15 Jun, 15

BMW CAS2 Immobiliser Module Repair

CAS2 Immobiliser Module FaultsBMW CAS2 (Car Access System) Immobiliser ECU Repairs
Have you been having issues with your BMW not being able to start up? Vehicle key not working? If so, it could be due to a fault with your BMW CAS2 Immobiliser module.

The CAS immobiliser module (transponder box) enables the start of your BMW vehicle, as well as acting as an antitheft alarm system. A transponder chip is integrated within each vehicle key, and a coil ring is fitted around the ignition lock. The transponder chip is powered by this coil from the CAS module, meaning that no battery is necessary within the key. Inserting the vehicle key in to the ignition causes the transponder in the key to be powered via the loop antenna, allowing key data to be sent to the CAS control module. If the key data is correct, an enable signal is then sent to the starter and the CAS module then sends the random code to the Engine Control Module (DME / DDE) where the random code is checked against the saved random code. If both codes match up, the fuel injection is released allowing the car to start.

Common faults associated with the BMW CAS2 Immobiliser module
When issues arise either with the CAS2 Control module or in the key, it can cause any of the following faults to occur:

  • Immobiliser Fault Codes
  • No Communication with CAS2 Module
  • Vehicle Won’t Start
  • Key Not Recognised

Unfortunately, if you wish to replace the immobiliser module, most workshops will advise to replace the whole unit because they are unable to repair it. It’s not possible to replace them with a second hand part because the unit will be locked to the vehicle it came from and unless you’re buying a complete immobiliser kit, you will require a new CAS2 module and the unit must be programmed.

My CAS2 Immobiliser Module is Faulty – Can Sinspeed help?
Here at Sinspeed, we’re able to fully test and repair the BMW CAS2 immobiliser module using new genuine OEM components and uprated components where possible to ensure each and every repaired BMW CAS2 ECU is rebuilt to meet & exceed OE specifications. All remanufactured units are returned with a Lifetime warranty and will not require programming.

If you have a BMW CAS2 Immobiliser fault or require a diagnosis, give us a call today on 0203 815 9441 where we will be happy to help!

4 thoughts on “BMW CAS2 Immobiliser Module Repair
  • Hi, we are a mileage correction company, and have a 2005 BMW 120D CAS2 unit which one of our new programmer has read wrong or mis-soldered somewhere, we are unable to see what is wrong with it, when inserted back into the vehicle there is no difference as to if not inserted, nothing is operational, I believe something within the circuitry is wrong or perhaps burnt out, if we send it in, can it be repaired?

    Kind Regards

    • Hi John / Tony

      Thanks for the enquiry,

      We can definitely take a look at it for you, however it is always difficult to work with a unit that has been previously opened and worked on. I have sent over an email with some pricing and information as a guide line.

      Kind Regards


  • hi,
    wondering if you can point me in the right direction, (bmw E90 3 series m sport 318D car wouldn’t start, cranks over but that’s it. )

    I have had an issue with my ecu which suffered water damage, it was sent away for repair, at which point I was told I would need a new unit. they supplied me with a recon unit and swapped all my data from my old ecu to the new one, when this was sent back to me I was told it was successful and it was plug and play and should start the car up.
    I then had the same issue as before the car wouldn’t start. It was coming up with a EWS tampering fault.

    sent the ecu back to checking and said everything is okay, but still doesn’t work and showing ews tampering fault when plugged in car.

    (the point when my car was off road, I bought a second hand ECU kit, ECU/ cas module/ key plugged this straight in and car started up.)

    swapped all my old units over and new ECU and does work.
    any information you could proved and point me in the right direction would be very helpful

    • Hello Adam

      Thank you for getting in touch,

      We have sent you an email with more details.

      Kind Regards


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