C5 immobiliser / aftermarket key

[jgra1]

morning all

chaps, yesterday the C5 wouldn't start, immobiliser fault.. for the third time since I got the car..
the usual banging about on the engine-side fuse box made some clicks but wouldn't cure the problem this time..

I got the lexia on last night, and the ECU was locked, the key was no longer paired...
spare key unlocked ECU, cleared faults etc and this morning the car started on that key..
shortly after I tried the main key but no go, again...

the odd thing is, the main key, a triangle quite chunky one, has no buttons at all, but does have a battery...
is this a case of the transponder chip being an eprom powered by the battery, and eventually running out? if so, it's the first time I have come across it on a PSA car..?
I could be barking up the wrong tree - but what does the battery do?

I will try another battery anyway, and see if I can work out how to re-pair the main key again, although not done anything like that with a lexia..

thanks for any suggestions on this..

John

[Hell Razor5543]

IF it is the key, you will need the security code to access that part of the Lexia/car menu, and you will need to do all the keys (any that aren't done will then be 'ignored').

[jgra1]

thanks James..

do have the card code thing somewhere..

[RichardW]

As you indicate in title John, sounds like an aftermarket key - all the Citroen ones have remote locking buttons on them. Could be a generic jobby that has an e-prom rather than a solid state chip as per original. You've not got much to loose by changing the battery after all - you might need to re-code it to the car afterwards, as it appears to have already forgotten the code.

[jgra1]

thanks rich.. think an aftermarket alarm was fitted.. which i am not sure even works...

just a bit worried about the whole recoding thing.. would hate to disable car completely... will try a batt anyway first..

[jgra1]

on the circuit board.. there is a wound core (shown as a white cylinder in pic).. that has lost contact.. could well be the problem, but my soldering is useless..

would this be a good time to grab 2 used keys, and the four locks and get car back to RCL? I know/guess i will lose alarm but not sure it works anyway.. or am i opening a worm can?

[RichardW]

Be careful John - you can't code a used key to the immobiliser, the chip is a one shot job. Not sure where the chip is, and whether changing the blade over will move the chip over? But then you haven't got any blades that will fit a Std Key. I have recently found a supplier for new keys for our C4 on e-bay, (£30 uncut), so I am going to buy one as we have manged to lose the spare

[jgra1]

right ..didnt know that, many thanks rich.. so looking at two new keys and either a bodge for my blades or get new keys cut and then programmed..

[Bandit12]

Hi John

I used this guy for replacement keys with transponder for about £20. Each key has a shiny new unprogrammed chip which you then program to the car with your lexia.

http://www.carkeyhelp.co.uk/" onclick="window.open(this.href);return false;

I emailed him photos of the key with my digi camera and he cut a perfect copy from them

hope that helps

[jgra1]

thanks bandit.. guessing they are service keys not RCL keys?
would be nice to have remote locking..

[RichardW]

http://www.ebay.co.uk/itm/GENUINE-CITRE ... 369wt_1397

Seller that has the keys for C4 doesn't have C5, but I found this one. Is used, but has a new blade - worth asking the question if the blade renewal has included a new chip? Could be a steal....

PS £85 uncut from Citroen

[Hell Razor5543]

Various people have tried second hand keys, and they have not worked. It seems that the chip (NOT the blade) is a one shot unit, and once it is coded that's it.

[jgra1]

what about this chaps?

http://www.ebay.co.uk/itm/New-Peugeot-C ... 2ece02f1af

[RichardW]

Looks like the thing John....

[myglaren]

I'll let you buy it John and see how it goes and if it's OK I'll have one as well, only got one key for mine and far too mean to go to the dealers for one.