U0101high severityNetwork
Lost Communication with TCM
on 2004 Subaru Legacy 3.0L H6 · AWD
What this code means
Cannot communicate with the Transmission Control Module.
Symptoms
- Check Engine Light
- Transmission in limp mode
- Harsh shifting or no shifting
- Trans warning light
Common causes
- TCM power/ground failure
- CAN bus wiring to TCM
- TCM failure
- Fuse blown
Diagnostic steps
- Check TCM fuses
- Test power and ground at TCM
- Check CAN bus wiring
- Try direct communication with TCM
Repair notes
Check fuses and power supply. Verify CAN bus.
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