06/09/2026
BMW E87 All Keys Lost – When Two New Keys Still Don’t Work 🔑
A local locksmith contacted us after really struggling with a BMW E87 1 Series in an all-keys-lost situation.
He originally came to us because he needed the ISN from the engine ECU and was struggling to extract it himself.
For anyone wondering what that means, the ISN is essentially a secret security code shared between the BMW's engine ECU and immobiliser system. In an all-keys-lost situation, you will generally need to obtain this information from the vehicle so that a new key can be correctly programmed and authorised.
If you're simply adding a spare key while you still have a working original, the process is different because the necessary security information can normally be obtained using the existing key. But with all keys lost, you don't have that original key to work from, which is why obtaining the ISN becomes an important part of the job.
We extracted the ISN from the ECU for him, and he went away and programmed a new key to the CAS3. With the correct ISN, this is normally a relatively straightforward process.
The new key programmed in and the remote central locking worked perfectly. However, when the key was pushed into the dashboard key slot, the ignition wouldn't come on.
He tried a second new key — exactly the same problem.
When we carried out our own testing, everything on screen looked correct. But when we tested his key directly with the CAS on our test rig, the CAS wasn't correctly recognising the key when it was inserted, even though the remote locking and unlocking functions were working.
That raised one important question:
Were both keys from the same batch?
The answer was yes.
Although he'd tried two different keys, both were from the same batch of aftermarket keys he'd purchased online. So changing the key hadn't actually ruled out a faulty batch.
We then programmed one of our own high-quality European-sourced keys to the CAS3.
Remote locking worked. Key recognition worked. Ignition came on. Everything perfect. ✅
The locksmith hadn't done anything wrong. The ISN was correct, the programming procedure was correct and he'd even done the sensible thing by trying another key.
The problem was simply poor-quality aftermarket keys.
It's a good lesson for anyone doing vehicle key programming: trying two keys doesn't necessarily rule out the key when both came from the same batch.
Sometimes the cheapest part of the job can cause the biggest headache!
