C5 wount start (go into go into energy saving mode)

[Mark4321]

Hi guys

I need a little help with my C5. 2001 diesel automatic.
NB! I have only backup key (key without buttons).
When I plug the key in ignition and turn it then the display says "go into energy saving mode" and goes black... Sometimes it shows more messages "anti-theft faulty" "gearbox faulty" "abs faulty" etc. and screens goes black.
Starter works but car would not start.

It seems that maybe the key is not being recognised or something like that.
I installed new battery but still same problem.
Cant do diagnostics because energy saving modes disables almost everything.

what can I do?

or how can I set the gearbox on neutral for transport to car to service?

[xantia_v6]

Economy mode does not affect any engine or transmission functions, and does not prevent diagnostics of the engine, so it seems that there is something else going on.

When you turn on the ignition does the immobiliser light come on and then go off? Do you know if the same key has ever successfully started the car previously?

[Mark4321]

Economy mode does not affect any engine or transmission functions, and does not prevent diagnostics of the engine, so it seems that there is something else going on.

When you turn on the ignition does the immobiliser light come on and then go off? Do you know if the same key has ever successfully started the car previously?

Here is a video .. https://1drv.ms/u/s!AqyXZCRfu2UUjbV_K-E ... w?e=ypfabg

Yes ... car has started with this key without any problems. Problem occurred after when car stood few days with empty battery. After that the battery was recharged ... didnt start then ..and after that I replaced it with new battery, but still same problem.

[GiveMeABreak]

First of all I suggest you follow this guide to disconnect and then reconnect the battery - if the vehicle battery was completely discharged, and you have not followed the procedure, some of the ECUs could well need resetting. Follow the relevant parts (skip the parts for Stop & Start vehicles and those parts for vehicles with batteries in the rear).

Make sure you follow the timings correctly.

Before you start, remove the key from the ignition completely so the transponder is well away from the ignition barrel and leave the car for 5 minutes before you start the procedure in case it has gone into anti-scanning mode.

BSI Reset / Battery Disconnect / Reconnect Procedure