🔧 BMW won’t start, despite a healthy battery and working key?
⚠️ Fault code A0C1 stored in the CAS control module?
🛠 ECU Fix offers reliable CAS3 repairs for BMW A0C1 faults—no coding needed, lifetime warranty included
If your BMW refuses to crank or start and your diagnostic tool flags BMW A0C1 – CAS Output, Terminal 50, you’re likely dealing with a failing CAS3 immobiliser module. This is a known issue on a range of BMW models built between 2006 and 2013.
The A0C1 fault typically appears after intermittent starting issues, eventually resulting in complete no-start. At ECU Fix, we provide fast, professional CAS3 module repairs to permanently resolve the A0C1 fault without the need to replace or reprogram anything.
🔍 What Does BMW A0C1 Mean?
The A0C1 code indicates an internal malfunction of the Car Access System (CAS). This module manages start authorisation, key recognition, and the relay signals that activate the starter motor.
When the internal circuitry of the CAS3 module begins to fail, it can no longer reliably send power to the starter system—resulting in a no-crank condition, even though all other systems appear normal.
⚠️ Other Commonly Linked CAS Fault Codes
In addition to BMW A0C1, your diagnostics may show:
- A0B4 – Starter Operation, Terminal 50 Off
- A0B0 – Starter Operation, Terminal 50 On
- A0B5 – Starter Operation, Terminal 50/50E Off
- A116 – Supply Voltage Terminal 30 Too Low
These codes further support an internal fault in the CAS3 module, often pointing to failed switching relays or voltage pathways.
🚫 Symptoms of BMW CAS3 A0C1 Failure
When the BMW A0C1 fault is present, you may experience:
- Complete no-crank when pressing the Start/Stop button
- Keys are recognised, but the starter motor doesn’t engage
- Fault codes reappear after clearing
- EPS and dashboard systems power up normally
- All relays, fuses, and battery voltages test fine
These are tell-tale signs that the CAS3 module is no longer switching Terminal 50, and a repair is needed.
🛠 How ECU Fix Repairs BMW A0C1 Faults
We provide an in-house repair solution for the A0C1 fault that restores full functionality without reprogramming.
Our service includes:
- Thorough testing of CAS module power and signal circuits
- Replacement of failed relays, ICs, or voltage regulators
- Validation of Terminal 30 and 50 logic
- Simulated engine-start testing to confirm function
- Return of unit ready to refit—no coding or key programming required
- All repairs include a lifetime warranty
We eliminate the A0C1 fault at its root, restoring normal starting operation permanently.
BMW CAS3 Repair Service – None start
🚗 BMW Models Affected by A0C1 CAS Faults
We frequently repair BMW CAS3 A0C1 issues on:
- BMW 1 Series (E81, E82, E87, E88)
- BMW 3 Series (E90, E91, E92, E93)
- BMW 5 Series (E60, E61)
- BMW X1, X3, X5 (E70, E83, E84)
- BMW Z4 (E89)
- Mini Cooper (R56, R57, R58, R60) – with CAS3 systems from 2007–2013
- Other BMWs fitted with CAS3 modules (2006–2013)
If your vehicle shows BMW A0C1, we can help you avoid costly replacements and get you back on the road.
Part numbers of affected CAS modules include:
- 6135926760901 / 6135928753502 / 6135914722001 / 6135923704701 / 6135922623801 / 6135694383401 / 6135914719501
⚙️ Why Choose ECU Fix?
- ✅ Specialist CAS3 module repairs
- ✅ Lifetime warranty on all successful repairs
- ✅ Fast 24–48 hour turnaround
- ✅ No coding or key programming required
- ✅ UK-wide courier collection available
- ✅ No fix, no fee—you only pay collection & return shipping if unrepairable
We’re trusted by garages, BMW owners, and auto electricians nationwide.
📦 Book Your BMW A0C1 CAS3 Repair Today
- Click “Shop Now” to start your booking
- Choose courier collection or post the unit directly
- We test and repair the CAS3 module
- Refit and restart—no reprogramming required