U0100critical severityNetwork
Lost Communication with ECM/PCM
on 2002 BMW 525i 2.5L I6 M54 · RWD
What this code means
The diagnostic system cannot communicate with the Engine Control Module.
Symptoms
- Multiple warning lights
- Engine may not start
- Many systems inoperative
- Cannot read engine codes
Common causes
- PCM power or ground failure
- CAN bus wiring issue
- PCM failure
- Fuse blown
- Wiring harness damage
Diagnostic steps
- Check PCM fuses
- Test PCM power and ground circuits
- Check CAN bus wiring to PCM
- Try communicating with other modules
- Inspect wiring harness
Repair notes
Check fuses and power supply to PCM first. CAN bus issue is second most common.
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Other Network codes on this vehicle
CC-ID-181
System Check Failed
CC-ID-207
Central Electronics Failure, Stop 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