Car not starting

[Crazyface]

Car fob was needing replacing so I bought a new one to swap the internal bits over. Did this and had to reprogramme jit following a strange sequence of things which worked to open and close the locks but now it won't link to the engine and start.
It's a Mazda 3 2009.
Can anyone help???? Without the obvious....take it to a dealer.

 

[RichA]

Have you still got the old key? I did this with a Ford key years ago. There was a small plastic tab about the size of a match head inside that needed to be transferred to the new key. It was slotted into a recess inside the body. It's the transponder that stops the car being hot-wired.

 

[Bunkermagnet]

Don’t you have to reprogram all the keys?
Do you not have an independent Mazda specialist who could do it for you?
If not I suspect it’s dealer only.

 

[srixon 1]

Have you still got the old key? I did this with a Ford key years ago. There was a small plastic tab about the size of a match head inside that needed to be transferred to the new key. It was slotted into a recess inside the body. It's the transponder that stops the car being hot-wired.

I had the same thing with an Astra. Tiny thing that looks like it is part of the fob casing.

 

[Crazyface]

Have you still got the old key? I did this with a Ford key years ago. There was a small plastic tab about the size of a match head inside that needed to be transferred to the new key. It was slotted into a recess inside the body. It's the transponder that stops the car being hot-wired.

Yup, I have the keys, but no sign of any recesses. It's all a bit wired. The key I have managed to reprogram to open the doors will only lock and unlock the doors when I'm sitting inside the car. The other one is just dead. I wonder if the new battery I installed is now in the wrong fob, I did a lot of messing about. I'll try that.

 

[Crazyface]

Er, er. Well in the process of changing the battery I also swapped the key over, there's two parts to the fob, as the key on the old one didn't spring out and guess what, that's where the transponder was. And it had fallen out. It looks like a bit of plastic that had broken off, but luckily id kept it and after yet another search of the net to maybe buy one, there was a picture of one. I checked all the bits I had and there it was. I popped it back into the housing it should be in and ...VROOOM, we have ignition. Phew! Now it's got to get though it's MOT and I'll get a back up one sorted.