if key fob battery out for some time it will need to be reprogamed to the car again, some models just need to put key in and turn to 2 and press button on key fob to rest. older models need tec2 to re-do the code.
Russell hill, July 2010
When you opened the key to remove the battery the immobiliser chip may have fallen out.
If the engine management light is flashing when you crank the engine this would suggest an immo problem.
Do you have a spare key you can try?
