Warning - Key Battery problem

[Jeff]

Yesterday I came out of work and key fob opened C5 doors but when I tried to start car it readily turned over but the fuel system was immobilised / orange key symbol on dash.

Luckily a quick sprint across town enabled me to catch a motor spares shop just before they closed. £2.20 secured me their last CR1620 battery and allowed me to return and collect my car.

I incorrectly assumed that as the battery was opening the doors it would start car.

I could have been marooned some where all for £2.20 so purchased another battery today to leave in the car. The spare battery has a best before date of May 2022.

Thought I would post this to warn others. Could be very awkward late at night....

[Hell Razor5543]

That's a sod. Older cars use an inducer circuit to fire up the chip to read it (which is why basic imobiliser keys work without electronics or batteries).

[Jeff]

Just found this bit of advice on the net, not sure what cars it refers to but worth following too:
"some models batteries need to be changed inside 30 seconds to avoid a trip to the dealer for a 'set up' procedure"

[Hell Razor5543]

That sounds about right. Lexia session to re-introduce the keys to the car (and Citroen gets money out of you for a poor design).

[qprdude]

Would be good to know what age of car this was, before everyone panics!

[Old-Guy]

Just found this bit of advice on the net, not sure what cars it refers to but worth following too:
"some models batteries need to be changed inside 30 seconds to avoid a trip to the dealer for a 'set up' procedure"

True! While there's no battery inside, the only thing keeping the fob's memory alive is a tiny little capacitor, so don't accidentally press any buttons either!

[Jeff]

Problem was on a 2001 plate C5

Sorry, I should have mentioned that I noticed battery was losing power as would not open doors from range but the old battery was functioning okay, opening doors from 20-30 metres so presumed (incorrectly) there would be no problem starting the car.

[qprdude]

Phew, cheers.
Hoping that the second key has a decent battery as it's always withing reach.

[DickieG]

Citroen are really behind the times with key remote batteries, with other manufacturers (BMW for instance) the battery is charged by the car whenever it's in the ignition with the engine running.

[qprdude]

But they make up for it by being light years ahead of BMW in most things.
Do any other manufacturers have the key charge thing?

[Mandrake]

So does a C5 key not have a passive transponder like the Series 2 Xantia ? Seems like a backwards step if it relies on the battery to disarm the immobiliser. I really do have to wonder about the thought processes behind some of the silly design decisions in modern cars...technology is getting better by leaps and bounds but common sense in design and application of that technology is going out the window!

[RichardW]

I'm pretty sure it's passive, and this is a coincidence. Discussions around he re-use of 2nd hand C5 keys have revealed that the car writes the code to the key, rather than the other way around, and that this is a one shot operation, thus 2nd hand keys can not be coded to start another car - open it yes, but not start it.

[qprdude]

Remember the OP ,Jeff was having the key problem with an 11 year old car. I don't think BMW had the key charge thing going then, and surely Citroen has moved on? They are usually quite near the front with innovations.

[myglaren]

Remember the OP ,Jeff was having the key problem with an 11 year old car. I don't think BMW had the key charge thing going then, and surely Citroen has moved on? They are usually quite near the front with innovations.

My brother had what would now be a twelve year old 330 that charged the keys while in the ignition - he did have a lot of expensive trouble with the keys though and then sold it due to rust and bought a 307.

[qprdude]

Sons got a 530 diesel. Nothing but trouble . Key doesn't charge either. If it does, one of his keys needed a new battery or something recently so it doesn't work.