Xsara Immobiliser Problem

[county2000]

Hi Guys,
Posted this earlier as a reply to my Xsara Starting Problem thread but thought I'd give it it's own thread.
Basically I disconnected the battery last Sunday to remove a dodgy starter motor, fitted a spare today and reconnected the battery.
But now the immobiliser warning light comes on and the red LED on the hazard button is on permanentlly. I have pored through forums looking for a fix and have tried several to no avail. The battery is charged, I have tried leaving the ignition on for an hour, pressing the remote locking button, etc etc. Incidentally the remote locking doesn't work either. The owners manual states that if the car is not being used for a month or two, to disconnect the battery, so there must be some way to reset the immobiliser without a tow to the dealers surely. To make matters worse, I wound down the drivers window for easy access and now Eco Mode has come on and I can't wind it up again.
Apologies for being long winded but can anyone help?

Dai

[county2000]

Problem sorted. Had to call out mobile locksmith to reprogramme keys.
Question - how long can you leave the battery disconnected before it becomes a problem?

Dai

[spider]

As far as I am aware, in theory more or less indefinitely as the ECU should not lose the code ever as its probably stored in a PROM.

I realistic life with no battery at all is 3 years or so, but I am speculating on the method of code storage...

[wheeler]

If the keys lost there code it was probably due to not following the correct battery disconection procedure. The BSI needs to be fully shut down which takes about 3 minutes after the ignition is switched off, during this time you must not activate anything electrical on the car or open/close any doors as theese things can 'wake' the BSI back up. The battery should only be disconnected once it has fully shut down otherwise you get problems like you had. It's a bit like just unplugging the power on your computer to shut it down.