# U0100 — Lost Communication With ECM/PCM

> ClearTheCode diagnostic code reference (not OEM service data).

Source: https://clearthecode.com/codes/U0100

**System:** Network · CAN Bus

**Severity:** severe

## Description

Module cannot reach the ECM/PCM. Check power/ground at the PCM and CAN bus wiring.

## Diagnostic snapshot

- **Difficulty:** 6/10 — Intermediate diagnostics
- **Est. repair cost:** $120 – $450

## Diagnostic workflow

1. Confirm U0100 with a live scan — note pending vs stored and freeze frame data.
2. Inspect wiring/connectors and related sensors before replacing modules.
3. Clear codes and road-test; re-scan after two drive cycles if the monitor must set.