U0100 (generic)
Lost Communication With ECM/PCM
System: Network · CAN Bus
Severity: severe · Inspection: not flagged
Description
Module cannot reach the ECM/PCM. Check power/ground at the PCM and CAN bus wiring.
Diagnostic snapshot U0100
- Difficulty
- 6/10 — Intermediate diagnostics
- Est. repair cost
- $120 – $450 (parts + typical shop labor)
Diagnostic workflow
- Confirm U0100 with a live scan — note pending vs stored and freeze frame data.
- Inspect wiring/connectors and related sensors before replacing modules.
- Clear codes and road-test; re-scan after two drive cycles if the monitor must set.
Topics
- OBD-II and scan tools (guide)
- Network DTCs (U-prefix) (system)
Related symptoms
None linked yet.
Common fixes (curated)
None linked yet.
Related articles
None published for this code yet.
Diagnostic bundle (JSON)
Machine-readable graph: related codes, symptoms, fixes, topics, articles, and curated sources rows. Append &external=1 for optional YouTube / Google CSE hits when API keys are configured (see web/.env.example).