Network · Severity: High
U0100 — Lost Communication With ECM/PCM A
One or more modules stopped receiving messages from the engine control module on the CAN bus.
Common symptoms
- Multiple warning lights
- No start
- Gauges dropping out
Likely causes
- ECM power or ground loss
- CAN wiring short or open
- Faulty ECM
- Low battery voltage
First test to run
Check ECM supply and grounds, then measure CAN bus resistance at the OBD port (about 60 Ω with ignition off).
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