Another module reported that expected communication with the engine or powertrain controller was absent.
Why this matters
A trouble code reports a monitored result. It narrows the system and test conditions, but it rarely names the failed part by itself.
Evidence to capture first
- Which modules communicate now and which stored U0100
- Battery voltage history, controller powers and grounds
- Network bias voltage, resistance only when powered down as specified, and harness topology
A disciplined path
- Save a full network scan and code status
- Determine whether the ECM is offline or only one module lost its messages
- Load-test ECM powers and grounds before network disassembly
- Use the wiring topology to isolate branches without creating additional disconnect codes
Decision point
The repair is supported when the failed circuit, mechanical condition, or monitored response is measured and the original monitor can run without the fault returning.
Source desk
Use current model-specific service information for specifications, connector locations, disabling procedures, and tightening values. The following public resources support the broader safety or system context used in this guide.
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