U0120
Lost Communication with Starter/Generator Module
2006-2011 BMW 325i 3.0L I6 N52 🇩🇪
Moderate SeverityNetwork
Description
Cannot communicate with the integrated starter-generator in start-stop or mild hybrid vehicles.
Symptoms
- Start-stop system disabled
- Engine will not auto-restart
- Mild hybrid assist not available
- Warning message displayed
Common Causes
- Starter-generator module failure
- CAN bus wiring
- Module power loss
- Belt-driven starter-generator fault
Diagnostic Steps
- Check module fuse
- Test power and ground
- Check CAN wiring
- Test starter-generator operation
- Inspect drive belt condition
Repair Notes
Check power supply and belt condition on belt-driven starter-generators.
Related Codes
Other Network Codes
- U0001High Speed CAN Communication Bus
- U0002High Speed CAN Communication Bus Performance
- U0003High Speed CAN Communication Bus (+) Open
- U0004High Speed CAN Communication Bus (+) Low
- U0005High Speed CAN Communication Bus (+) High
- U0006High Speed CAN Communication Bus (-) Open
- U0007High Speed CAN Communication Bus (-) Low
- U0008High Speed CAN Communication Bus (-) High
- U0009High Speed CAN Communication Bus Shorted Together
- U0010Medium Speed CAN Communication Bus
U0120 on Other Vehicles
Common Questions
What does code U0120 mean on a 2006-2011 BMW 325i?
U0120 stands for "Lost Communication with Starter/Generator Module". Cannot communicate with the integrated starter-generator in start-stop or mild hybrid vehicles.
What are the symptoms of U0120 on a BMW 325i?
Common symptoms of U0120 include: Start-stop system disabled, Engine will not auto-restart, Mild hybrid assist not available, Warning message displayed.
What causes U0120 on a 2006-2011 BMW 325i?
Common causes of U0120 include: Starter-generator module failure, CAN bus wiring, Module power loss, Belt-driven starter-generator fault.