BMW CAS or EWS fault: key not recognised, no start
On BMWs and MINIs of the E-series era, the CAS (Car Access System) or older EWS box stores the key data and the code the engine ECU expects. When it fails, the car won't recognise the key.
Symptoms
- Key not detected, no crank, or starter works but engine won't fire.
- Central locking or key buttons stop working (CAS).
- Problems after water ingress or a battery fault.
Checks first
- Try the spare key — a key fault is more common than a CAS fault.
- Battery voltage and CAS power and earth.
- Water in the driver's footwell, where the CAS often sits.
Our service
- For supported CAS and EWS versions, we transfer the key and vehicle data from your original unit into a matching donor. The version is identified by the chip mask code, which we confirm before you post.
- We ask for proof of ownership, and we never remove or bypass the immobiliser.
Questions
Which CAS versions do you do?
Only the versions listed on our immobiliser page. Send a label photo to check yours.
Need it checked?
Send your part number and a label photo — we'll tell you whether it's a repair or a clone, and the price, before you post.
Related services
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from £58.50General guidance only — always diagnose the vehicle properly.