No.
You're OK so long as you have a working remote-fob OR if you don't have one, you're sure you know the immobiliser code.
After re-connecting the car battery, you'll have to re-synchronise the car to the fob(s) by pressing the Lock button FOUR times quickly.
It's also useful to check whether you do know the correct immobiliser number - but only do this if you have a working fob that lets you drive the car at present. Lock the car with the fob. Unlock it the key and open the driver's door - you should see the immobiliser LED illuminate on the dash and the engine can't be started. Remove key from ignition and close driver's door. Go through the immobiliser over-ride procedure using the code you (think you) know! If it's the correct 4-digit code, when you next open the driver's door, the LED will stay off and the engine can be started. If it wasn't, you can recover use of the engine by closing the car's doors, then locking and unlocking it WITH THE WORKING FOB.
The immobiliser isn't vindictive - it'll always let you "recover" use of the car if you've entered an incorrect code manually - so long as you have a valid working radio-fob. After this process, you'll have ascertained if the immobiliser code you have, is the correct one!
StoppingService, November 2007
