Immobilizer

i disconnect the batt of my a3 and when i re connect ignition not turning on and cd player display showing {safe] mode my car is a3 2005 1.6 fsi sport

Why is your post header “Immobilizer”? Not all us (me) know what a “a3” is. Post this for the less “hip”. I know Audi had a model A4 is this a clue?

Give a description about what does or does not happen when you turn the key (normal warning light activity,cranks in “start” position,that kind of stuff) I would think the CD player/radio would come up in a “locked” configuration after battery disconnect,“safe” mode has me wondering.

Tell us about security system,factory or aftermarket,with remote,does it have a “valet” mode?

I believe the A3 referred to is a VW but I don’t know about the fsi sport , I believe it is a Touareg, I would guess that is a European model.

Check the owner’s manual.