So, as my old bmw style key looked a bit ragged I went and bought a case (ie blade/black moulding bit etc but no transponder) and duly had that cut to match my old key. Fitted the transponder from the old key and hoped for the best. Transponder obviously works fine and the key will unlock the doors but won't turn the ignition no matter how much jiggling etc.

Have I missed a step or made some other schoolboy error?

When you stick the key in or even when it comes close to the ingnition lock, you will hear the unlocking sound of the steering lock. That is the indication that the transponder is working or not. If you can't turn the key in the lock anyway, the cutting of the blade would be the most likely culprit here. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Try holding the new key close to the ignition switch (it should click)and use the old key in the lock.

If it works the new key cut is naff.

(I think) !!

Cheers

RP

Could be a bad cut in the new blade. I bought 2 flip keys and had them cut at a recommended cutter and neither would turn the ignition although they opened the door fine. I ended up hacking the blade out of a one of the old keys and fashioning to fit one of the flip key which works ok as a bodge. I was told that as my ignition was old (95K vehicle) the lock had probably worn so the newly cut key would not work. There is a difference between knowing your sh!t and knowing you're sh!t

2005 Registered 2006 MY 4.4 AJV8 Range Rover Vogue

Are you sure you moved the transponder over from the old key to the new key ie the bit of black plastic about the size of a couple of grains of rice that lives in the bottom of the case?

Sounds like the transponder is not being seen by the car and not unlocking the steering lock and ignition, leave the new key in the ign and hold the old key case close to the ignition barrel/hole and see if it will turn then, if it does you have left part of the important gubbins in the old key! If it doesn't work with the old key case try holding the spare close, if it works then you Fubard something when swapping the immards over.

If neither work the key cut is rubbish. There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
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2010 LR D4 Commercial 2.7 TDV6

To see if it is the key or the transponder put the new key with the transponder next to the ignition it should click and unlock the steering lock. Then with the new key next to the ignition (must be right next to it and do not remove) try the old key. If the old key starts then the cut on the new key is the problem. There is a difference between knowing your sh!t and knowing you're sh!t

2005 Registered 2006 MY 4.4 AJV8 Range Rover Vogue

OK after a few request i have found some one who will cut keys and guarantee they work, i popped over there to have a couple of vw keys cut for my daughters new car, now this man as crazy as it sounds can cut your key from a photo and post it to you .i do remember someone talking about using this service but never forwarded any info..he also has spare blanks for the flip keys,
when it comes to having keys cut there is a thin line between working and not,just because it fits the door and unlocks it still might have trouble in the ignition,..i have come across this dozens of times,
with ref to your transponder as i has been said,listen for the click when the key comes close to the ignition,about 25mm
but it sounds like a duff cut,
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Well, thats yet another result for the forum - problem fixed. I would have never noticed that tiny little block of plastic which looked like part of the moulding. Swapped that over and jobs a good un - I thought the pcb was the transponder, and I was wrong.

If you're in Falmouth and need a key cut - there's a lovely old fella on the high street, did it in 10 mins.

Cheers Guys.

You're not the first to miss that innocuous but important little piece of plastic when changing key cases.
It's even worse if you throw it away.

Result👍 There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
Fiat 500x 1.4 multiair Lounge 2015
2010 LR D4 Commercial 2.7 TDV6