Vectra 2002 2.2 DTI when the door is shut the warning indicator remains on stating that the door open when it's not in turn this is preventing me from locking the doors?

The issue with your Vectra 2002 2.2 DTI, where the warning indicator stays on despite the door being shut, is likely due to a faulty door switch or a wiring problem. The door switch may be stuck or malfunctioning, preventing it from recognizing that the door is closed. Inspect the door latch and switch for any debris or damage, and consider testing the switch with a multimeter. If necessary, replacing the door switch should resolve the warning light issue and allow you to lock the doors.