U0115critical severityNetwork
Lost Communication with ECM/PCM B
on 2015-2019 Subaru Legacy 2.5L H4 · AWD
What this code means
Cannot communicate with the secondary Engine Control Module on vehicles with dual ECMs.
Symptoms
- Partial engine management failure
- Some cylinders not controlled
- Reduced power
- Check Engine Light
Common causes
- ECM B power failure
- CAN bus wiring
- ECM B failure
- Fuse blown
- Connector issue
Diagnostic steps
- Check ECM B fuse
- Test power and ground
- Check CAN wiring
- Try direct communication with ECM B
- Compare ECM A and B communication status
Repair notes
Dual ECM vehicles are less common. Check power supply to secondary ECM.
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