U0100 - Lost Communication With ECM/PCM

A module lost communication with the ECM/PCM.

Code Overview

A module lost communication with the ECM/PCM.

Common Causes

• Low system voltage
• CAN wiring/connectors issue
• Module power/ground issue
• Module failure

Diagnostic Steps

1. Check battery/charging system
2. Scan for multiple U-codes
3. Inspect CAN wiring/connectors
4. Check module fuses/grounds

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

Browse the closest code-family pages when the same fault pattern often shows up nearby.

Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.