In this guide, we take a look at how to troubleshoot BMW CAS module (Car Access System) using an OBD-II diagnostic scanner. You will learn what CAS module does, what systems it covers and how to read/clear codes from BMW CAS module.
What is BMW CAS module?
CAS stands for Car Access System. Two of the main functions of BMW CAS module include enabling the vehicle to start and monitoring the anti-theft alarm system. CAS module generates random key code every time the vehicle is stared and synchronizes the code with the Engine Control Unit which BMW calls DME or DDE.
When a defective BMW CAS control unit is replaced, it needs to be programmed if the module is new (virgin). If a used BMW CAS module is installed the Engine Computer (DME) and key need to be replaced as well with those from the donor car.
BMW CAS Module Location
BMW CAS module is located under the steering column. To remove the BMW CAS module, you will need to get under the dashboard on the driver side, remove the plastic cover under the dashboard (above the brake and gas pedal). Once you remove the panel you will find your BMW CAS module which will be a black or white box.
When replacing BMW CAS module it needs to be programmed and synchronized with the DME and car keys.
List of possible symptoms you may notice if the CAS module or one of its components fails.
- Malfunction message on iDrive screen
- BMW does not start
- Key not recognized
- BMW won't start due to bad CAS module
- Car will turn over but not start.
How to read / clear CAS Fault Codes
If you are experiencing problems a good starting point is to read fault codes from the CAS module. If any code is PRESENT it needs to be addressed. If codes are in STORED / PAST status, they can be erased.
What you will need
A diagnostic scanner that is capable of reading, clearing and performing bi-directional tests on BMW vehicles. You must verify that the scanner that you use supports your BMW model and year. Full system scanners that are known to work on BMW vehicles can range in price from $150 to $800 USD.
List of scanners that read and clear BMW CAS fault codes.
- Autel MaxiDAS (Model 808 and up)
- Foxwell for BMW (Model 510 and up)
- Launch Full System Scanner (Model X431 and up)
Other OBD2 scanners allow you to read and clear BMW CAS fault codes. To learn about other OBD2 scanners that work on BMWs check this article on Choosing the best OBD2 scanner for BMW.
- Plug in the OBD-II scanner into the diagnostic port under the dashboard.
- Turn on the ignition, don't start the engine.
- Turn on the scanner and select your BMW chassis. Next, Select Control Units menu.
- Select CAS Module. Once you enter the CAS module, you will be able to do the following.
- Read Codes from CAS Module
- Clear Codes from CAS Module
- Perform Adaptations, Activations, Tests
- Reset CAS Module
This is a list of problems that can trigger fault codes in the CAS module.
Vehicle Will Not Start - A defective CAS module that has been damaged from water or due to low or overvoltage will prevent the vehicle from starting. Replacing the CAS module and programming is necessary to fix this problem.
Mismatched Key - The code in the CAS module may get out of sync with the code stored in the DME / DDE module. To fix this problem carry out CAS reset procedure under DDE/DME module.
Adaptations & Tests in CAS Module
This is a list of test and sensor activations that you can perform via the CAS module.
- Delete electric steering lock fault counter
- Reset CAS module
- Remote control, battery status
In the CAS Module, you can display live data from various sensors that communicate with the CAS module.
- Brake light switch
- Central locking button
- Electric steering lock fault counter
- Status of door contact switches
- Key number
Below are some examples of codes you may see stored in BMW CAS module.
- A082 CAS Supply terminal 30E 30L
- A085 CAS Fault road speed signal
- A080 CAS Output wake up line
- 2F44 EWS preventing manipulation
- A103 -- CAS: immobilizer bus fault (in CAS)
- A0B2 Supply, terminal 30E
- 4a63 BMW Fault Code – EWS Tampering or EWS Manipulation
- CAS 14 Door Open F/R
- CAS 15 Door Open F/L
- CAS 16 Door Open R/L
- CAS 17 Door Open R/R
- CAS 18 Bonnet open
- CAS 19 Boot open
- CAS 21 Ignition Problem, Depress Brake to Start
- CAS 22 Starter Problem, Engine cannot Restart
- CAS 38 Wrong Remote Key
- CAS 40 Press Brake to Start
- CAS 65 Change Key, Key Battery Low
- CAS 66 Remote Control/Key Fault
- CAS 67 Remote Control/Key Battery Discharged
- CAS 68 Remote Key Stationary Function Battery Low
- CAS 186 ELV Steering Lock Fault. Engine cannot be restarted
- CAS 187 ELV Steering Lock Active. Move Steering Wheel to Restart
- CAS 205 Remote Key not Present
- CAS 206 Engine Start on next Press
- CAS 208 Comfort Access Deactivated
- CAS 209 Remote Key in Vehicle, Locking not possible
- CAS 217 No Remote Control
- CAS 303 Depress Clutch to Start
- CAS 335 Ignition Switched On
- CAS 347 Position R/N/D Not Possible
- CAS 348 Engage Park Before Leaving Vehicle
- CAS 349 Engage Park Before Switching Ignition Off
- CAS 413 Steering Column Unlocked
There are hundreds of fault codes that can be saved in BMW CAS module.
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