U0100Network
CAN network · SAE
Lost Communication With ECM/PCM
Meaning
CAN bus communication with the engine control module is lost. The other modules no longer receive the data they expect from the ECM/PCM.
Common causes
- Open or shorted CAN bus wiring or connector
- Failed engine control module or one with no power
- Module power-supply or ground problem
- Blown fuse on the ECM/PCM supply
- Water or corrosion in connectors
- Faulty CAN termination resistors or network interference
Symptoms
- Multiple warning lights at once
- No-start or limp mode
- Dead or inconsistent gauges/functions
- No communication with the module during diagnosis
- Abnormal behaviour of connected systems (ABS, transmission)
Severity
High: the vehicle may fail to start or lose essential functions and must be diagnosed immediately.
What to do
- Check the engine control module's power, ground and fuses
- Inspect the CAN bus wiring and connectors and look for water/corrosion
- Measure the CAN-High/CAN-Low lines and the termination resistors
- Confirm whether the module responds to diagnosis; if unpowered or failed, restore/replace it