U0100

Serious, act now

Lost Communication With ECM/PCM

What this code means

Other modules on the CAN network cannot communicate with the engine control module.

Common symptoms

No start or stalling
Multiple warning lights
Dead gauges

Most common causes

CAN bus wiring damage or corrosion
Failing ECM power/ground
Faulty ECM
Battery/charging problems

Can you keep driving?

Communication faults can cut the engine unexpectedly - treat as urgent, especially if symptoms are intermittent.

Do not guess in the dark

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Descriptions are for guidance only. Accurate diagnosis requires a workshop inspection.