Hi, just had a call from my wife who needed talking through the EKA unlock procedure. I sense strife when she gets home!

There is only one fob with the car, and it seems flakey. Sometimes the key fob seems to be transmitting fine (flashy red light etc) but the car won't unlock. You can hold it next to the rear windows, point it at the antenna, dance on one leg - nothing.
So you open the door using the key and the BECM demands the EKA before allowing the engine to start.

What's going on? I've had it happen to me when I'm sure I haven't pressed any fob buttons at all between lock and unlock, but I will admit it never seems to happen immediately after locking.

Have you thought about it from the other angle Morat? That it's not the fob having a hissy fit, but external RF interference throwing the BECM into a paroxysm of self doubt?
Do you have the Gen III green spot receiver on yours? If so, then it probably is the fob. Maybe a bad battery contact?

I would suspect that in the wilds of Yorkshire there's probably not a lot of RF about to cause the receiver to throw a wobbly, more likely a dodgy battery connection in the fob. One of the solder connections on the big ring contact does have a habit of cracking, so that might be the problem.

Both good suggestions but...
Could be RF I suppose, but it's very unpredictable even in similar locations. I guess I need to check the RF receiver... erm.. I'll go look it up :)

The battery contact is something I check, but if there's a red flashing LED when I press the tit.. it's got to be working hasn't it? Or does it lose its mind if there's a temporary loss of contact while the thing is sitting in your pocket? Hmm, that could make sense if the rolling code is stored in volatile memory.

Yes, the rolling code is stored which is why the handbook tells you not to take more than a minute to change the fob battery or it will lose sync. However, on a later car like yours, it should re-sync as soon as the key is put in the ignition although I'm not sure if that still applies if the car has been unlocked with the key rather than the fob.

Ahhh, that's making sense. Thanks Richard. I'll have to have at the fob cover and batteries to make sure they stay in firmly. I got so pissed off with it all last time round that the back cover is gouged and doesn't have the rubber seal because I just couldn't make it turn. It's likely that the code is being lost and that's leaving the key/door lock as the only way to get in.
After you enter the EKA, the key syncs up just fine.
Replacement fobs are just so damn pricey.... :(

I had one of the fobs for the new one fault checked, repaired and re-cased for the pretty reasonable sum of £50.00
http://www.fobfix.com/products/range-rover-p38-button-remote-key-fob-repair-fix-service?variant=8538459909
V happy with the end result. Course, as you just have the one fob you'll be P38less for a few days.

You can stick in a 2035 battery to pair with the 2025. It's thicker and will take up any slack.

Just a thought Morat, but you could just not use the fob to lock the car and use the old fashioned key in the door technique. Use the fob occasionally under controlled circumstances to make sure it's still synced and microswitches OK, and you have it as a back-up.
I've been doing this on my GEMS since I bought it (cos its got the original receiver and where i live is saturated with 433 RF) and haven't had any issues with lockouts.
Bet I've cursed it now and will go out later and find it's locked out, but I do have the EKA and Nano to fall back on!

To me this whole fob issue is still a mystery. I have 3 fobs, #2 and #3, the third one is unreadable with defective microswitches and will probably be #1.
If I change fobs I first have to lock/unlock with the blade and from then on the fob works without synchronising or any messages. (Touch wood of course)

that is pretty mysterious!
I'm going to change the batteries and cover/seal on the fob again and hope to maintain a constant contact. I've got some holiday coming up so I'll dig into the parcel shelf then and see what version of RF receiver she's got. I'm guessing it's the original or the PO would have told me about it.
There's a surprising amount of RF where we tend to park, I'm the local repeater for our Wireless ISP which isn't on 433MHz but I hear the earlier units don't discriminate too well.
At work, there's phone tower on the roof and loads of WiFi, plus various wireless alarm systems etc.
It sounds like there's more "investment" to be made!

Earlier units don't discriminate at all - they'll let everything through to wake the BECM up...

The MK II unit, which you SHOULD have, being as the Duchess is a 2001, has better band filtering to stop interference from waking the BECM up and then draining the battery - but there's still a lot on the 433mhz spectrum which can cause problems.

The MK III Receiver has some extra chip in it which identifies the transmission as a P38 fob code, and will ONLY wake the BECM up if it's a P38 code - which is what fixes the battery drain, as the BECM isn't constantly being awoken from slumber to check every transmission.

The thing is that none of that will stop interference from messing with the fob signal from the fob to the receiver. I get it on mine sometimes where I'll go to press unlock, and nothing happens.. occasionally if I press the lock button it will then communicate, and I can press unlock again straight after and it's fine.

I guess if there is still a lot of RF it could in theory mess with the data packet being transmitted to the vehicle, and that means the receiver/BECM doesn't recognise the transmission properly and thus sits there blissfully ignorant.

I could also be completely wrong :) but it definitely can't hurt to do the batteries again - I wrap a bit of tape around the edge of them as the bottom one can short to the metal tab and then you only get 3V not 6V to the fob PCB - which is enough to make the LED flash, but give issues with the transmission aswell.

Do it with the vehicle unlocked, and then you won't have any issues with the alarm/locking when you go to resync it...

Very interesting Marty. I've noticed the reverse behaviour to you - sometimes it will only lock after I press unlock. I thought that might be some way of preventing you from locking the keys in the car but thinking about it.. that makes no sense :)

I'll definitely take the tip on the tape round the bottom battery. Thank you.

I need gilbert to come buy with his work van to sniff the airwaves :)

You've got nothing more than would be found anywhere else. The wireless ISP equipment will be on 2.4 and 5.8 GHz, usually 2.4 for the access points and 5.8 for the backhaul. Phone tower will be upwards of 926 and, depending on the operator, 1.8, 1.9 and 2.1 GHz so nowhere near 433. The only other thing is wireless alarms which, if they are older ones will be on 433 but newer ones are on 868, but even then, they will only transmit when the alarm needs to be triggered (although I have come across older 433 window sensors that transmit constantly when a spider takes up residence inside them). About the only thing you have even remotely close is your own Hytera base station on 453.

I've no idea what receiver is in mine, I've never had cause to look but I've only ever had a problem three times in the time I've owned it. Once in a country pub car park, once in the centre of town (both down to something being on that shouldn't be undoubtedly) and once at home when the battery started to die in my heating oil level sensor and it went onto permanent transmit.

My money would be on an intermittent problem with the fob. If you can get a key blade cut to use in the interim, I'd be inclined to send it for a full refurb to the place OB suggested.

I have got the new Mk III receiver, two working fobs and I still occasionally get "engine immobilised" then "press key fob".
This occurs when using either key. Receiver was brand new last year after suffering battery drain parked outside my house.
BECM was also cloned last year and a newer one fitted. What gives? 2000 MY diesel.

I'd think that high-powered "wideband" RF noise can still overwhelm the receiver. Maybe it's smart enough to think it's being attacked and lock itself down? Doubt it though.
Does it always immobilise in the same place, or is it random?

It seems to be random. However, having said that, it seems to occur more when I unhook the caravan and use the caravan's built-in motor mover (433 MHz). I come to restart the car and it says immobilised. I usually leave the engine running now when positioning the caravan. It does occur at other times but it usually restarts right away after pressing the fob.

Thinking the new receiver meant the end of all my problems, I programmed the replacement BECM with everything turned on. Maybe I should switch off some of the security features? I know the BECM starts to loose its memory with age (like the rest of us) so maybe it is loosing sync with engine ECU possibly?

Orangebean wrote:

I'd think that high-powered "wideband" RF noise can still overwhelm the receiver. Maybe it's smart enough to think it's being attacked and lock itself down? Doubt it though.

I put a 'scope on the back of my own (Ist Gen) Rcvr. once and was amazed at how much RF stuff it picked up, from frequent random bursts to very infrequent and slow pulses: It was basically acting as though it was a wideband Rcvr ! Some of this impinging RF (if powerful enough) will probably swamp the front end of the Rcvr. too. But the main problem I suspect is the BECM seems to behave as though it counts RF pulses etc (from any/all sources) and then may 'get difficult' beyond a certain number of what it perceives as multiple attempts to communicate.... Didn't establish exactly how many bogus pulses it took to upset the BECM like this but it may have been a lot (20+ ?) which can happen in some places in a few hours of course. (Note for this 'test' I basically stood next by the car continually operating a non-LR but 433Mhz 'plipper' -for some time- until the " Key Code" lockout showed up - and it didn't always do this either... aka 'a non-conclusive experiment' !)

I may be wrong, but I don't think "Engine Immobilised" is the same as BECM/ engine ECU lost sync. Mind you the diesels do their security stuff slightly differently.

Ok.... my observations on the 3rd gen receiver so far...

As far as I know it must look at the header in the transmission and identify that as being a valid P38 transmission. If it detects one, then it passes it onto the BECM for decoding to make sure it is the one for your vehicle.

Just because the 3rd gen receiver stops the BECM from waking up every time there is a transmission of any kind (1st gen receiver) or a transmission on 433mhz (2nd gen with extra filtering from what I gather) it doesn't mean it's immune to interference. The only difference is, that it's now blocked at the receiver end - so if it isn't a P38 fob transmission, it won't get passed onto the BECM/cause excessive battery drain etc.

Engine Immobilised - Press Remote is not engine ECU sync. If you have lost sync then on a diesel, it will crank but not fire up and run, but you won't get any message on the dash.
Engine Immobilised is from the BECM end - as in it has immobilised the engine again. If you have the 'immobiliser' feature turned on in your BECM, then this is completely normal. The passive immobiliser will automatically immobilise the engine after it's been switched off for a period of time. The normal practice is that when you put your key back in the ignition, the key in switch tells the BECM the key is there, and it will then pulse the coil around the ignition to then get the fob to automatically send an unlock code, which the BECM will receive, and then it will allow you to start the vehicle again (it should be seamless).

If it comes up with the message on the dash, then it basically means that the BECM hasn't received a valid code from the fob automatically, which could be down to a number of things - the coil around the ignition not working or intermittent, the key in switch faulty or intermittent (so it doesn't know you've put the key back in the ignition) or maybe the 3rd gen receiver has a 'time out' function on it - where if it's inundated with interference it then goes into a time out where it waits for x long until it listens for transmissions again. Or, maybe if you've been using the caravan mover on 433, it's swamped the receiver, and it hasn't cleared the data out of whatever buffering it has, in time for it to receive the fob code from the BECM.

The easiest way to sort it... turn the passive immobiliser off in the BECM settings. This will then mean that it won't time out and immobilise the engine automatically, and it also disables the coil around the ignition (so no 'friendly sync - you'd have to do it in the door every time). The vehicle will still be immobilised when locked/alarmed - whether by the remote or the key - but when it's unlocked/disarmed it will always allow you to start it straight away.

As to why it isn't either getting the fob to automatically send a code again, or it's not receiving it - I don't know, but what it's doing by immobilising the vehicle automatically is perfectly normal with the passive immobiliser switched on.

So have we got an idea what sort of header the key receiver is looking for? Sounds like the sort of thing an "aftermarket" box could be created for.