U0118high severityNetwork
Lost Communication with Alternator/Generator Module
on 2017 Subaru Legacy 2.5L H4 · AWD
What this code means
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.
Other Network codes on this vehicle
U0001
High Speed CAN Communication Bus
U0002
High Speed CAN Communication Bus Performance
U0003
High Speed CAN Communication Bus (+) Open
U0004
High Speed CAN Communication Bus (+) Low
U0005
High Speed CAN Communication Bus (+) High
U0006
High Speed CAN Communication Bus (-) Open
U0007
High Speed CAN Communication Bus (-) Low
U0008
High Speed CAN Communication Bus (-) High
U0009
High Speed CAN Communication Bus Shorted Together
U0010
Medium Speed CAN Communication Bus