BMW owners often encounter electrical gremlins that trace back to a failing CAS (Car Access System) module. Whether you’re driving an E-series with a CAS3 module or an F-series with CAS4, understanding the symptoms, common fault codes, and reliable repair options is key to getting your vehicle back on the road quickly.
In this guide, we’ll walk you through the most frequent issues related to BMW CAS module repair, what they mean, and how to fix them—without overpaying at the dealership.
What is the BMW CAS Module?
The CAS (Car Access System) module controls key authentication, start authorization, and anti-theft functions. When it fails, your vehicle may not crank, communicate properly with the DME/ECU, or allow key programming.
BMW has used several generations of CAS, with CAS3 common in E90, E60, E70, and other E-series vehicles, and CAS4 found in newer F-series models like the F10, F01, and F15.
Common BMW CAS3 Issues and Fault Codes
If you own a BMW with a CAS3 module, here are some common failure symptoms:
- No crank/no start
- Key not recognized
- Loss of communication with DME
- Intermittent starting issues
- “Key Not Detected” messages
Typical CAS3 Fault Codes Include:
- A0C1 – CAS: Start authorization
- A0AD – CAS: No communication with DME
- A0AA – CAS: Control module fault
- A0B4 – CAS: Key authentication error
🔧 Solution: Our BMW CAS3 Repair and Clone Service restores your original data and syncs it with the DME to bring your BMW back to life. Whether your module is dead, corrupted, or bricked during a failed programming attempt—we can help.
Common BMW CAS4 Issues and Fault Codes
CAS4 modules are more secure and sophisticated, but that also makes them more fragile to voltage spikes, battery swaps, or improper programming. Common signs of failure include:
- Complete loss of ignition
- Keyless entry malfunction
- Vehicle won’t start after a jump or module update
- No communication with diagnostic tools
Typical CAS4 Fault Codes:
- D900 – CAS: Internal fault
- D908 – CAS: EEPROM error
- D90D – CAS: Fault in processor
- 8040A9 – CAS: Fault, central gateway timeout
🛠️ Solution: Our BMW CAS4 Repair and Restore Service includes data recovery, ISN sync, and cloning if needed. We handle both bench and mail-in repairs.
✅ Restore your CAS4 module today »
Why Choose Ecumedics for BMW CAS Module Repairs?
- ✅ Extensive experience with BMW CAS3 & CAS4
- ✅ Repair, clone, or restore options
- ✅ Support for lost keys, water damage, and bricked modules
- ✅ Fast turnaround and mail-in options
- ✅ Secure data handling with original ISN preservation
Need Help Diagnosing Your BMW?
If you’re unsure whether your issue stems from a CAS module failure, we’re here to help. Use our contact form to describe your symptoms, upload fault codes, or get a custom quote.
📞 Contact our BMW CAS specialists now »
Don’t let a faulty CAS module cost you thousands or leave you stranded—repair your BMW the smart way.