urgent help . immobiliser fault

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jgra1
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urgent help . immobiliser fault

Post by jgra1 »

chaps, just driven from oxford to Kent, got within 3 miles of home and decided to shop.. back to car and immobilser fault coming up when I tried to restart..

have only one key for car, although another one 10 miles away in a barn, I hope.,.

tried locking / unlocking car. took key apart and tried to get another battery but none for sale (key is non fob style but does have a battery in it - aftermarket)

did a (fast) soft reset, nothing..

have lexia here for as long as laptop battery lasts,.. anything I can try? - or should I try spare (service) key

or AA?

John, thanks for any /quick/ help
deano1970
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Re: urgent help . immobiliser fault

Post by deano1970 »

is it turning over ok?? I have a C5 which had a dodgy battery and a few times I got "anti theft device faulty" in the display.....I put a new battery on it and it cured it?? best I can offer........good luck
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Re: urgent help . immobiliser fault

Post by Mandrake »

jgra1 wrote:chaps, just driven from oxford to Kent, got within 3 miles of home and decided to shop.. back to car and immobilser fault coming up when I tried to restart..

have only one key for car, although another one 10 miles away in a barn, I hope.,.

tried locking / unlocking car. took key apart and tried to get another battery but none for sale (key is non fob style but does have a battery in it - aftermarket)
Any battery in the key won't be relevant to an immobiliser fault as the immobiliser uses an RFID style tag which is powered by the induction loop in the pick-up antenna on the ignition barrel - eg no batteries required.
did a (fast) soft reset, nothing..

have lexia here for as long as laptop battery lasts,.. anything I can try? - or should I try spare (service) key

or AA?

John, thanks for any /quick/ help
Have you checked the car battery voltage ? As deano says low voltage from a failing battery can bring up all kinds of weird faults on a C5 including immobiliser failure, so the most likely cause is your battery has died.

If you don't have a volt meter to check the battery voltage you could try using the Lexia to get a battery voltage reading - if you can establish communication with the engine ECU you should get a battery voltage reading from there.

You could also use the Lexia to read the fault codes from the BSI which should have a code explaining why the immobiliser failed - for example "unable to read key identity" or similar...

But definitely check battery voltage first and get a jump start if necessary - if it starts ok with a jump start you know its a battery problem...
Simon

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Post by addo »

I'd even try wiggling the antenna plug into the COMM unit.
jgra1
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Re: urgent help . immobiliser fault

Post by jgra1 »

thanks all

um

'Any battery in the key won't be relevant to an immobiliser fault as the immobiliser uses an RFID style tag which is powered by the induction loop in the pick-up antenna on the ignition barrel - eg no batteries required.'
Simon, wonder what the battery does then? just curious? no buttons.. just a circuit board and a 3v battery...

well.. went and got spare key, the service key.. was greeted by the whole roof including timbers missing from the storage barn,.. I had to smile at that.,. :) been an interesting xmas already... will deal with that tomorrow..

spare key the same... bashed my hand on the fusebox area as I was beyond caring.,,



yep.. that was that :) got home fine.. albeit a few hours later...

realised I had the same problem a year ago.. something gets loose in there and the immob warning comes up..

so, thanks for all pointers.. if in doubt, and the lexia wont help, hit areas of electrickery and you culd get lucky :)
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Post by addo »

Bugger, eh. Hopefully someone warm and sympathetic will seek you out tonight...
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