15 Jun, 15

BMW CAS3 Immobiliser Module Repair

BMW 5 Series CAS3 Immobiliser Module TestingBMW CAS3 (Car Access System) Immobiliser ECU Repairs
Are you having ignition problems? Does your BMW vehicle not start? If so, this could be due to an issue with your CAS immobiliser module.

The CAS immobiliser module (transponder box) serves as an antitheft alarm system and enables the start of BMW vehicles. Within each vehicle key there is an integrated transponder chip, and a coil ring which 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. When your key is inserted in to the ignition, the transponder in the key is powered via the loop antenna, and key data is 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. Only if they match, is the fuel injection released allowing the car to start.

Common faults associated with the BMW CAS3 Immobiliser module
As mentioned above, some of the issues that you may encounter if you have a problem with your BMW CAS3 module are:

  • Immobiliser Fault Codes
  • No Communication with CAS3 Module
  • Vehicle Won’t Start
  • Key Not Recognised

Most workshops will advise to replace the immobiliser module 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 CAS3 module and the unit must be programmed.

CAS3 Immobiliser Module Repairs – By Sinspeed
Here at Sinspeed, we’re able to fully test and repair the BMW CAS3 immobiliser module using new genuine OEM components and uprated components where possible to ensure each and every repaired BMW CAS3 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 CAS3 Immobiliser fault, give us a call today on 0203 815 9441.

68 thoughts on “BMW CAS3 Immobiliser Module Repair
  • Hi. I’m having trouble with a cuatomers r56 mini cooper s and the red steering lock issue. All the usualthings have been checked and good. Battery, alternator, steering lock. It even has a bypass module fitted. Intermittent red light still popping up. Permanent fault codes in cas module are A0B5 (Road speed signal fault) and A118 (Road speed signal implausible). The codes clear after an elv reset but come straight back after 30 seconds. Eventually it will log fault code A0AA (control module fault) and will lock out the ignition hence no start. Any ideas how to proceed. Thanks

    • Hello Sultan

      Thank you for your enquiry,

      We have sent you an email with full details and pricing.

      Kind Regards


  • Hi we have a bmw x5 E70 that is showing faults that the cas is not communicating with the gear box or transfer box. the vehicle engages the starter motor momentarily, but not long enough to start the vehicle. if we put a live to the starter motor it will start and run is this something yo think you can fix?

    • Hello David

      Thank you for your enquiry,

      We have sent you an email requesting some more details from you.

      Kindest Regards


  • We have a BMW E91 that cranks but no start. For a while the fuse for the remote locking kept blowing until we only used the physical key to open the car. The car recognises the key as it shuts off the alarm but the car only cranks without starting. We have plugged in the car as i thought it might be a sync error as the battery went bad, but we could not sync the cas/dde as it would not allow communication. I have checked the pcb in the CAS and nothing seems out of place (Diode was not blown etc). But, still have the same situation. Can you help with this I.E. check the DDE and CAS? Thanks.

    • Hey Brett!
      Thanks for reaching out.
      Your enquiry has been forwarded to the relevant department & they will contact you soon via email.


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