On my 2006 E61 I have an intermittent key fob issue. The other day (in the pouring rain) it wouldn't unlock on the fob. Used the key, set off the alarm, put the fob in the slot and the noise stopped. I clicked the lock/unlock buttons a few times and it all worked fine. Got home, locked the car using the fob and left it. Next day I went out and it wouldn't unlock again. There are no battery warnings for the fob when it's inserted in its slot. What's most likely? Fob battery? Diversity antenna? Tailgate wiring damage? I can check them all but wondered where to start. The battery in the spare fob is totally flat so can't try that for now! One potentially related thing - left rear fog light bulb fault keeps popping up on the dash. The bulb tests fine, so perhaps this is pointing to a.loom problem on the left hinge?
Battery I would say. From memory when I had my E60 M5 I was told the key battery recharges or something like that when inserted in the ignition slot? If it does then it seems that the battery is failing and discharging overnight?
I did wonder. I will try changing it. I'll look it up bit if anyone has a decent guide to battery change be appreciated if they could post up a link .
Sounds like fun. I’ve read contradictory advice depending upon whether the car has comfort access or not. Some say simply change the battery, some say you can’t change the rechargeable ones. There are a few posts saying put the key on a toothbrush charger as that uses the same process as the slot in the dash….random. Hope you get it sorted.
I think I got to the bottom of it last night. It seems that comfort access (I never understood what that was but appears to be keyless start - i.e. you keep the key in your pocket and the car knows its there) has a battery you can change easily. I think the rationale is that it never goes in the dash so wouldnt charge even if it was rechargeable. The non-comfort access has a pretty much sealed key fob with a rechargeable battery in it that charges while its inserted in the column slot. But i guess even these rechargeables have a limited lifespan and mine will be 18 years old now. It seems that you have to snap the glue apart on these fobs to change the battery, then desolder the old one and then solder a new one in. I should be able to do that as long as i dont wreck the fob plastic in the process. I will try on the fob thats currently totally dead first and simply wont charge at all so really does need a new battery (although i will also try the toothbrush charger trick!).
Maybe look to buy a new fob on the “just incase” approach. Think they are relatively cheap to buy now. https://ebay.us/m/ozial2
Quite impressive that one of the batteries is still working, even if it is on its last legs. The battery performs just one function: remote locking and unlocking. The chip inside does the rest. You can withdraw the key from the fob to manually unlock and lock the car. Inserting the fob enables the security functions, eg cancelling the alarm, start/stop, et cetera. If you manage to replace the batteries in both fobs, get into the habit of alternating their use to keep both batteries charged. Once a battery is completely flat it’s quite difficult to revive it.
So I'm fairly sure this is a wiring issue now. Until I get time to take the tailgate wiring apart, is there a way to lock and unlock on the key without setting the alarm off on unlock?
I'm fairly sure that if you lock the car with the key the alarm won't be set, and therefore won't go off when you unlock. The tailgate wiring fix is fiddly but not that bad. You'll find a few broken wires. You can charge your key (just to make sure it's not the key battery) by leaving it on an electric toothbrush holder overnight. Just rest it on/as close as possible to the middle. I do this regularly to 4 keys that I have and it definitely charges them.
Thanks for that. I charged the good key as you advise and it did nothing. It works randomly along with intermittent messages about the rear left fog light. So I reckon it's broken wires in the rear left hinge. I have a repair kit I used on my old e39 touring so have the bits I need luckily. Just no time at the moment. Chopping wood for winter is taking priority currently (I'm 9 tons in!)!! I'll try the lock on the key and see what it does.
Just for info. Locking on the key does arm the alarm so it goes off on opening the door after you've unlocked. The minute you put the fob in the column slot it stops . It doesn't seem.like there's a way to disable the alarm with the key (I.e. turn again within 30 secs doesn't do the same as pressing the lock button again for example) BUT... if you unlock on the key, and hold the key in unlock, it lowers the windows. This doesnt teigger the alarm and means you can reach in and put the fob in the column slot which will disable it without it sounding! It's a bit clunky but will do until I can fix it all!
Sooo..... just returning to this. I haven't changed the key fob battery yet. MOT is coming up and rear fog light isnt working on the LHS so I thought I would take a look at the tailgate wiring. Broken wires everywhere. I did the left side. Fog light wires broken, ground to rear heated screen totally snapped to the point that it must have got hot and also melted the rear washer tube. I thought, right side is working but i will check it all anyway. I think I had to replace all but about three out of around 12 wires. Interestingly the 12v live to the diversity antenna was totally broken. I had totally forgotten but it looked like I had been in there before (I didnt do the tidiest job then but this is a lot better now). So, after two evenings cramped in the back of the car, they are all repaired and spliced back together. Replaced everything, tried the key fob....AND.... nothing I have checked the earth at the diversity, that has continuity to earth on pin 5 (brown wire). Pin 1 - 12v, pin 2 4.7v (I think 0.7 but may have been 0.2), pin 3 has 12v when ignition and radio are on which i think is normal, ign off and it reads 0v. So, wiring and power to the antenna is good. The coax on the left side all looked good, so all connections to the antenna seem to be what they should be. Fuses - i checked everything in the glove box that was listed against the door with a key in the window. They are all good. I checked 77, 79 and 69 (I think) in the boot. Are there other fuses related to this unit? Diversity antenna board looks spotless - I know you cant tell by looking but there is no corrosion that i can see at all. I think i may have sprayed it with a laquer years ago (a friend of mine recommended this with my E39 after he repaired it for me so I think I may have done it with this one too a long time ago! So.... I am stumped. - Key fob battery? - have a new battery but it does mean breaking the fob apart and the dash isnt telling me the battery is flat (it does for the spare battery). - are there other fuses to check that arent obviously marked for the central locking? - could still be the antenna but i am doubtful and why would it have been working until very recently then finding all those broken wires i assumed they were the reason it suddenly stopped. It had really great range before it suddenly stopped working in September - like 75ft range - Do I need to start the car since its been stood for a while and battery disconnected whilst I did these repairs? - Anyone know the process to re pair a non-comfort access key? All the online instructions say to put the key in and turn to position 1 five times.... well, I fail there as you dont turn this key, just insert it in the dash and press the stop start button. - What else?
I checked all fuses earlier. They are all fine. I started the car too and still nothing worked. Reading around, it sounds like pairing occurs when you put the key in the socket on this car - not sure if thats true. I will try and change the battery in the fob i know is definitely not charging (as nothing to lose there). Re-inspection of the diversity board shows a tiny bit of crusting on the underside in the side where the coax cable connects, but nothing really bad. Starting to wonder if it is this. I have contacted a local electronics place to see if they can take a look at it as that may be cheaper than a replacement. I am reluctant to go second hand as no guarantee is will be any better and new is just crazy prices!
Weirdly, with the harness plugged in to the diversity antenna, pin 2 reads 1.84V. If its not plugged in, it reads 4.7 as above
That doesn't sound right but it depends what pin 2 is, if it's a data line then the your meter may just be reading an average of the voltage. I'd focus on a finding out how to resync the keys now. In theory the wiring is correct and the fob batteries have some charge in them.
Thanks. I've searched high and low for the key sync process. The only instructions I van find involve inserting the key and turning to position 1. You don't turn my key, you put it on and press the start stop button, then the searches fail. Someone said it syncs every time you put it in the slot to start the car but I don't know if that's true.
