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C4 - DS4 Owners :: Forums :: Citroen C4 Picasso and Grand C4 Picasso (B78) 2013 onward :: C4 Picasso and Grand C4 Picasso (B78) Problems and Issues

Key Fob Not Recognised : Problem & solution

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Thu Jan 10 2019, 11:19am
Member No: #42824
Joined: Nov 29 2015
Location: Cardiff
Went out to the car, touched the door handle - nothing

Pressed the unlock button - nothing

Pressed the boot open button - nothing

Used the key, it's a turn & hold, and click, mirrors out doors unlocked.

Open door and the alarm sounds, press start button - Key Fob not recognised.

Alarm will not go off.

Put fob in holder, - alarm will not go off.

Take fob from holder and hold it for a few seconds, and all of a sudden it all works and the alarm is off.

What I had done that was different was, that last night I left work and found the boot open and decided that I must have operated the boot open button whilst in my pocket.

Today, to prevent accidental operation, I clipped the key to my bag. which is on the floor, where the temperature is about 2°.

A few hours after not being able to get in the car, I gave it another try and nope, I couldn't get in again.

I held the fob in front of a fan heater for about 10 seconds and all works again.

The fob stops working when it's cold!!!

Keep it in your trouser pocket and it will stay warm and work.

Keep it in a nice warm house or car and it will work,

But let it get cold and with this one at least, it ceases to function.

I'll give the other fob a try tomorrow.

At least you all know of the solution now, but maybe give yours a try after putting the fobs in a fridge for a while to see if it's a common problem.

Whatever, If it is a problem. I can't see Citroen doing anything about it.

Maybe it's just a cold battery thing.

Thu Jan 10 2019, 12:11pm
Member No: #27768
Joined: Oct 13 2012
Location: Hove
Probably a knackered battery, the terminal voltage drops when they get cold. It probably dropped just enough to become problematic.
Thu Jan 10 2019, 01:30pm

Member No: #82
Joined: Jan 22 2007
Location: Hoylake
Yes, time for new battery.
Thu Jan 10 2019, 04:14pm
Member No: #46470
Joined: Oct 11 2016
Location: Cambridge
The voltage/current/service life fall off with some button cells at low temperatures is marked. On top of that, silver oxide types have a cliff edge fail point, nice slow decline from 1.5v to a bit under 1.0v then nothing.

So - new battery. Might as well do both, likely they will both be the same age.
Thu Jan 10 2019, 05:19pm
Member No: #42824
Joined: Nov 29 2015
Location: Cardiff
Thanks people, I'd sort of came to that conclusion when it worked when warmed up. I'd posted more as a heads up for others who may suffer the same fate and get stuck out in the cold.

Will use the other fob until I get some new button cells.
Fri Jan 11 2019, 08:26am
Member No: #42824
Joined: Nov 29 2015
Location: Cardiff
I put the other fob under the same cold conditions and got the same result, so next I'll change both sets of button cells and will give it a try then.
Mon Jan 14 2019, 01:04pm
Member No: #42824
Joined: Nov 29 2015
Location: Cardiff
Well, I changed the fob cells (CR 2032 lithium), got them cold and they both still worked. So, I now know they last just over 3 years.

Not too bad on cost: 4 x CR2032 + 4 x CR2025 89p.

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