U0118
NetworkModule Communicationhigh severityLost Communication with Alternator/Generator Module
What U0118 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
Where to start: Modern smart alternators communicate on CAN or LIN bus. Check wiring and connector at alternator.
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