U0118
Lost Communication with Alternator/Generator Module
2019-2024 BMW 3 Series G20 2.0L I4 Turbo B48
High SeverityNetworkGeneric (SAE)
Description
Cannot communicate with the smart alternator or integrated starter-generator module.
Symptoms
- Battery warning light
- Charging system malfunction
- Battery not charging
- Voltage fluctuations
- Stop-start system disabled
Common Causes
- Smart alternator failure
- CAN bus wiring to alternator
- LIN bus issue
- Alternator connector corrosion
- Voltage regulator failure
Diagnostic Steps
- Check alternator fuse
- Test alternator output voltage
- Check CAN/LIN wiring to alternator
- Inspect alternator connector
- Test alternator with direct command
Repair Notes
Modern smart alternators communicate on CAN or LIN bus. Check wiring and connector at alternator.
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
U0118 on Other Vehicles
Common Questions
What does code U0118 mean on a 2019-2024 BMW 3 Series G20?
U0118 stands for "Lost Communication with Alternator/Generator Module". Cannot communicate with the smart alternator or integrated starter-generator module.
What are the symptoms of U0118 on a BMW 3 Series G20?
Common symptoms of U0118 include: Battery warning light, Charging system malfunction, Battery not charging, Voltage fluctuations, Stop-start system disabled.
What causes U0118 on a 2019-2024 BMW 3 Series G20?
Common causes of U0118 include: Smart alternator failure, CAN bus wiring to alternator, LIN bus issue, Alternator connector corrosion, Voltage regulator failure.