Engine turning but not starting. Quick tip

Just had an interesting fault.
I bought some new cases for my keys as the buttons had broken on them.
I fitted the original key and checked the doors unlocked, but later when I went to use the car it would turn but not start.

After a lot of hair pulling I found that embedded in the body of the original key case is a small rectangular black chip about a cm by 6mm and with no legs so it looks just like a piece of plastic.

It appears this is what triggers the immobiliser and allows the engine to start, so make sure you transfer this chip over as well as the key blade its self if you buy any of these key cases.
Regards John

Thanks, it's the immo chip and there are pictures of the chip and the fob in this fob fix topic.

Without a paired immo chip you can't get past the immobiliser and the injectors won't let fuel pass.

Thanks Arfur,
when I had the fault, I thought it was an engine problem and initially didnt think of the key fob so only searched for an engine fault.
It was only when getting desperate that I retraced my steps with the key fob.
The Haynes I have did not mention the chip so I didn't think.

Thanks for your reply.
Regards John