BMW DTC C109B – Brake System Control Module SPI-Bus Communication Error
DTC C109B meaning on BMW
DTC C109B is a fault code that indicates a Brake System Control Module SPI-Bus Communication Error on BMW vehicles. This error occurs when there is a communication problem between the brake system control module and other modules on the vehicle’s SPI (Serial Peripheral Interface) bus.
BMW DTC C109B symptoms
Symptoms of DTC C109B on a BMW may include:
- ABS (Anti-lock Braking System) warning light illuminated on the dashboard
- Brake system malfunction warning message displayed
- Loss of ABS functionality
- Loss of stability control system functionality
BMW DTC C109B causes
The common causes of DTC C109B on BMW vehicles include:
- Faulty brake system control module
- Issues with the SPI bus communication network
- Wiring harness or connector problems
- Software glitches or programming errors
BMW DTC C109B seriousness
DTC C109B is a serious fault code as it affects the communication and operation of critical safety systems such as the ABS and stability control. Driving with this fault unresolved may compromise the vehicle’s braking performance and overall safety.
How to diagnose DTC C109B on BMW
To diagnose DTC C109B on a BMW, a professional mechanic would typically perform the following steps:
- Use a diagnostic scanner to retrieve the fault codes stored in the vehicle’s system
- Inspect the brake system control module for any visible damage or signs of malfunction
- Check the wiring harness and connectors for loose connections or corrosion
- Perform a communication test on the SPI bus network to identify any communication errors
How to fix DTC C109B on BMW
Fixing DTC C109B on a BMW may involve the following steps:
- Replace the faulty brake system control module if necessary
- Repair any damaged wiring harness or connectors
- Update the software of the control modules to the latest version
- Perform a reset or reinitialization of the brake system control module
How to erase DTC C109B on BMW
To erase DTC C109B on a BMW, a diagnostic scanner capable of clearing fault codes is required. The process typically involves:
- Connect the diagnostic scanner to the vehicle’s OBD-II port
- Select the option to clear fault codes from the system
- Follow the on-screen prompts to erase the DTC C109B code
- Verify that the fault code has been successfully cleared by rescanning the system
Recommended tools & DTC Scanners for BMW
Best Diagnostic App for modern BMWs: BimmerLink
Recommended Bluetooth adapter for Bimmerlink: OBDLink CX
Cable adapter for Bimmerlink: Enet Cable USB Type C
For older BMWs we recommend: Autel AutoLink AL319 (2024 version)
Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter
Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.