Car turning over but won't start?

First things first. If the car battery is good and the engine is turning over as normal (sounds normal?) - look at the instrument cluster. If the orange engine management light is flashing, you have an immobiliser issue. It only ever flashes for an immobiliser issue.

Vectra B, Astra G and Zafira were very prone to the key and the remote fob separating -either when in the ignition barrel or even just when somebody is playing with the keys. If they get separated, a tiny plastic transponder chip can drop out of the key and the immobiliser will no longer recognise it.

Very often I've been out to a non-starting car, only to find the chip sat on the mat in the footwell. It's black, just under a centimetre long and slightly wedge-shaped. On later keys they glued the chip in to prevent this.

If this happens on any other model, try your spare key. Transponders sometimes go down and you will need a new one programmed to the car. A locksmith or Vauxhall dealer will be able to do this.

Astra H models required a software update to cure this issue. This will need to be done at the dealer and most would have been cured under warranty by now.