C8 key fob not working - help!

[south74]

Hi all...
Today my main remote key fob to my 2004 C8 stopped working... and of course the car is locked with the alarm on.
I have a spare key which I have never used and as sods law is, that doesn't work either.
I have replaced the batteries in both fobs... and neither work.

My question is - how can I disable the alarm and start the car if I don't have a working key fob?

If the fobs need re-coding for some reason, Citroen say it's £54. but I can't get the car to them!

Is there a work-around to disable the alarm and immobiliser without a working fob? I was told that I should unlock the car directly with the key, open the door, insert the key into the ignition and turn on whilst pressing the interior volumetric sensor button inside the door hinge/end of dashboard. Hold for a few seconds and then the alarm should deactivate.

This didn't work.

Any other ideas?

Thanks in advance

[Paul-R]

The remote control part of your key fob is a separate circuit to that which starts the car. If you unlock the car using the key in the door lock and open the door that way (as per your previous advice) the alarm will start. You need to quickly put the key into the ignition and start the car up - this will then stop the alarm as well.

Then you can sort out the remote locking at your leisure.

[GiveMeABreak]

If the batteries in the fob have been replaced it may need reinitialising.

First, to disable the alarm, open door with the key, put the key in the ignition and turn ignition on - that should be enough to stop the alarm. Remove the key.
To reinitialise the key, place the key with the fob buttons facing you into the ignition, turn ignition on and within 10 seconds, hold the LOCK button down continuously for at least 5 seconds.
Remove key, close vehicle and then operate the remote which should now operate the central locking. Ditto for the second fob if you have a second fob.

If you lock the car with the key, then deadlocking is not activated. But if you lock with the fob, you should unlock with the fob.

As Paul says, the transponder circuit works based on a chip in the key being in proximity to the ignition aerial ring and this will allow you to start the car. The remote locking is separate.

[south74]

Thanks guys.

I managed to get the car running by disconnecting the battery for a few mins... reconnecting... waiting and then trying the sequence again. Then the engine started and the alarm stopped.

As for re-initialising the key fobs... are you sure that is the process for a mk1 C8? It doesn't seem to work. I have tried it several times. Any other thoughts? I'd love to avoid having to go to a main dealer because I'm sure that they'll say I need to buy new keys or something like that!

[GiveMeABreak]

Page 17 of the manual lists a simplified procedure insert key, switch on ignition and immediately hold LOCK button down for up to 10 seconds until action is completed.

Other issues to consider:

• Have you replaced with the right battery coin cell - these take a CR 1620 3V
• Have you dropped the fob and inadvertently damaged the PCB. A colleague did this and the microswitch under the lock button was not engaging. I had to solder it back on, then all worked.

[south74]

The batteries in both fobs are correct and brand new today.
There doesn't look like there's any damage to the PCBs - visually anyway...

...but the re-initialisation procedure you mention doesn't make any difference... neither fob work.

[GiveMeABreak]

What is happening exactly? Is the alarm going off all the time? Have you tried a BSI reset?

[south74]

Up until yesterday, everything was working fine. Remote central locking/unlocking, alarm set/un-set.
The spare key fob has never been used, ever, and has never worked since I bought the car (secondhand) 7 years ago.
Yesterday, I went to unlock the car with the remote key fob and pushing the button did nothing - like the remote/fob battery was dead.
I could open the car with the key, obviously... but then the alarm would go off and the car wouldn't start because of the immobiliser.
By disconnecting and reconnecting the battery (I'm guessing that this resets the BSI) I managed to run the sequence of unlock door, open, key in ignition, turn and press the volumetric sensor button to disable the alarm and immobiliser so that I could start the car. (It took a few goes, but eventually it worked)
Now, having replaced both key fob batteries (with the correct ones) and aslo having performed the re-initialising sequence - neither of the fob remotes work. i wasn't expecting the spare fob to work, but I was expecting my usual fob to start working again.
So... I short... the car works... it's the remote key fobs that don't.... which means I don't have the remote open/lock/sliding door functionality at the moment.
If the fobs need to be re-coded, I wonder why the system has lost the configuration.
Incidentally - I check for errors on the global test diagnostic Lexia and it's all good (apart from the usual errors!). I can't see any function in the lexia which is to do with keys... or key pairing...

[Paul-R]

I could open the car with the key, obviously... but then the alarm would go off and the car wouldn't start because of the immobiliser...

The alarm going off is correct but putting the key into the ignition and turning it silences the alarm. This shows that the car has recognised a correctly paired key (the alarm wouldn't go off otherwise) and you should then be to actually start the car. If the car doesn't start after silencing the alarm then something else is wrong.

The vehicle really needs a session with a Lexia/Diagbox.

Incidentally, the second key may never have worked the remote locking but does/has it ever started the car?

[south74]

the second key may never have worked the remote locking but does/has it ever started the car?

Yes - no problem starting the car with either key.

putting the key into the ignition and turning it silences the alarm.

It didn't silence the alarm until I had disconnected and reconnected the main battery... effectively doing a BSI reset.

The vehicle really needs a session with a Lexia/Diagbox.

I have checked for errors with my Lexia and there's nothing obvious when I do the global diagnosis. Maybe there's an error somewhere deeper in the Lexia app that I haven't found yet.

[Paul-R]

Maybe the sensor coil that wraps around the key barrel is faulty. This coil recognises the identification chip in the key. I have read about one being faulty some time ago - possibly here so I'll have a dig around.

[Paul-R]

Had a search and couldn't find anything - sorry.

[south74]

Ok - thanks anyway.

[GiveMeABreak]

That Transponder Aerial doesn't need to be coded either - it just picks up and sends the data, so any second hand replacement will go straight on if it is that.

Back to the alarm - so you can do without it temporarily just by locking and unlocking with the key. The only other thing I can find is that it will activate if there is a cut in the electrical supply - restoring the electrical supply and turning the ignition is supposed to disable the alarm.

As you have mentioned connecting and disconnecting the battery, I would follow a FULL BSI reset procedure including giving the car plenty of time for the multiplexed networks to go to sleep, before opening any doors and disconnecting the battery - then leave the battery off for a good 10 minutes to ensure the ECUs are fully powered down, before proceeding with reconnect (and be aware that if you touch the battery terminal when reconnecting and it breaks contact before you get is secured - you have effectively switched the ECUs on and off and on again, which defeats the object). So nothing to loose by trying an extended disconnect and reconnect within the procedure.

[GiveMeABreak]

And one other thing I completely forgot to mention - how old is the main car battery? These C8s have a lot of electrical equipment and they, like the C5 need a good healthy battery, or the electronics start playing up. The fact that it may start up quick enough is not always an indication of the overall health and charge of the battery. Just another thought!