessing it is the after market locking installed that is causing problems somewhere

Either way I am stuffed on this main road and its increasingly embarrassing trying each time only for the bloody alarm to blare

Well the very patient and very kind local mechanic helped me out. Car just started again on it's own

He checked the battery which tested as "good" BUT

The negative terminal on the battery moved when he was unscrewing the cable and the positive terminal has actual gouges out of it, proper gaps in the metal..!!!

He cleaned it up and the car started but could the fact the positive terminal literally somehow has cuts out of it be causing the immobiliser issues?

The standard method and hardware for mounting connectors to the battery terminals is SH1TE!
I have found it a good idea to clout the terminals down on the posts with a socket of the right size before even trying to tighten them without allowing them to rotate on the posts. Alternatively, try going back to old fashioned terminals which work very well. LR's motto "If it ain't bust, fix it"

Could this rust in the battery compartment of the fob be causing my problem of the immobiliser only once every few times immobilising and only sometimes deimmobilise when I press the unlock button on the fob?

The led lights up every time but doesnt always switch the alarm off?

If the corrosion got to the PCB too it can affect some circuit without stopping the LED to come on so better check further

Sierra my old friend...

I have worked something out... if I hold the original fob right beside the receiver at the rear sunroof, it stops the alarm and immobiliser.if I stand well back, it doesnt... so... does that suggest a problem with the receiver if it only works with the key right beside it?

I take it once it has registered once and then starts the car it doesnt "talk to it" whilst I'm driving so that's why the immobiliser doesn't sometimes come on when driving?
Bizarrely, the original fob locks the doors still, but wont unlock them, I need to use the aftermarket one to unlock them

Is it possible this was the reason the old owner installed an aftermarket one, the problem with the receiver and if I fix that I can get someone to remove the aftermarket one hopefully and go back to original?

That rust really can't be helping can it!!!???
Also there are threads on here about the thing in the roof and how it misbehaves when it gets wet, which can happen when water leaks in through the sunroof frame.
If I were you Id search for it on this site, you will find something on it. Try this https://www.landyzone.co.uk/land-rover/central-locking-receiver.319378/#post-4057922

Millertime_9 said:

I take it once it has registered once and then starts the car it doesnt "talk to it" whilst I'm driving so that's why the immobiliser doesn't sometimes come on when driving?

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That's impossible as long as there's nothing wrong with the BCU...the immobiliser is supposed to kick in only with ignition off, and yes, you should replace the RF receiver to be ruled out

sierrafery said:

That's impossible as long as there's nothing wrong with the BCU...the immobiliser is supposed to kick in only with ignition off, and yes, you should replace the RF receiver to be ruled out

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Ok so bearing in mind the fob works when its right up against the receiver (headlining is out) then its a signal issue either with the receiver or the fob?